AN ANALYSIS OF THE EFFECTS OF

FATIGUE AND SPECIFICITY ON

MOTOR LEARMNG

Tracey Lynn Kerr

B. A. (Psychology), McMaster University, 1 993

THESIS SUBMITTED IN PARTIAL FULFILLMENT OF

THE REQUIREMENTS FOR THE DEGREE OF

MASTER OF SCIENCE

in the School

of

Kinesiology

O Tracey Lynn Kerr 1998

SIMON FRASER UNIVERSITY

July, 1998

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AB STRACT

Two experiments were conducted to examine the influence of induced muscle fatigue on

motor performance and leaming. The goal of Experiment 1 was to examine physical fatigue as a

variable affecting performance andor leaming of a uni-limb rnotor task. Two groups practised an

aiming task until a critenon performance level had been achieved for temporal and spatial goals.

Prior to initiating the task, a fatigue group engaged in bicep curls and tricep extensions until a

fatigued state had been reached. A control group completed the task without being fatigued.

Both groups returned seventy-two hous later @ay 2) for fZty trials without feedback in a non-

fatigued condition. Results indicated that fatigue caused decrements in both Day 1 performance

and Day 2 performance, suggesting that fatigue acted as both a performance and a learning

variable. Expenment 2 was designed to examine the effects of fatigue on a more complex motor

task, and the specificity of leaniing hypothesis. Forty participants were randomty assigned to

either a fatigued or non-fatigued condition for a session of either 100 or 300 acquisition trials.

Seventy-two hours later participants returned and were again divided into fatigue and non-fatigue

groups, pnor to completing 50 retentiodtransfer trials. The task involved a complex senes of

extension and flexion movements at the elbow on a horizontal rnanipulandurn requiring both

spatial and temporal accuracy. The goal of the movernent was to replicate a criterion cunre that

was displayed on a cornputer monitor. Feedback was provided upon completion of each trial.

Participants were fatigued as in Expenment 1 with additional fatigue being interpolated &er

every 100 trials during acquisition. The data offer support for the specificity hypothesis in that

leaming and performing the task was supenor under similar proprioceptive feedback conditions.

Also, support was provided for fatigue as a leaming variable.

ACKNO WLEDGME3TS

There are many people who have helped guide me dong my path in Me over the course of my

graduate studies, but there are a special few which 1 would iike to mention here. My etemal

gratitude goes out to my supervisor Dan Weeks for his continual words of wisdom, support, for

believing in me and giving me the chance to pursue a dream. Digby EUiott, for believing that faith

and determination cm extend farther than possibly visible by others, and John Dickinson, for his

encouragement and honesty. To Chris Ivens, 1 extend my sincerest appreciation for his patience

and knowledge that made this thesis possible. 1 would also Like to thank Ian Franks and Paul

Nagelkerke fiom the School of Human Kinetics, University of British Columbia, and Dave

Goodman, for the use of their equipment and help in programming.

I have led a forninate He. My parents taught me as a child that when you believe in yourself

and your abilities that d things are possible. Thanks mom and dad for teaching me to dream big!

In my short time here on the west coast 1 have befnended many people who have intluenced my

life as much as my menton have ... my training buddies. Kudos to Catherine, Kim and rny other

dear fnends who spent many hours on their bikes, in their mnners, in the pool, at the lab or in the

pub listening, laughing and always supporting all my efforts.

Finally, sincere thanks to Shona McLean, Barb Peachey and Laune Klak for their

comedic relief and endless efforts.

TABLE OF CONTENTS

APPROVAL ...................................................................................................................

AB S TRACT .....................................................................................................................

ACKNO WLEDGMENTS .............................................................................................

TABLE OF CONTENTS ...............................................................................................

LIST OF TABLES ...........................................................................................................

LIST OF FIGURES.. .......................................................................................................

INTRODUCTION ..........................................................................................................

............................................... Fatigue and the Learning of Motor Skilis . . . .

..................................................................................... The Specfic~ty Pnncxple . .

Specuicity and Feedback ....................................................................................

EXPERTMENT 1 ............................................................................................................ . .

Participants ..............................................................................................

Task and Apparatus ...............................................................................

Procedure .................................................................................................

Data Treatment ........................................................................................

................................................................................................................... Results

. . ll

... 111

iv

v

vii ...

ml

1

2

8

10

15

15

25

16

17

17

.......................................................................................................... Discussion 20

.......................................................................................................... EXPERTMENT2 21

.................................................................................................................. Method 21 . .

Participants .............................................................................................. 21

Task and Apparatus ............................................................................. 21

Procedure ................................................................................................ 23

Data Treatment ....................................................................................... 24

Results ................~............................................~...~.~........~...................................... 25 . * -

............................................................ ........ Day 1 : Acquislt~on .... 25

Day 2: Retention/Transfer ...................................................................... 30

Discussion ............................................................................................................. - 3 8

GNE- DISCUSSION.. ...........................................................................................

................................................ Support for Fatigue as a Leaming Variable

Support for the Specscity of Motor Learning Hypothesis ....................

................................................................................................................... NOTES

................................................................................................................ REFERENCE S

............................................................................................................... APPENDIX A-

Ce11 means for Acquisition Phase ...........................................................

................................................................................................................ APPENDlX B

...................................................... Cell means for RetentionITransfer Phase

APPENDUC: C .................................................................................................................

.................................................................................... Infonned Consent Foms

LIST OF TABLES

Table 1 . DifFerences in the Fatigue and Motor Leaming Literature

Across Studies .................................................................................................. 7

. ..........................*..*....................... Table 2 Experimental Design for Experiment 2 24

LIST OF FIGURES

Figure 1. Group x Day interaction for Experiment 1 .............................................

Figure 2. Criterion curve. Four joint reversais requinng both spatial and

temporal accuracy were needed to reproduce this cuve ............................

Figure 3. Main effect for block for the measure of mean RMSE. ...........................

Figure 4. Three-way interaction: Acquisition Phase x Trials x Block

for the measure rnean RMSE ................................................................

Figure 5. Signincant main effect for block for mean RMSE for the

retentiodtransfer phase.. ......................................................................

Figure 6. Three-way interaction: Acquisition Phase x Transfer

Condition x Block for mean RMSE. ...................................................

Figure 5. Mean Tau (msec) three-way interaction: Group x Transfer Condition

Block, for retentiodtransfer phase ................................................................ 34

Figure 6 Variability measure for Tau (msec.), two-way interaction:

Group x Transfer Condition, for retentiodtransfer phase

in Experiment 2 ...........................................................................................

Figure 7. Standard Deviation values for Cross Correlation, two-way

interaction: Group x Transfer Condition, for retentionltransfer

phase in Experiment 2.. ...........................................................................

INTRODUCTION

The various types of motor skills that we have the potential to leam and perform are

endless. This impressive capacity to acquire new skills has led to a major interest in the manner in

which humans leam, the variables that are crucial in detemiining how humans gain knowledge

Eom practice and the context in which leaming takes place.

Any definition of motor learning should include a number of important features. First,

leaniing is a process that leads to an increased capacity for executing skilled action. Second,

motor learning is a fùnction of practice and/or expenence. Consequently, not al1 factors that yield

changes in behaviour can be attributed to leaming (e-g., growth and maturation). Next, since

learning is presumed to occur intemally, at the level of the nervous system, it must be inferred by

o b s e ~ n g changes in performance. Finally, changes in behaviour must be relatively permanent

and not easily reversed (Schmidt, 1988; Magili, 1993) in order to quali@ as leamed behaviour.

A traditional theme in the motor Iearning Literature has been to distinguish those

independent variables that influence leaming from those that do not. Variables that produce

immediate effects on performance wMe present but dissipate when the variable is withdrawn, are

considered perfrmance variables. Alternatively, in addition to atfecting performance while it is

present, a iearning variable continues to exert an influence on performance after it has been

removed, notably in retention/trmsfer tests. As weli as helping to advance motor learning

theory, knowledge regarding the relative effects of performance and learning variables can have

practical implications for teaching motor skills. For example, ascertaining that a aven variable

only affects performance can reiieve an instnictor fiom rnanipulating that variable in a training

protocol. Altematively, leaniing variables must be carefülly chosen and manipulated because they

directly influence the arnount that an individual will l e m .

Many of the variables which only influence performance and those which also affect

leaming are well documented. For exarnple, one of the most powerful motor learning variables

(other than practice itself) is the information about movement that is provided to the performer

d e r the movernent has occurred. The amount and type of this knowledge of results m) can

directly determine the extent of motor leaming. For example, Newell(1974; cf. Magili 1993) had

participants move a lever to a target in a cnterion movement time (MT) of 150 milfiseconds

(mec.). One group of subjects received KR on 52 of 75 trials, while a second group received KR

on only 2 trials. Results fiom the study indicated that for those participants in the first group, the

ski11 was well learned. Altematively, participants in the second group actually performed worse

across trials. Thus, KR appears to be critical in acquiring many skilis, as it d o w s one to set up a

reference point or standard to compare future movements against. Still other variables exist for

which the evidence is much less clear regarding leaming effects.

Fatigue and the Lemming of Motor Skills

Fatigue can be defined as "a state of the body characterized by weariness, during which there

is a clearly differentiated increase in perceived exertion" (Spano & Burke, 1976). A number of

experiments since the 1960s have investigated the role of fatigue in the learning of motor skills.

One prototypical experiment was conducted by Godwin and Schmidt (1 97 1). In their experiment,

participants were required to make a clockwise lever rotation through 350 degrees, reverse the

movement another 350 degrees and release the lever. This "sigma" task finished with a linear

movement to knock down a b h e r . Participants were put into two training conditions, fatigue

and non-fatigued. For the non-fatigued group, participants performed 20 trials, each separated by

a 45 second rest interval. The fatigued group performed an a m ergometer task both prior to the

practice session and between each of the 20 practice trials. Consequently, participants maintained

fatigue throughout the acquisition of the skill. Results revealed that fatigue clearly influenced

performance of the task as indicated by a 400 msec MT increase for the fatigue condition.. In

order to assess the relatively permanent changes in behaviour associated with learning, al1 the

participants completed the task again 3 days later for 10 trials under non-fatigued conditions. The

initial performance of the fatigued group remained depressed on the second day but the effect

dissipated quickiy over the 10 trials. In this study, the authors concluded that, at best, fatigue was

only slightly detrimental to leamuig the task. Collectively, however, the literature suggests that

although there has been considerable consistency regarding the effects of fatigue on performance

conclusions regarding l e d n g have been less clear.

Much of the literature on fatigue has examined the issue of whether fatigue has an

influence on an individualfs capacity to learn a particular task. Whereas some authors (e-g.,

C a ~ o n , 1972; Thomas, Cotten, Spieth, & Abraham, 1975) have found participants unable to leam

a task under fatigue conditions, others (Aiderman, 1956; Godwin & Schmidt, 1971; Spano &

Burke, 1976) have not found fatigue to be detrimental to leamkg. Given the considerable

differences amongst the studies that have investigated this topic ( e g , including design

dserences, level of fitness, measurement of fatigue, and the type of task used), it would seem

pertinent to review each study in greater detail. It may be that one or more of these factors

determines whether a performance or learning effect occurs with fatigue.

Alderman (1956), had participants complete either a "rho" motor or "pursuit" rotor

(single-limb) learning task. Both of these tasks require the participants to move their hand and

arrn through clockwise circular orbits as rapidly as possible. Two training conditions were

introduced halfway through the acquisition phase of the experiment. In the control condition,

participants rested for 10 minutes prior to completing the task, whereas in the experimental

condition, participants exercised on a rn ergorneter for 10 minutes. After two days of practice,

results indicated that fatigue impaired performance on both the rho motor and pursuit rotor tasks.

However, fatigue failed to affect the learning of the tasks.

Schmidt (1969) examined the relation between fatigue and the peiformance and learning

of a Bachrnan ladder climbing task. In that experiment the criterion task consisted of climbing a

"fiee standing" ladder (two parallel ladders situated with one side in comrnon and staggered

nings), as high as possible in a 30 second time period. The experiment was divided into two

separate days. On the first day, participants were divided into three groups (rnild exercise,

moderate exercise or mental task completion), and dl groups completed 10 Iadder climbing trials.

During a 90 second intertrial interval participants in the rnild exercise group rode a bicycle

ergometer at a workload of 750 kg rnhh for 75 seconds. Participants in the moderate exercise

group rode at a workload of 1200 kg mhin, while those in the mental task group engaged in a

vowel-cancelling task. On the second day, participants returned and completed four trials with a

30 second intertrial rest period. The results indicated that fatigue had an affect on performance

but not the learning of the task.

In a sirnilar study, Carron (1972) had participants complete a Bachrnan ladder climbing

task in a 20 second time period. Participants in the control group completed a vowel cancelling

task for 10 minutes. Participants in the experimental group rode a bicycle ergometer for 10

minutes at varying levels of intensity, until they reached a heartrate o f 180 beats per minute

(bpm). Al1 participants completed a total of 68 practice t d s across four days, with fatigue

interpolated for 2 minutes d e r each block of 18 trials for the experimental group. The retest

period consisted of two blocks of trials (trials 39 to 53 on Day 3 and 54 to 68 on Day 4), during

which time both groups executed the task without fatigue. Contrary t o Schmidt (1969), Carron

found that interpolated fatigue aEected both performance and leaming of the Iadder chb ing task.

In an experiment by Thomas et al. (1975), the eEect of severe fatigue on a stabilometer

balance task was examined. The task required participants to balance on a platfom situated on a

fulcrurn for a 30 second time period. On the first day of the experiment, participants either

walked on a treadmill for 5 minutes (experimental group) at varying levels of intensity to a heart

rate of 175- 180 bmp, or rested for 5 minutes (control group) pnor to completing two trials on the

stabilorneter. Alternating between exercise or rest, the criteion task continued until22 practice

trials were completed. On the second day participants returned and completed four consecutive

trials without exercise or rest intervals. The authon concluded that severe fatigue af5ected both

the performance and leaming of the stabilometer balance task.

Spano and Burke (1 976) investigated the effects of increasing work intensity (bicycle

ergometer) on the performance of a pursuit rotor task. On day one of the experiment,

participants completed twenty 30 second practice trials on the pursuit rotor task while cycling.

On the second day, participants maximum heartrate was deterrnined by increasing workloads until

the point of exhaustion. During days 3-5 participants had to complete five 30 second trials while

cycling for 10 minutes at either 60, 75 or 90% of their maximum heartrate.

The results indicated that as exercise intensity increased performance decreased, while leaming of

the task was apparently not af3ected.

As eluded to earlier, there are several factors that may contribute to why leamhg efects

were found in some studies, but not in others. For example, as pointed out by Fleury and Bard,

(1 987) inducing a "gross" state of fatigue prior to completing a Bachman ladder task (e-g.,

Carron, 1972) would clearly hinder one's balance, and thus atfect Iearning of the task. In

cornparison, studies (e-g., Godwin & Schmidt, 197 1) which used a more localized form of fatigue

(a single-lirnb via an arm ergorneter) failed to reveal a learning decrement. Thus, it is possible that

design differences, such as iducing single-limb as opposed to a gross state of fatigue, may affect

the appearance of a leaming decrement.

Affects of fatigue may also be moderated by a second factor, fitness. Fleury and Bard

(1987), investigated the eEects of fitness Ievels and fatigue on the performance of either a

cognitive or sensory-motor task. The authors hypothesized that central processing mechanisrns in

a sedentary population would be more disturbed by fatigue, than that of a fit population. In their

study, fatigue was induced by using four types of running eEort. Each experirnental participmt

was subjected to d l four types of running effort, and performed each ninning condition prior to

engaging in either the cognitive or sensory-rnotor task. Control subjects did not engage in the

fatiguing condition. The cognitive task consisted of recailing sequences of letters, whereas, the

sensory-motor task involved completion of a coincidence-anticipation task. Fleuiy and Bard

found that performance on the cognitive task decreased rapidly with increasing effort (fatigue) for

the sedentary participants. Conversely, performance was not affected for fit participants. As well,

performance on the sensory-motor task was significantly affectecl by maximal effort, with

participants consistently initiating motor responses prior to stimulus onset. The authors

concluded that a fit population is less aEected by fatigue than a sedentary population in terms of

performance.

Most of the earlier literature on fatigue and leaming failed to consider the individual

fitness level of the participants. Aiso, the measurement of fatigue across studies has been varied.

Although some studies have used heart rate as an indicator of fatigue (Carron, 1972; Thomas et

al., 1975; Spano & Burke, 1976), cardiorespiratory fatigue may not be filly indicative of, nor an

accurate estimate of muscular fatigue. Indeed, other factors including stress, temperature, illness

and genetics can play a role in the time course of cardiorespiratory fatigue, while not necessarily

directly aoecting muscle fatigue. Further, it has been argued that different energy systems are

used for cardiorespiratory and musculature systems (Wardlow, 1994). The muscular system

could become fatigued due to a lack of glucose readily available to the muscles and yet an

individual may still experience no cardiorespiratory effects.

Finaliy, whde motor abilities are generally considered to be specifk and independent

(Magill, 1993), the majority of the studies reviewed here (see Table 1) did not test for learning a

task that involved the same muscles used in the fatiguing task. This issue will be firther discussed

in the next section.

Table 1

Difikences in the Fatigue and Motor Learnin~ Literature Across Studies

Study Learning Performance Criterion Task Fatigue Task Level of Measure of Fitness Effect Effect Fatiguel Fatigue Considered

Alderman (1 956) 4

Schmidt (1 969)

no Y es Rho motor arm ergorneter liyht none no

no Yes Bachman ladder bike ergometer easylmoderate none no

Godwin & Schmidt (1 97 1) no Y es Pursuit rotor bike ergometer light HR 180 no

Carron (1 972) Yes Yes Bachman ladder bike ergometer heavy HR 180 no

Thomas et al. (1975) Y es Yes Stabilometer treadmill heavy HR 180 Yes

Williams et al. (1 976) nia Yes Bachman ladder step task moderatelheavy HR 180 no

Spano & Burke (1 976) no Yes Pursuit Rotor bike ergorneter moderatelheavy % of HR Y es

1. These are not objective assessments but rather are the levels of fatigue as defined by the respective authors.

The Specificity Principle

Historically, the specificity of training prînciple stems from the field of exercise

physiology. In order to maximize performance the training program must be relevant to the

demands of the task for which the participant is being trained. Any training done at a different

intensity fiom the critenon task, results in changes that are appropriate for that workload, but that

are not appropriate for the specined criterion performance (Bamea, Ross, Schmidt, & Todd,

1973). Furthemore, if one were to train on another task, the resulting muscular endurance would

be specific to that task, and inappropriate for the rnuscular endurance required for optimal

performance on the criterion task Daniell-Smith & Gunson, 1976).

In the area of motor leaming, specificity of training is conceptuaily consistent with

Henry's memory drum theory (Henry, 1958). The memory drum theory is based on three general

premises. Fûst, individuals maintain a large repertoire of abilities. Second, these abilities are

independent of each other. Finaily, the skiils we perfonn are dependent upon these abilities.

Henry also suggested that the transfer amongst skills would be very low. Further, the theory

assumes the existence of a memory store for motor programs. It is suggested that a learned skill

is supported by a specific motor program that includes the appropriate neuromuscular patterns

necessary to produce a desired result (Willams et al., 1976). If the motor task is changed even

stightly, it would be considered to be a new motor task, thereby requiring a new motor program.

In a study by Basmajian (1962), fatigue was shown to cause a change in the recruitment

pattern and intensity of motor units within a muscle. These resuits provide theoretical support

for Barnett et al. (1973), who found that a motor skill performed under fatigued conditions would

use a different motor program than that same task performed under non-fatigued conditions.

Presurnably, Leamhg would be most efficient when both the practice and performance conditions

were identical. In tems of fatigue then, it could be hypothesized that Ieaming would be optimal

when both the practice and criterion conditions were completed under either a fatigued or rested

state. Any other combination (e-g., fatigued practice with rested criterion) would produce a

learning decrement.

Numerous midies have tested this hypothesis, but have produced contradictory results.

Barnett et al. (1973), used a sigma task to contrast specificity of training with an optimal

conditions paradigm. Contrary to the specificity p ~ c i p l e , the optimal conditions view posits that

practice should occur under those conditions that produce the highest performance level. For

exarnple, if practising under a rested state aiways produced the highest level of performance,

relative to a fatigued state, then the reaed state would be considered "optimal". In the Barnett et

al. study participants practised the sigma task either in a fatigued or non-fatigued condition over

two days. On the first day, fatigue was induced by having the participants crank an arm

ergorneter for two minutes prior to the first trial, with 14 seconds of cranking during subsequent

intertriai intervals. Non-fatigued participants tapped a table top durhg the same intertrial

intervals. On the second day, participants returned to complete a further 10 trials, performing in

either the same or opposite condition as in day 1. Results indicated that practising under non-

fatigued conditions produced more leaming than practising under fatigued conditions. Therefore,

support was provided for leaming under optimal conditions and there was no support for the

specificity of training principle.

Williams et al. (1976) revisited the work by Barnett et al. (1973), but used a gross motor

task (E3achman ladder) to test the specidcity hypothesis. Participants were required to complete

54 practice triais on a ladder clirnbing task on each of four consecutive days. On days 1 and 3,

both the experimentd and the control group were fatigued using a stepping procedure prior to

practising the ladder climbing task. Fatigue was also interpolated afker each trial to ensure no

recovery had taken place. On day 2, the control group continued to practice the criterion task

while in a fatigued state, whereas the experimental group practised under non-fatigued conditions.

On the final day both groups practised under non-fatigued conditions. In contrast to the Barnett

et al. (1973) study, Williams et al. found support for the specificity hypothesis. Thus, practising a

task under conditions of heavy fatigue facilitated performance of the critenon task when

completed under similar conditions of fatigue.

The reason for these contradictory results might be sitributable to either the level of

fatigue induced, the type of task used, or both. As pointed out by Thomas et al. (1975), the

fatigue associated with high intensity exercise is known to cause characteristic changes in an

electromyograph signal whereby an increase in amplitude and a slowing of the discharge rhythm

occurs (possibly indicating a change in the associated motor programming). It is possible then,

that oniy under high levels of fatigue are changes in the motor task sufficient to require a new

motor prograrn. Thus, high levels of fatigue may be a prerequisite to showing specificity effects

and a leaming effect.

It is important to point out that the studies that have filed to £ind support for the specificity

principle (Godwin & Schmidt, 1971; Barnett et ai, 1973) used a single-limb motor task. It may be

that with single-hb tasks ody the limb in use is fatigued, thus the state of fatigue may not be as

lasting as in a gross motor task. Moreover, as ody one limb was used, a greater level of fatigue

rnay have been required to induce a change in the motor program. The studies reviewed earlier

pertaining to fatigue and motor leaming generally have not addressed the issue of specincity in

terms of either the task or the muscles used. in studies conducted by Alderman, (1956), Godwin

and Schmidt, (1971), Spano and Burke, (1 W6), the authors fded to test the effect of fatigue on

the specific muscle groups that were to be used in the task (see Table 1). The fact that other

muscles (e-g., a gross state of fatigue was induced) were also fatigued during practice, aside korn

the specific muscles to be used on the task may have interîered with the emergence of a leaniing

effect. Moreover, the fatiguing task was different from the critenon task that participants had to

perform. The specificity principle dictates that training activities should involve the same muscle

groups and simulate as closely as possible the movement patterns that occur during actud

performance (Fox, Bowers & Foss, 1993).

Specificity and Feedback

The role that feedback plays in relation ta rnotor leaming has been a topic of considerable

interest since the turn of the century. Two theories have been proposed regarding the control of

movement, open vs. closed-Ioop -stems. Essentially, with an open-loop system, feedback

(afferent information) is not required to carry out a movement. Rather, movement is conduaed in

an al1 or none fashion. Presumably, within an open-loop system there exists a control center or

executive (Magill, 1993) containing al1 the information necessary for the effectors to carry out a

particular movement (Magill, 1993). Feedback, although available, is not required to execute an

ongoing movernent sequence.

Altematively, error detection and error correction made possible by feedback play a key

role in closed-loop control. The movement control center in this case is based upon a reference

system that specifies the desired outcome or value for the system (Adams, 1971). Output fiom

sensory receptors is compared against the reference to determine whether or not

adjustment in the movement is required. Thus, a closed-loop system is self-regulatory, in that,

assessing, detecting and correcting of error occurs continuously. In order for motor leaming to

occur, developing the reference mechanism must occur so that one will recognize when a

movement has been performed correctly.

Adams (197 1) expanded upon the idea of a closed-loop system of motor control.

According to Adams, movement consists of two parts: initiation, and movement d e r initiation

has begun. Movement initiation is anaiogous to an open-Ioop system, Adams referred

to the initiation phase as a "memory trace". As with an open-loop system, no feedback is required

for evoking the memory trace. Not until movement has started is feedback generated by the

sensory receptors. Once movernent has begun a "perceptual trace" is calied up, which is

consistent with a closed-loop system for motor control. The perceptual trace is used to not only

assess movement in progress, but also to determine when to terminate movernent. Essentially, the

movement currently being executed is compared to what was intended, with adjustments in the

movement patterns continuing until a perfect match exists. The determination of necessary

adjustments in movement patterns is based on both interna1 (afferent) and external sources of

information. With increased practice cornes a strengthening of the percephial trace, at which

point the individual has attained a "motor stagef' and no longer requires external feedback sources

to regulate movement. Finally, Adams contended that rnovement is not exclusive to either an

open or closed-loop system, rather that both are needed.

In order to push motor leaming theory beyond the simple limb positioning tasks used to

develop Adams (1 97 1) theory, Schmidt (1 975) put forth a schema theory. Generally, schemas

are a conceptuai entity that applies to a class of behaviour, not one behaviour in particular. A

schema cm be regarded as a rule or set of niles used in making a decision. These rules are

developed based on information gathered fiom the environment and through past experiences, and

are used in concept identincation. For example, in determinhg if an object is a chair, one would

refer to the rules that would d o w for the proper response. Schmidt expanded his schema theory

to include two control components; the generalized motor program (GMP), which consists of the

memory representation of a class of actions to be controlled, and the motor response schema

which provides the spec5c rules for action. In relation to feedback, a class of schemata termed

"recognition schernata" exist under the urnbrella of motor response schemata. The role of these

former schemas involves, as is the case in a closed-loop system, cornparison of existing sensory

feedback to expected feedback. Finally, information stored in memory is used to determine,

assess and control movement patterns.

For Adams' closed-loop theory, information feedback is essential to leaming. More

clearly, learning is optimized under conditions where continual feedback is provided.

Nternatively, with a GMP as proposed by Schmidt, once a movement is lemed, feedback is no

longer required to produce that movement. Given the importance and varied role of feedback in

both of these influential theoretical positions, it should not be surprising that a particular area of

concern in the contemporary motor skill literature concems what specifk sources of feedback are

rnost relevant to learning and performance. At issue are the types of feedback information (e-g.,

visual or proprioceptive) used, as well as what stages in processing feedback (e-g., earIy or late)

proves to be the rnost beneficial-

One prototypical experiment in examining the type of information used in leamhg and

controlling movement was conducted by Proteau and colleagues (Proteau, Marteniuk, Girouard,

& Dugas, 1987). They sought to determine whether on-going vision (of the limb) facilitated

performance on a manuai aiming task. As well, the effects of removing feedback (vision) afker

extensive practice was examined. Proteau et al. hypothesized that the elirnination of vision would

lead to a leaming decrement, especidly after extensive practice. The task involved an aiming

response to the center of a target 90 cm away. Four groups were divided into two separate trial

conditions, completing either 200 or 2000 trials, and two vision conditions, having either full

vision of their limb and target, or no-vision. Upon cornpletion of the practice trials aU participants

engaged in 20 test trials with no-vision. The authors concluded that performance was enhanced

when full vision was provided, regardless of trial condition. However, this performance level was

not maintained when vision was removed. It was this finding that prompted the authors to posit

a specificity of leaming hypothesis. Analogous to the specificity of training hypothesis,

consistency in the af3erent feedbâck sources is necessary for optimal performance and learning of

a task. Further, the authors posited that a sensorimotor representation exists for movement

based on information fiom both central processes and sensory feedback sources.

In an attempt to replicate the findings of Proteau et al., (1987), a sirnilar study was

conducted by Elliott and Jaeger (1988). However, these authors included a 2 second Lights-off

condition pnor to participants initiating the movement sequence. Reasoning behind the 2 second

Lights-off condition related to the concept information decay. Any leaming about the "position of

the target would be important since any visual representation of target position would ... decay

pnor to movernent initiation" (EIIiott & Jaeger, 1988). Participants completed 70 acquisition

trials in either a fiil1 vision, no-vision, or decay condition prior to transfemng to a dinerent

condition. Their results indicated that if one iearned the task in a fidl vision condition, withdrawal

of that information disrupted performance of the task. Likewise, and more irnportantly, if one has

learned the task without visual feedback, the addition of such feedback also disrupted

performance. These findings concurred with the finding of Proteau et al., supporting the idea

that movernent control becomes increasingly dependent on sensory feedback across tirne.

Proteau, Marteniuk and Levesque (1 992) revisited both their own earlier work and that of

Elliott and Jaeger (1988) to expand upon their hypothesis. Unlike the previous studies Proteau et

al. investigated the effects of adding (rather than removing) relevant sensory information to a

movement task which had been learned initially without this sensory information. The procedure

was consistent with the Proteau et al. (1987) study with the exception that subjects completed

1200 trials, and that vision was added after extensive practice in the no-vision condition. Proteau

et al. found a learning decrement associated with practising a movement without vision followed

by transfer to a condition with vision avaiiable. It was suggested that the addition of visual

feedback may have interfered with what had previously been leamed. That is, the sensorimotor

representation had developed in the absence of visual feedback and thus could not integrate that

type of feedback when provided during transfer.

Collectively, these studies (Proteau et al., 1987; Elliott & Jaeger, 2988; Proteau et al.,

1992) attest to a modality-dependent representation of movement which is integral to a specificity

of learning hypothesis. It appears that practising and learning a movement are tied to the sensory

feedback sources available during practice, and the rernoval, addition or alteration of subsequent

sensory feedback would result in a learnhg decrernent.

The argument put fonvard here is that learning under either conditions of non-fatigue or

fatigue would Iead to dBerent spec8c proprioceptive feedback conditions. For example, fatigue

may provide a different source of proprioceptive feedback. Thus, the proprioceptive feedback

would be different for someone who had initially practised a task under fatigued conditions and

then transferred to a non-fatigued condition. Therefore, a leamhg effect would be produced

analogous to that seen in previous studies by Proteau and coileagues under visionho-vision

feedback conditions.

This thesis investigates how fatigue affects the learning and performance of a fine motor

skiil, and in dohg so will address the following issues. First, is the influence of fatigue on learning

mediated by the arnount of practice? As well, is there a role for the specificity of learning

hypothesis in relation to fatigue and motor ski11 leaming?

EXPERTMENT 1

The purpose of Experiment 1 was to determine if fatigue af3ects the leamhg of a motor

skilï. To that end, an attempt was made to address shortcomings present in previous studies.

First, participants were fatigued based on individual fitness levels. As opposed to other studies

(Canon, 1972; Thomas et al., 1975; Spano & Burke, 1976) which used cardiorespiratory fatigue

as an indication of rnuscular fatigue, fatigue in the present study was defined by failing to reach a

personal criterion performance level during the fatiguing task. Further, specific muscle fatigue

was induced rather than "gross" or whole body muscle fatigue. As well, a single-limb rather than

gross motor ski11 was used as a means of locaiizing fatigue. This ailowed the experimenter to

relate the effects of fatigue to the specific lirnb rather than to the result of overdl weariness.

Finally, participants had to reach a critenon performance level prior to a retention test to ensure

that an equal level of performance had been reached by all participants.

Method

Participants

Ten participants (5 men and 5 women), ranging in age from 18 to 30, were randomly

assigned to either a control or an experimental group. Due to the nature of the task, ody

participants with no previous weight-lifting experience were used. Each participant was paid

$10.00 for their part in the study.

Task and Apparatus

Using a manipulandum, participants made forearm extensions in the horizontal plane

through a range of 60 degrees with the right arm. The manipulandum consisted of a horizontal

lever positioned at shoulder height, which had a vertical handle at one end and was attached to a

bearing-mounted vertical sh& at the other. The right foream of each participant was positioned

on the lever such that the elbow was coaxial with the axis of rotation. The position of the vertical

handle was then adjusted to accommodate for the length of ezch participant's forearm.

Participants grasped the handle with hidher hand in a supinated position. In an attempt to keep

contribution from the shoulder movement constant across ali participants, participants were

secured to the seat with a shoulder harness and their forearms were attached to the horizontal

lever with Velcro straps.

The target appeared on an oscilioscope screen that was positioned 70 cm directly in fiont

of each participant. The angular position of the rnanipulandum was sampled at a rate of 1000 H z ,

with the use of an optical encoder (Dynapar E20-2500-130) and a custom made computer

interface card. In addition, angular acceleration data were obtained kom a Kistler accelerometer

(type 8638B50, + 50 G) which was positioned at the end of the horizontal lever, 42 cm Eom the

axis of rotation. The signal from the accelerometer was filtered with a 50 Hz active lowpass filter

(Krone-Hite, #3 750) and sarnpled at 1000 Hz. EMG was recorded on the biceps and triceps

muscles to ensure they were active during the experiment.' The experiment was controlled by a

386-33 MHz computer (programmed in Borland Turbo Pascal 6.0) which also couected and

saved al1 data.

Procedure

Each participant attended one acquisition session that lasted approximately two hours and

then returned seventy-two hours later for a retention test which lasted approximately ten minutes.

At the beginning of the acquisition session the experimenter described the task and obtained

informed consent from the participant. Participants were then randomly assigned to either the

experimentd or control group. Participants in the experimentai group then engaged in varying

sets (10-12 repetitions each) of biceps curls and triceps extensions at 70-80% of maximum weight

on one lift, as determined by pretesting on Day 1. Participants altemated between the exercises

until they could no longer complete 5 successive repetitions. No rest was given between the sets.

Participants in the control group did not engage in the fatiguing task. The participant was then

secured in the shoulder harness, EMG electrodes were attached to the skin on the short head of

the biceps brachii muscle and on the lateral head of the triceps brachii muscle, following standard

EMG procedures (Basrnajian, 1974) l .

A low tone of 1000 Hz served as the waming stimulus. Following a variable foreperiod of

500-3000 msec., a higher tone of 2000 Hz served as the imperative stimulus. Participants were

instnicted to react to the 2000 Hz tone and in one movement move the cursor as accurately as

possible to a target 5 1.8' in width at a distance of 60° fkom the home position on the

osciIloscope screen. AU participants carried out the movement fiorn flexion to extension.

Participants had to complete the movement to the target within the range of 230-260 rnsec for it

to be counted as a successfÙIIy completed trial. Participants practised until they reached a

critenon of -50 (10 out of any 20 trials within the given MT) at which point the experïrnent ended.

Verbal feedback was given to each participant as to whether they overshot or undershot the

temporal criterion, and on-line visual feedback was also provided on the oscilloscope screen so

that participants could see if they hit or missed the target. A hit, as determined by the

experimenter, occurred when the participant landed within the target width 51 -8" in diarneter and

60° from the home position, and a miss being anything that did not land within the target width.

Participants were required to both hit the target and do so within the temporal critenon of 230-

260 rnsec for the trial to count as a good trial.

There were two dependent measures: temporal error, and spatial error. Temporal error

refers to the difference fiom the actual MT and the criterion MT. Error was determined on the

basis of the participants' ability to hit the target. The number of target misses spatially were

compared with the total number of trials completed. The fatiguing task was again introduced

after 100 trials for the experimental participants, in order to ensure that they remained in a

fatigued state.

Ail participants retumed seventy-two hours later to complete fifty non-fatigued retention

trials without verbal feedback-

Data Treatment

Analyses of the data were carried out either using analyses of variance (PLNOVA)

measures or t-tests. An alpha level of -05 was used for dl statistical tests. Al1 post-hoc

cornparisons used Tukey's HSD (alpha = -05).

Results

EMG records were examined and con£irmed that both the biceps and triceps muscles were

actively recmited under both conditions of fatigue and non-fatigue. A significant performance

effect (t = 2.555), p < -03 was found between the number of successfûl trials it took to reach

critenon. Participants in the experimentd group took significantly more trials (M = 377) to reach

the same level of performance as participants in the control condition (M= 173).

A 2 x 2 ANOVA (Group x Test Phase) with repeated measures on the second factor was

used to assess Leaming effects. The dependent measure analyzed was the number ofgood trials

(accurate both temporally and spatidly) cornpleted. A main effect for group E(1, 8) = 5.523, p <

-05 was found indicating that the participants in the experimentd group (M = 3 -2) performed the

task less efficiently than the control group (M = 13). A main effect was found for test phase F(1,

8) = 26.3 5 1, g c .O0 1. Au participants demonstrated supenor performance during the acquisition

session than during the retention session. A significant interaction was also found a l , 8) =

1 1.560, g < -009, and is shown in Figure 1. Although performance of the experimental and

control groups was nearly equal during acquisition (experimental: M = 15.6, control: &$ = 161,

fatigue impaired leaming of the task, revealed by the experimentd group's decreased capacity îo

complete an equal number of good trials on Day 2, compared to the control condition @ = 3.2;

M = 13, respectively).

A 2 x 2 ANOVA was also used to anaiyze temporal and spatial error. Neither measure

revealed significant main effects or interactions

Figure 1. Group x Day interaction for Expenment 1 .

Discussion

In contrast to the findings of Alderman (1956), Godwin and Schmidt (1971), and Spano

and Burke (1976), the resdts from the present study provide support for a leaming effect

associated with fatigue. The success of the present experiment, where others have failed, could

be attributable to several factors. First, by fatiguing the specific muscles to be used in the task

one can be assured that the effects of fatigue were localized. Also, by taking into consideration

the fitness level of subjects and faîiguing thern based on that level, one can have greater

coddence that al1 subjects reached the same state of fatigue. Finally, by using a criterion measure

to ensure that al1 groups reached the same Level of performance pnor to a transfer or retest, an

equai opportunity for leaniing was provided across groups. Thus, the results of Experiment 1

concur with those found by Carron (19721, and Thomas et ai. (1975), in that a learning decrement

was found d e r leaming under fatigued conditions. The present study was unique however, in

that it looked at the relation between specific muscle fatigue and the leaming of a single-limb

(fine) motor skill, whereas the previous studies by Carron, and Thomas et al. looked at the

relation between gross motor fatigue and performance on a "whole body" balance task.

While the evidence of Experiment 1 suggests that fatigue can have an impact on rnotor

Ieaming, the underlying rnechanism for the leaming decrement is still to be determined. It is

possible that inherent in the fatigue process is a less accurate or more variable transmission of

neural signals. The evidence f?om neurophysiological studies is inconsistent, but there is no doubt

that fatigue generates change in motoneuron firing (Bawa, Sogaard & Walsh, 1997). It is

possible that poorer leaniing under fatigued conditions is therefore a refiection of this change in

neurophysiological response.

EXPERIMENT 2

In addition to extending Our examination of fatigue and motor learning to a more complex

motor task, Experiment 2 was designed to examine the applicability of the specificity of learning

hypothesis (Proteau, 1992) to the issue of fatigue and motor skill leaming. Specifically, leamkg

should be optimal when the task is performed under conditions that are consistent with the

proprioceptive feedback that was used to develop a sensorimotor representation of the movement

dunng acquisition. For example, ifone is to perform the motor task in a non-fatigued state,

ultimately then it would be best to leam the task in the same state. The s m e prediction would

hold for a fatigued state. Either combination of acquisition and retention phases that do not

maintain consistent proprioceptive sensory feedback conditions would produce relatively poorer

results. For Experhnent 2, the task required subjects to l e m a sequence of flexion-extension

movements necessary to replicate a critenon curve which was briefly displayed on a computer

screen.

Method

Participants

Forty participants (20 men and 20 wcmen) from Kinesiology classes at Simon Fraser

University participated in this experirnent. Due to the nature of the task, only participants with no

previous weight-lifting experience were used. AH participants were right handed, as determined

by self report. Al1 participants were included in an experimental lottery draw for an opportunity

to win $500.00.

Task and Apparatus

A manipulandum consisting of a horizontal lever fixed with a vertical handle at one end

and attached to a bearing-mounted vertical sh& at the other was used to record the participants'

movement uiformation. The left forearm of each participant was positioned on the lever such that

the elbow was coaxial with the axis of rotation and the position of the vertical handle adjusted to

accommodate for the length of each participant's forearm. Participants grasped the handle with

their hand in a supinated position.

Using the manipulandum, participants made fore- extensions and extension-flexion

movements in the horizontal plane through a range of 60 degrees to replicate a criterion

waveform. The waveform appeared on a colour monitor that was positioned 0.75 metres directly

in front of each participant. The waveform was calculated spatiaily by the following formula

f(x) = -[sin(OSx) + sin x +- sin (2x)J and had a temporal duration of 2.2 seconds, which remained

constant across d l participants. The summation of these three sinusoidal waveforms produced an

asymmetncal form (see Figure 2) which has been used in other studies of both cognitive and

perceptual processes that occur during motor control and leaming (e-g., Ivens 1996).

r i (ma)

Figure 2. The criterion curve. Four joint reversais requiring both spatial and temporal accuracy were needed to reproduce this curve.

The analog data fiom the manipulandum was sampled at a rate of 50 Hz fiom a Hewlett-

Packard 33 10A fùnction generator. Custom software calculated the root-mean-square error

(RMSE) used for feedback, collected data on temporal and spatial shifts, and controlled the

timing and presentation of the criterion curve.

Procedure

On day 1, participants were randomly assigned to one of four conditions created by

combining two fatigue conditions (fatigue, and non-fatigue) with two levels of practice (100 trials,

or 300 trials). Participants were asked to read and sign an informed consent which gave a bnef

summaiy of the experiment. A verbal description of the experiment dong with information on

how to complete the task was also given. Prior to beginning the practice trials, al1 participants

completed ten familiarization trials. This d o w e d for exploration of the movement environment

and also enabled participants to view how these movements corresponded to the criterion curve

on the computer screen. During these farniliarization trials however, a solid horizontal line instead

of the criterion curve was shown on the computer screen and, unlike during the practice trials,

participants received on-line kinematic feedback.

Participants in the fatigue conditions engaged in varying sets (10-12 repetitions each) of

biceps curls and triceps extensions at 70-80% of their maximum weight for one repetition.

Maximum weight was determined at the begïnning of the first session for each participant.

Participants alternated between the exercises until they could no longer complete 5 successive

repetitions. After approximately four sets, a one minute rest was given to the participants before

continuing with the fatiguing task. Fatigue was fbrther induced after 50 trials for participants in

the 100 trial condition, and after 100 and 200 trials for participants in the 300 trial condition.

Participants in the non-fatigue conditions did not engage in the fatiguing task.

A trial consisted of three phases. In the first phase the critenon curve was displayed on

the monitor as a red colored wavefonn for 1.5 seconds. The criterion curve remained consistent

for al1 participants. The second phase began when the curve cleared fiom the screen. At this

point participants had to wait 1 second after the blanking of the monitor prior to initiating their

movement sequence. A threshold of 2" for movement of the manipulandum was set. Therefore,

once a participant initiated a movement, it took approximately 2.2 seconds to cornplete the

movement sequence, at which point data collection for that trial ceased. In all conditions no

on-line visual feedback was provided. The final phase of the trial consisted of terminai feedback.

Participants were shown their produced image of the curve superirnposed upon the cnterion

image. Also, shown in the bottom left hand corner of the screen was the RMSE score for that

movement. This feedback stayed on the screen until participants were ready to begin the next trial

at which point they depressed the space bar on the keyboard, which blanked the screen. Testkg

times ranged fiom one to two hours depending on trial condition (100 or 300 trials). Each

participant returned seventy-two hours later to complete a retentiodtransfer session which lasted

approximately ten minutes.

Table 2

Experimental Design for Experïment 2

Acquisition Condition na Trials Retention/Transfer Condition ab

Non-fatigued 10

Fatigued IO

Non-fatigued 10

Fatigued 10

100 Non-fatigued

Fatigued

100 Non-fatigued

Fatigued

3 00 Non-fatigued

Fatigued

3 00 Non-fatigued

Fatigued 5

Note. aNurnbers are total participants out of 40. For retentionhansfer

bpa.rticipants were divideci, and cornpleted either a non-fatigued or fatigued

condition.

On day 2, each of the groups were further split into either fatigue or non-fatigued conditions pnor

to completing the retentiodtransfer session (see Table 2). Participants in the fatigue condition

completed the same initial fatigue protocol as those participants who were fatigued on day 1,

except that fatigue was not interpolated during the retentiodtransfer trials. Al1 participants

cornpleted fi@ trials, with the cnterion cuwe and feedback conditions remaining the same as on

day 1.

24

Data treatment

Displacement data were filtered with a high cut off fiequency of 7 Hz using a second order

dual pass Butterworth filter. Analog position data sampled at 50 Hz on a 486 microcomputer

were transformed into a configuration cornpliant with the in-house software on a Sun station.

Each triai was visually inspected to see if participants either began the movement incorrectly (e.g.,

in the wrong direction) or initiated the movement abruptly (e.g., failed to wait the 1 second) , if so

that trial was discarded. Four dependent measures were analyzed in this study; cross-correlation,

maximum cross-correlation, tau, and root rnean square error (RMSE). Cross-correlation assessed

the amount of temporal shift fkom the produced curve to the cntenon curve. Maximum cross-

correlation assessed the point at which the correlation between the two curves was the best

spatialiy (e-g., learning the general shape of the criterion curve) and corresponding temporal shifis

looked at the cntenon movement over the produced movement to provided information regarding

overall spatial and temporal performance. Temporal shifi of the two curves was compared in 20

increments in either direction for a 20 rnsec interval (+MO0 msec). This is referred to as Tau

(rnsec). Finally, RMSE (degrees) was calculated to assess the overall error for the participants'

movernent in cornparison with the criterion movement. Variability associated with each of the

four dependent measures was dso analyzed.

Analyses of al1 data were carried out using analyses of variance (ANOVA). Cross-

correlations were transformed into Fischer-Z scores for statisticd analysis. The natural log was

taken for al1 W S E data to create a more normal distribution which is better suited for hrther

statisticai analysis. A Tukey's HSD procedure was used to fùrther investigate significant effects

revealed by the ANOVA. In an attempt to prevent problems fiom occumng due to missing data,

a missing or discarded trial was replaced by the mean value for that block of scores. With regard

to the variability analysis, the within subject values for standard deviation (SD) were calculated

including any missing or discarded data for that block, so as not to artificially lower the standard

deviation.

Because only certain data were pertinent to the research questions being asked, only portions

of the data were analyzed. Practice trials consisted of fve blocks of 10 trials equaily spaced

throughout. The pwpose of dividing trials into blocks was to show the progression of learning

across practice trials. For participants who completed 100 trials, blocks were formed Eom trials

1 - 10,3 1-40, 5 1-60? 7 1-80 and 9 1 - 100. For the 300 trial conditions block were fomed from trials

1 - 10, 7 1-80, 15 Z -1 60, 22 1-23 0, and 29 1-300. The 5 blocks for the retention condition, included

trials 1-1 0, 1 1-20, 2 1-3 0, 3 1-40 and 4 1-50 (see Romanow, 1984; Ivens, 1996). Analysis of the

retentiodtransfer trials was used to assess the amount of leaming that occurred in the different

conditions. An alpha level of -05 was used for d l statistical tests.

Results

The results section is divided into two sections corresponding to the Acquisition Phase, and

the Retentio flransfer Phase.

D ~ Y 1 : Acquisition Phase

Al1 dependent variables for the Acquisition Phase were analyzed using a 2 x 2 x 5 (Group x

Trials x Block) ANOVA with repeated measures on the last factor. The analysis of RMSE

yielded a main effect for block, E(4,144) = 56.92, p < .00001. Post hoc analysis revealed that

error decreased reliably across al1 5 block of acquisition, with the largest improvernent occurring

eom blocks 1 to 2 (see Figure 3). No other significant main effects, either for group, I31, 36) =

1.55, p > -21, or trials, E(l, 36) = 1.55, 2 > -22 were found. A significant Group x Trials x BIock

interaction was revealed, E(4, 144) = 4.53, 2 < -002 indicating that the way in which practice

interacted with fatigue condition depended upon whether the participant completed either 100 or

300 trials (see Figure 4). Specifically, participants in the 300 trial group performed better later in

practice (Block 3-5) when they acquired the task under conditions of fatigue. Participants in the

100 trial group by cornparison, remained relatively unafEected by acquisition condition in that

performance improved relatively consistently regardless of whether participants were acquisition

condition.

2 3

BLOCK

Figure 3. Main effect for block for the measure of mean RMSE.

NON-FATIGUE FATIGUE

1 2 3 4 5 BLOCK BLOCK

Figure 4. Three-way interaction: Acquisition Phase x Trials x Block for the measure rnean RMSE.

The andysis of Tau revealed no significant main effects for group, E(1, 36) = 1 . 1 7 , ~ > -28,

trials, c(1, 36) =.25, g > -61, or block, F(4, 144) = 2.04, g > -09, nor any significant interactions.

For the SD of Tau, a main effect was found for block, l?(4,144) = 47.88, p c -0001, indicating that

more timing variability was evident for the first block ( M = 229.7) than any of the other 4 blocks

(1 14, 1 12.2, 100, 9 1.1). No other main effects or interactions reached statistical significance.

For the analysis of maximum cross correlation, the results of the ANOVA on the means

indicated a significant block effect, E(4, 144) = 52.68, p < -0001, with the 5 r s t block a = .784)

being the least correlated spatiaily in relation to the cnterion and petformance cuve overlap, as

compared to the subsequent 4 blocks (1.412, 1.466, 1.557, 1.554). Neither the main effect of

group, E(1, 36) = .76, p > -38, the main effect of trials, E(1, 36) = -10, g > -74, nor any of the

interactions were statistically significant. The mean within-subject SD for maximum cross

correlation revealed a main effect for block, E(4, 144) = 25.25, p < -0001. Block 1 (hJ = -230)

was significantly more variable than al1 other blocks (-095, -124, -075, .074), which again were

not dinerent fiom each other. There were no other significant main effects or interactions.

The analysis of cross correlation revealed a significant main effect for block F(4, 144) =

56.39, p< -000 1. Block 1 a = -450) was significantly less correlated compared with al1 other

blocks (1 -040, 1.099, 1.2 16, 1 .224), which were not different fiorn each other. Again, no other

main effects or interactions attained statistical significance.

The results of mean within-subject SD for cross correlation yielded a main effect for

block, F(1, 144) = 29.97, g < .O00 1, indicating that the first block (M = -3 67) had greater mean

within-subject variability than the other blocks (. 178, -196, .130, .128), which were not different

From each other. No other significant main effects or interactions were evident.

Day 2: RetentiodTransfer Phase

As is typical in learning experiments, the last block of trials for the acquisition phase was

analyzed in conjunction with the five blocks from the retentionkransfer phase. Thus, a 2 x 2 x 2 x

6 (Acquisition Phase x Trials x Transfer Condition x Block) ANOVA was used in the following

analyses.

For the analysis of RMSE a main effect for block was revealed E(5, 1 60) = 14.3 0, g <

-00001 indicating that al1 subjects reliably improved across the 5 bIocks of retentiodtransfer (see

Figure 5) . Further, clear evidence of a performance decrement was evident as al1 participants

displayed a signifcant decrease in performance fiom the final block of acquisition (Block 1) to the

first block of retentiodtransfer (Block 2). A significant Acquisition Phase x Transfer Condition x

Block three-way interaction was also revealed, E(5, 160) = 2.87, p < -02, indicating that the way

in the transfer condition interacted with practice was dependent upon acquisition condition.

Specifically, participants who acquired and completed the task (during retentiodtransfer) under

sirnilar conditions of fatigue (NF-NF, F-F) outperformed those participants for which the fatiguing

conditions difFered (see Figure 6). No other significant main effect or interactions were revealed.

For the measure Tau, a significant Group x Transfer Condition x Block interaction was

found, F(1, 160) = 2.606, p < -05, and is shown in Figure 7. Again, because this interaction

includes both the block and transfer condition factors, Block 1 is rendered meaningless.

However, in the present case the locus of the interaction appears to dwell entirely in the first

block of retentiodtransfer (Block 2). Specifically, when transferred to a NF condition,

participants who had initidy acquired the task under NF tended to exhibit a temporal lag (falling

behind the cntenon) in movement, whereas participants who had acquired the task under F

conditions exhibited a temporal lead (ahead of the criterion) in movement. Conversely, upon F

transfer, participants who acquired the task under F conditions experienced a near zero tau value

(indicating perfectly timed movement), while those who acquired the task under NF conditions

demonstrated considerable lag in movement. These differences evident in Block 2 were no longer

present for the remaining retention/transfer blocks, and al1 participants regardless of acquisition

condition exhibited relatively stable temporal performance that generally tended to lead with

respect to the criterion. A Group x Trials x Block interaction just fded to reach significance,

F(l, 32) = 4.10, E < -051. AU other main effects and interactions were not statisticdy significant. -

The mean variability for the measure Tau yielded a main effect for block, E(5, 160) =

12.966, g < -000 1. Greater error was observed in Block 2 (M = 153 .X), compared to Block 1

@ = 9 1. l), and Blocks 3 through 6 (100.89, 9 1.39, 89.7, 72.02). Of most interest is the two-

way interaction of group and transfer condition, E(1, 32) = 4.32, p < -05, and is presented in

Figure 8. The least temporal error in retentiodtransfrr was observed for those conditions that

were consistent with regard to the F condition encountered during the acquisition phase. If we

accept that the F conditions Iead to different proprioceptive feedback conditions then a similarity

in feedback conditions is accompanied by decreased error.

Figure 5 . Significant main effect for block for mean RMSE for the retentiodtransfer phase.

NON-FATIGUE TRANSFER FATIGUE TRANSFER

1 2 3 4 5 6 BLOCK

1 2 3 4 5 6 BLOCK

++ NF ACQ

-a- F ACQ

Figure 6 . Three-way interaction: Acquisition Phase x Transfer Condition x Block for mean RMSE.

NON-FATIGUE TRANSFER

1 2 3 4 5 6 BLOCK

FATIGUE TRANSFER

1 2 3 4 5 6 BLOCK

Figure 7. Mean Tau (msec.) three-way interaction: Group x Transfer Condition x Block, for retentiodtransfer phase.

+ ACQ NF ACQ F

NF F

TRANSFER CONDITION

-O- ACQ NF

-a- ACQ F

Figure 8. Variability measure for Tau (msec), two way interaction: Group x Transfer Condition, for retentiodtransfer phase in Experirnent 2.

For maximum cross correlation there was a significant main effect for block, E(5, 160) =

9.69, p < -00 1, which renilted fkom the last block of acquisition @J = 1 -23 1) mering fiom aU the

retentionhransfer blocks (1 -63 7, 1.652, 1.688, 1-65 1). No other significant main effects or

interactions were revealed. The variability measure for maximum cross correlation yielded a main

effect for block, E(5, 160) = 4.265, p < -00 1, indicating that the £ k t block of retentiodtransfer

@I = 1 -394) was significantly dEerent fiom the last block of acquisition @f = 1.554) and ail

subsequent retentiodtransfer blocks (1 -6 17, 1.639, 1.692, 1.650). No other significant main

effects or interactions were revealed.

A main effect for block, E(5, 160) = 16.056, g < -000 1, was dso observed for the cross

correlation measure, revealing that subjects performed with less error during the first block of

retentiodtransfer (M = -937) than either the last block of acquisition (M = 1.224) or al1 other

subsequent retentionltransfer blocks (1 -273, 1 -270, 1.336, 1 -337). No other significant main

effects or interactions were exhibited. The variability measure for cross correlation revealed a

significant main effect for block, E(5, 160) = 18.94, p c .O00 1. The last block of acquisition a =

-1 17) proved to be less variable than the first block of retentiodtransfer (M =.276), with this latter

retentionltransfer block being more variable than ail subsequent retentiodtransfer blocks (. 134,

-1 3 7, -125, 0.87). Of greater interest is the significant two way interaction between group and

transfer condition, E(1, 32) = 6.72, g < -05, resulting fiom the NF-F condition performing with

more variability, than dl other conditions. More important is that the F-F and NF-M conditions

performed with less variability than either the F-NF or the NF-F condition (see Figure 9). No

other significant main effects or interactions were found.

NF F

TRANSFER CONDiTlON

+ ACQ NF

4 ACQ F

Figure 9. Standârd Deviation values for Cross Correlation, two-way interaction: Group x Transfer Condition, for retentionhransfer phase in Experiment 2.

Discussion

The primary objectives of Experiment 2 were to examine the effects of fatigue on a

relatively more complex motor task and to directly test the specincity of leaming hypothesis

(Proteau, 1992). Fatigue was used as means of impoverishing the proprioceptive feedback

associated with task performance. Thus, on the basis of the specificity of leaming hypothesis it

was predicted that subjects in the NF-NF and F-F conditions would perform better than those in

either the NF-F or F-NF conditions, as the former conditions maintained similar proprioceptive

feedback during acquisition and retention/transfer. However, with the latter conditions the

sensory feedback changed fiom acquisition to retentionltransfer, by either adding a richer source

of feedback or removing a source of previously available feedback. In many respects these

predictions were upheld.

For acquisition, the overall error measure (RMSE) indicated that at the end of acquisition

less error was observed for those participants who had greater practice regardless of fatigue

condition. The largest increase in performance occurred for al1 participants fiom blocks 1 to 2.

One possible explanation for this stems from a sirnilar study by Ivens (1996), in which a ceiling

efEect in performance was found to occur afler approximateiy 50 trials. While performance, in

this study, continued to improve across al1 trials, improvement later in practice was negligible in

cornparison to earlier performance measures. For retentiodtransfer, where an acquisition phase

by transfer condition by block interaction occurred, the effects clearly provide support for the

specificity of leaning hypothesis. Supeïior performance was revealed for those participants who

both acquired and performed the task dunng retentiodtransfer under similar conditions of fatigue

(NF-NF, F-F). Whereas a cost in performance occurred for participants who leamed and

performed the task under opposite (NF-F, F-NF) conditions of fatigue.

With regard to the other dependent measures examined, the measure of temporal error

revealed that upon transfemng to a NF condition al1 participants either displayed temporal lags or

leads in movement. However, when tramferring to a F condition, those participants who acquired

the task under a sirnilar condition approached a Tau of zero, indicating neither lags or leads, but

rather nearly perfectly timed movements. This provides support for the specificity of motor

Ieaming hypothesis and is elaborated upon in the General Discussion. Spatiaüy, the F-F condition

was less variable than either the F-NF or the NF-F condition, again suggesting that it may be best

to perform the task under conditions that allow for processing the type of feedback that was used

to develop a sensorimotor representation of the task during Ieaming. As weIl, ifyou have to

perform the task under different conditions, it appears best to transfer h m a F to a NF condition

rather than the reverse.

In summary, the results of Experiment 2 provide additional support for the specificity of

motor learning hypothesis, and extend the hypothesis (e.g., Elliott & Jaeger, 1988; Proteau et al.,

1992; Ivens, 1996) to include a manipulation other than visual feedback. Support was also found

for fatigue as a learning variable.

GENERAL DISCUSSION

The preceding experiments were pnmarily designed to assess the effects of fatigue on

learning. As wei!, they were designed to examine the appiicability of the specificity of leaming

hypothesis to the issue of fatigue and motor skiIl acquisition. Data from the first study provided

evidence to support the hypothesis that fatigue affects both the leaniing and the performance of a

motor skill. The second experiment provided additional support for the specificity of motor

learning hypothesis. It is assumed that the manipulation of fatigue had an effect on proprioceptive

feedback to the performer. Thus, the results herein served to provide new information regarding

the processes involved in human motor leaniing. The following sections relate the findings in the

present investigation to the existing body of literature.

Support for Fatigue as a Learning Variable

Consistent with Carron (1972), and Thomas et al. (1975) the present investigation

provides support for including fatigue as a leaming variable. Experiment 1 demonstrated that

acquiring the task under fatigue conditions compromised performance in the retentiodtransfer

phase. Initially, the position was put forth that discrepancies in the literature regarding whether

fatigue causes a leaming decrement, may be a consequence of rnethodoiogical differences in the

studies, including the type of task used, how fatigue was assessed and the fitness level of the

participant.

In the investigations by Carron (1 972) and Thomas et al. (19751, both of which found a

leaming decrement as a result of fatigue, a gross motor task was used both to fatigue the

participant as well as for testing. Of the three studies that have incorporated a gross motor task

to both induce fatigue and assess learning (Schmidt, 1969; Carron, 1972; Thomas et al., 1975),

two report a leaming eEect associated with fatigue (Carron, 1972; Thomas et al, 1975). Other

studies in which a learning effect has not been reported (Godwin & Schmidt, 1971; Spano &

Burke, 1976) have adopted either a combination of practice and test tasks (gross and single-limb),

or consistent single-lirnb conditions (Alderman, 1956). Taken together with the present

investigation in which a leaming effect was observed using a single-limb task for both fatigue and

testùig it seems unlikely that a simple explanation solely in terms of the type of task used is

tenable,

A potential alternative relates to the level of induced fatigue. As mentioned previously, it

is possible that only under relatively hi& levels of fatigue neuromuscular programrning changes

sufficiently enough to warrant a new motor program. Thus, in studies where no learning eEect

was revealed, it may be that the level of fatigue was not sufficient to change the relevant motor

program. For example, Schmidt (1969) had subjects cycle on a bicycle ergorneter for 2 minutes at

either easy or rnoderate levels of resistance to induce fatigue. Some authors (e.g., Dickinson,

Medhurst, & Whittingham, 1979) have suggested that moderate levels of exercise prior to

engaging in a task may facilitate a warm-up effect that can actually enhance rather than inhibit

performance. Thus, in studies where a learning effect was observed it rnay be that the

combination of heavy fatigue induced prior to task completion, and task similarity between

fatigue and test conditions is crucial (Carron, 1972; Thomas et al., 1975; Experiments 1 & 2

presented here).

Support for the Specificity of Motor Leamhg Hypothesis

Experiment 2 included sufficient conditions to determine the generalizability of the

specificity of learning hypothesis to the issue of fatigue and motor leaming. As outlùied earlier,

the hypothesis States that optimal performance on a task is directly related to the similarity

between the conditions under which a person learns and subsequently performs that task. Proteau

et al. (1987) sharpened the hypothesis to define specificity in terms of the sensory feedback

sources that are avaiiable to the performer during leamhg and performing of a skill. Proteau

argued that when the available sensory information changes (e-g., a person practises a skill with

visual feedback which is later rernoved when performing the task), performance deteriorates. A

similar performance decrement is aiso observed when sensory feedback is added to a condition in

which leaming originally occurred without such feedback (Proteau et al., 1992).

If indeed as suggested earlier, fatigue and non-fatigued conditions yield differect qualities

of proprioceptive feedback, acquiring a ski11 and developing a sensorimotor representation based

upon a particular type (or quality) of feedback will optirnize retention/transfer of that skill when

later performed with that feedback source available. For example, it is possible that fatigue

provides a degraded quality of aEerent feedback. During acquisition of a ski11 then, one would

learn to perfom the skiil and build a sensorimotor representation using this degraded feedback.

When the afferent feedback iniùdy relied upon changes (e-g., non-fatigue) task performance will

d e r . Thus, ifparticipants acquired a task under non-fatigue conditions and then completed the

cnterion task under fatigue conditions durhg retentiodtransfer, performance would deteriorate.

Indeed, in Experiment 2 reported here, specincity ofthe feedback sources available during the

leaming of a motor skill were crucial to task performance. When participants in Experiment 2

both leamed and performed the task under simiiar sensory feedback conditions @E-NF, F-F)

performance was superior. However, when the feedback conditions under which the task was

acquired were changed, task perfomance decreased. Thus, the present results provide further

support for the specificity of motor leaming hypothesis as proposed by Proteau and colleagues

(Proteau et al., 1987: Elliott & Jaeger, 1988; Proteau et al, 1992), and extend the hypothesis

beyond the visuaI feedback conditions that have been examined in previous studies.

In a larger theoreticai conte-, as suggested by Henry (1958), a memory store for motor

programs may exist for which a specific motor program and its appropriate neuromuscular

patterns is set up based on the available sensory information while leaming a movement (Willarns

et al., 1976). Perhaps, fatigue leads to a change in the recruitment pattern of the motor units

within a muscle, thus setting up a dEerent motor program as opposed to a non-fatigued state.

The data provided in these investigations also conform to Adams' closed-loop theory

(1971). Again, Adams hypothesized that a closed loop system for motor control exists, such that

afferent feedback available to the sensory receptors is integral in carrying out a movement. The

perceplual trace as posited by Adams is essentid in assessing a movement in progress. Intemal

(Serent) and extemal feedback sources are used to modify the movement until a perfect match

with the critenon is made. External feedback sources are used to strengthen the trace until the

individual no longer requires them to carry out the movement. Essential to Adams' theory is the

importance of afTerent feedback information. In the present study then, a degraded perceptual

trace resuiting fiom fatigue would serve as the primary source of af3erent information available to

the limbs while learning the movement. As long as this af5erent feedback remains constant, a

motor program would be set up based on this feedback. Thus, a person would l e m to perform a

movement in the presence of fatigue.

Some of the implications found regarding the arnount of feedback provided in the present

experiments indicate that ifsensory feedback in the form of fatigue is added prior to the leaming

of the task, more practice is required to learn the task. It is consistent with the above reasoning to

argue that if fatigue degrades the information at the sensorimotor level, then in order to

strengthen this afZerent information source, or in Adams' terms, strengthen the perceptual trace,

more practice trials are required. This was shown in Experiment 1, where participants in the

experimental condition took nearly twice as mmy trials as control subjects to reach a criterion

performance level. As well, in the second experiment, experimental participants in the higher

practice condition perfomed with less error than their lower practice counterparts.

Initially put forth as a theoretical alternative to Adams (1971), Schmidt (1975) offered a

schema theory of motor skill acquisition. Two aspects of scherna theory appear to be relevant to

the present discussion. First, Schmidt proposed the notion of a generalized motor program.

Inherent in this theory is the concept that as an individual leams a movement, a progression fiom

a closed to open-loop regdatory system arises. As a consequence, a relative independence fiom

the sensory feedback sources available d u ~ g acquisition occurs as learning progresses. Second,

schema theory includes the concept of variability of practice. Bnefly, variability of practice States

that varying the practice conditions under which a participant acquires a task will increase the

generalizability to other similar tasks. For example, training someone to complete a task at

varying speeds will yield positive transfer to novel versions of the task (unpractised). Schema

theory accounts for this phenornenon by predicting that Ieaming of the d e used to perforrn

different skills wiil be enhanced if the experiences that lead to rule development are varied as

opposed to constant practice during acquisition (Schmidt, 1988).

Schmidt's (1 975) conclusion that independence f h m feedback builds as leaming

progresses, is contradicted by the results of the present study. Rather, support here is for

dependence upon sensory feedback across leaming, and for the specificity of motor leaniing. If

the contrary had been the case, the addition or rernoval of sensory feedback during

retentiodtransfer conditions would not have afEected performance. One may wonder whether an

account based solely on the notion of practice variabiliq might account for the fmdings. If one

were to accept that fatigue inherently causes an increased amount of variability in task

performance, then it would foliow that acquiring the task under conditions of fatigue, should

transfer to either a fatigue or non-fatigue state equally well. However, this was not the case.

A more plausible and parsimonious explanation of the results is that fatigue and non-

fatigue acquisition conditions set up unique forms of proprioceptive information which serve as

the basis for developing sensorirnotor representations of the motor task. The idea that

consistency of feedback conditions in acquisition and subsequent retentionftransfer is the central

thesis of the specificity of learning hypothesis.

Although the issue of fatigue and motor learning has received relatively Iittle attention in

recent years, the present study suggests that the topic may warrant fùrther investigation. For

example, although Experiment 2 did not manipulate visual feedback, it would be interesting to

detemine how the two sources of sensory feedback afforded by manipulating fatigue and vision

might interact. Moreover, fürther examination into the impact of fatigue on gross as opposed to

single-limb motor skill acquisition is also warranted. Beyond the obvious theoreticai implications,

the present research rnay also lead to some practicai applications as well. Future research outside

the lab and into more "real world" settings could have impact on methods of training used in work

environments.

NOTES

Electrical activity from the nght ticeps brachaii (agonist) and biceps brachaii

(antagonist) muscles was measured with the use of Ag/AgCl surface electrodes (8 mm diameter).

A multichannel electromyographic @MG) system (mode1 544, Therapeutics Unlimited Inc.)

amplified the electrical signal corn the two sets of surface electrodes (maximum + 10v). The

EMG data were sampled at a rate of 1000 Hz. The s k i . at each electrode site was shaved, mbbed

with an abrasive pad (to remove the dead surface layer of sh), cleaned with a solution of 9 1%

isopropyl alcohol, and rubbed with electrode gel (Ingrarn & Bell Medical, Cardio-Cream) to

reduce skin irnpedance. Each electrode was fïlled with electrode gel and then anached to the skin

with a double sided adhesive tape (Converters, Inc., MET-250). To assist in the correct

placement of the electrodes, subjects were asked to contract their biceps and triceps muscles. The

electrodes were then aligned longitudinally with the direction of the muscle fibers and the

electrode wires were taped to the skin to prevent any puII on the electrodes.

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Bamett, M. L., Rodd, D., Schmidt, R. A., & Todd, B. (1973). Motor skills ieaming and the specificity of training principle. Research Ouarteriv, 44, 440-447.

Basmajian, J. V. Muscles dive their function revealed bv electromvography. Baltimore: Williams and Wilkins (1962).

Bawa, P., Sogaard, K., and Walsh, M- (1997). An examination of recruitment/ derecrument of hurnan motor units. Abstracts of the X X X m International Conrrress of Physiolomcd Sciences (Serial No. P078.12).

Carron, A V. (1972). Motor performance and learning under physical fatigue. Medicine and Science in Sports, 4, 10 1-106.

Dickinson, J., Medhurst, C., & Wittingham, N. (1979). W m - u p and fatigue in ski11 acquisition and performance. Journal of Motor Behavior, îJ 8 1-86.

Elliott, D., & Jaeger, M. (1988). Practice and the visual control of manual aiming movements. Journal of Human Movement studies, 24.279-29 1.

Fleury, M. & Bard, C. (1 987). effects of different types of physical activity on the performance of perceptual tasks in peripheral and central vision and coincident timing. Ergonornics, 30, 945-958.

Fox, E., Bowers, R., & Foss, M. The physiological basis for exercise and sport Indiana: Brown & Benchmark (1993).

Godwin, M. A., & Schmidt, R A (1971). Muscdar fatigue and discrete motor learning. Research Ouarterly, 42, 3 74-3 83.

Henry, F. M. "Specificity vs. Generality in Leamhg Motor Skills." Colleee Ph~sical Education Association Proceedings Washington, D. C. : Association, 195 8.

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Magill, R A. (1993). Motor leamine concepts and applications; fourth edition. Indiana: Wm. C. Brown Communications, Inc.

Proteau, L., Marteniuk, R G., Girouard, Y., & Dugas, C. (1 987). On the type of information used to control and learn an aiming movement after moderate and extensive training. Human Movement Science, 6- 18 1-199.

Proteau, L., Marteniuk, R G. & Levesgue, L. (1992). A sensorimotor basis for motor learning: evidence indicating specifïcity of practice. The Quarterlv Journal of Experimental PsychoIogy, 44. 3 557-575.

Romanow, S. K. E. Kinematic and perceptual analyses of the learning of complex movement sequences (Ph. D., Dissertation, simon Fraser University, 1934).

Schmidt, R k (1969). Performance and learning a gross motor ski11 under conditions of artificially-induced fatigue. Research OuarterIy, 40. 185- 190.

Schmidt, R. A. (1 975). A schema theory of discrete motor SHI leaming. Ps~chological Review, 82, 225-260.

Schmidt, R A. Motor Control and Leaminq- Champaign, DL: Human Kinetics Publishers, Inc. (1988).

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Thomas, J. R-, Cotten, D. J., Spieth, W. R, & Abraham, N. L. (1975). Effects of fatigue on stabilometer performance and leaming of males and fernales. Medicine and Science in Sports, 7.203-206. -

Wardlow, A Contemporaw nutrition-issues and insiehts. New York: Times Mosby (1 994).

Williams, L. Ii. T., Daniell-Smith, J. H. & Gunson, L. K. (1976). Specincity of training for motor skill under physical fatigue. Medicine and Science in Sport, 8, 162-167.

Table 2a

Cross Correlation

Note. Column one represents fatigue condition during acquisition (1 = non-fatigued, 2 = fatigued). Colurnn two represents trial group (1 = 100, 2 = 300).

Table 3a

Note. Column one represents fatigue condition during acquisition (1 = non-fatigued, 2 = fatigued). Column two represents trial group (1 = i00,2 = 300).

Table 4a

Note. Column one represents fatigue condition during acquisition (1 = non-fatigued, 2 = fatigued). Column two represents tnal group (1 = 100, 2 = 300).

RMSE

1 1 1 1 4.256201 1 4.1 598 1 4.1 794841 4-1 743 1 4.1 87764 1 1 11 4.252881 4.136121 4.163267) 4.172941 4,171869 1 1 1 1 4.237479 1 4.31251 4.255671 1 4.20731 4.243282 1 1 1 ) 4.174881 1 / 1 1 4.156946

4.191 68 4.1 3003

11 1 / 4.1 9624 1 4.25379 11 1 1 4.285161 1 4.22058

4.160202[ 4.1 51741 4.16391 8 4.1 13391 1 4.14859 4.1 620821 4.1 9383 4.21 35981 4.1 888

4.206544 4.207781 4.200921

1 1 1 / 4.23531 1 ( 4.2365 1 4.21 71 4.2391 1 4.21 2368 1 1 1 / 4.0728441 4.20559 1 4.1 72521 ] 4-1 83971 4.1 87391 1 1 1 / 4.346163 1 4.20678 1 ! 21 4.1 81 36 ( 4.21 1781

4.1 96026 1 4.1 854 1 4.1 94343

1 1 2 4.1 84903 1 4.222083 1 / 2 11 2 1 1 2 1 1 2

4.1 76338 4.21 3859

4.201 529 4.1 71 285

4.1 73001 4.1 75435

4.2459921 4.222363 ( 4.29031 8 1 4,068903) 4.1 72844

11 21 4.126438 / 4.1 4443 1 ! 2 f 4.257552 1 4.258025 1 1 21 4.21 31581 4.185752

4.1 87546 4.1 99772

4.1 36987 4.1 83806

4.1 77451 4.222909 4.1661 38,

4.3099391 4.151405

4.165695 1 4.1 891 061 4.1 781 36

4.1 7447 1 4.169738 4.1 95958 f 4.230898 4.1 8201 5 1 4.1 79685

1 i 21 4.2131 2 1 1 / 4.2821 63 21 1 / 4.215144

4.19961 1 1 4.1 92566 1 4.200841 4.1 6905 4.2020521 4.21 0991

4-1575) 4.233; 4.22071 4.1762 4.2593 1 4.2651 42 1 4.248 / 4.242026 4.18951 4.191

2 1 1 / 4.234237 1 4.1 6829 [ 4.1 87625 4.1 96 1 4.1 71 271

4.1 749 1 4.1 991 48 2 1 1 1 4.161 1871 4.1531 4.1651291 4.18491 4.180086 2; 1 1 4.23901 4.2378 4.231 987 1 4.30057 1 4.264286

4.1286821 4.12071 4.1 O7901 4.1 85955 1 4-21 849 / 4.21 889 4.204948 t 4.21 03 f 4.200438

2 1 1 1 4.166093, 4.1436 2 1 1 1 4.1 76647. 2 1 1 1 4.1 76647

4.1 931 8 4.1 931

2! 1 1 4.070295 4.1 01 35 ( 4.1 30087 / 4.1 438 1 4.1 47254 2 1 1 1 4.1 18557 1 4.28696 1 4.27741 4.21 91 / 4.1 9207 2 1 2 / 4.1 02508 1 4.21 5007 1 4.1 51 3041 4.1 57203 2 1 21 4.1741471 4.2034141 4,1978041 4.169266 2 1 21 4.2521 55 1 4.2453 1 4.221 6221 4.1 89352

4.1 931 37 4.174111 4.1 8351 6

2 1 2 1 4.203874 / 4.203874 1 3.61 1 164 1 4.1 33886 1 3.62371 1 2 1 2 4.1 37799 / 4.1 31 701 1 4.088789 / 4.0094521 4.033652 2 1 2 4.232791 4.164521 4.2001 ) 4.26076 1 4.25761 2 1 2 / 4.1 65938 2 1 2

4.207583 / 4.1 7921 1 1 4.1 99423 1 4.2021 08 4.231 7

2 1 2 2 1 2

4.25494 ( 4.1 7854 4.24495 1 4.2631 05 4.1641 59 / 4.1 62681 1 4.1 55766 4.221 871 4.1 6396 j 4.1 71 48

4.1 66969 1 4.1 50483 4-1 47 2 j 4.1 41 38

Tabfe 5a

Maximum Cross Correlation Standard Deviation

Note. Colurnn one represents fatigue condition during acquisition (1 = non-fatigued, 2 = fatigued). Column two represents trial group (1 = 100,2 = 300).

Table 6a

Cross Correlation Standard Deviation

Note. Column one represents fatigue condition during acquisition (1 = non-fatigued, 2 = fatigued). Column two represents trial group (1 = 100,2 = 300).

Table 8a

RMSE Standard Deviation

Note. Column one represents fatigue condition during acquisition (1 = non-fatigued, 2 = fatigued). Column two represents trial group (1 = 100,2 = 300).

APPlENDIX B

Cell means for the Retentioflransfer Phase for Experiment 2

Table l b

Transfer bfaximurn Cross Correlation

1 / 1 i 1 ) 1 -665093 1 1.231 1 07 1 1 -61 4348 ( 1.247567 [ 1 -674926 1 1 -665093 11 11 1 1 2.226921 1 1 -4551 171 1.8087041 1.861 31 3 11 1 1 1 1 2.087244 1 1 .41 61 83 1 1 -361 757

2.01 2498 ( 1 -81 8614 1 -602874 1 -524623 1 -82061 8

1 1 11 1 1 1 1 f 1

1 .SOI 395 1 1.1 O1 955 / 1.41 3334 0.658854 1 0.7241 93 1 0.748746

1 -592947

11 1 1 21 1 -3561 62 1 t.561264 1 2.067521 1.91 3759

1.65839

2.025714 ( 1 -645952

1 -761 767 0.775299 0.757497 1 0.849484

1 1 1 1 21 1 -222874 1 1 -685721 1 1 -788061 11 1 1 21 1 -427728 1 1 11 2j 1 JO71 75 1 / 1 I 2) 1 -56921

1.633087 1 1 -721 139 / 1 -593603 1.633087 1 -885741 1 -76641 9

1.696738 1.4931 35

1 / 2 1 1 1 1 -880089 / 1 -890308 1 2.27532q 1 1 2 1 1 1 2.331 492 1 1 -883473 1 1 -802847 1 1 -473801

1 -800908 1 -801 877

1 -721 139 1 1.593603 1 -671 881 ' 2.0691 35

11 2 1 1 j 0.9546921 0.691586f 1.991 192

-- I.9627621.882342-

2.1 291 14 1 2.077288

1.6092141 1 -864591 1 -784968

1 -577433 1 ) 2 / 1 j 1.563589 1 1.688845 1 2.1 66812 1 1 2 1 1 1 2.087244 1 1 -935805 / 2.082î42

1.234571

1 -725573

1.603542 2.435989 1 1 -860229 1 -791 323 1 1 -92222î

1.56421 1 1 -82465

1 I 2 1 21 1.812646 1 / 2 1 21 1 -930825

1.9549161 1.6136661 1.708799 1 1.9446361 2.048521 2.2471 07 / 2.1 9289 1 2.226921 2.855264 1 2.672425

11 2 / 2 11 2 1 2 1 1 2 1 2

1 -670366 1 -243321

2 1 11 1 1 1 -477508 / 1 -574255 1 1.6951 1 -982909 2 1 1 1 1 1 1 -985656 1 1 -505292 1 1.552518 1 1 -851 638

1.703136 1 539879

1 -040791 1 -043585 1 1.39241 1 -780045 1 1 -1 87494 1 1.269271 1 -306551 1 0.51 41 86 ( 0.886982

2 1 1 1 1 1 1 -854843 1 1.691 201 1 2.1 53301 1 1 -91 2561 1 1 -893759 i 1 -77541 6

1 -1 48932 1 0.820791 1 -9295871 1.948467 1 -98841 7 1 1.43901 9

1 S82555 1 -301 466 1 .O68512

2 1 1 1 1 1 1 -296039 1 1 -1 40552 1 -653967 0.75936 2 1 1 / 1

1 -626071 / 1 -541 071 1.885741 0.71 5477 / 0.861 831 1 0.71 41 94 0.91 5791 1 0.84301 1 -409557 1 1 -31 2871 1 0.90681 5 2 1 11 2 1 -057487 1 0.808569, 1 -04003

2 ! 11 2 1 -674926 1 2.0991 09 1 2.1 095 1 2.379576 1 2.231 338 2.394629 2 / 1 ! 21 1 -547669 1 0.91 8738 1 1 -527524 1 1 -429675 / 1 -489866 1.572358 2 / 1 1 21 1 -771 742 1.1 97531 1 1 -540474

1 .41 61 83 1 .51 71 52 1 .952327 1 1 -974756

1 -492589 1 -325723

2 1 11 2 2.1 04278 1 2.090606 1.398375 / 1 -607569 2.0691 35 1 1 -634502 2 1 2

1.790374 1 -61 4348 1.621 904

2.1 991 01 1 1 -492043 [ 1 -930825 1

2 1 2 1.724478 2.1 32762

1 1.948467 2.292534

2 1 2 1 2

2.1 70739 2.005298 2 i 2 1 1 1 2.2801 82 1 1.800908 2.021 271

2 1 2 1 1 1 1 -1 691 52 1 1 -0851 47 1 1 -045371 1 -096394 2 1 2 1 1 2 1 2 1 2

1 -039777 1 1.1 39661 0.596424 / 0.34845 1 0.394578 0.9124371 1 .O15921 1 1.049212

2.307762 1 -951 61 1 2.1 04278 1 2.3051 92' 2.364957 1.41 0028

2.435989 A -473801

0.855631 0.949375

0.308421 1 0.8589 18

1 -457675 2 [ 2 1 21 1 -3281 64 2.3678471 2.52251 8

0.891229

1 -396074 1 1 547065

0.977082

2.3451 7 2 1 2 / 21 2.300091 2 1 2 1 2 1 0.964551 1 0.8641 7 1 0.701 786

1 -51 601 1 1 2.226921 0.895909 1 1 -27631 5 1 1 .O97502

Note. Column one represents fatigue condition during acquisition (1 = non-fatigued, 2 = fatigued). CoIumn two represents trial group (1 = 100, 2 = 300). Column three represents fatigue condition during retentiodtransfer (1 = non-fatigued, 2 = fatigued). Column four consists of the last block of trials from day 1.

56

Table 2b

Transfer Cross Correlation

Note. Column one represents fatigue condition during acquisition (1 = non-fatigued, 2 = fatigued). Column two represents triai group (1 = 100, 2 = 300). Colurnn three represents fatigue condition during retentionhînsfer (1 = non-fatigued, 2 = fatigued). Colurnn four consists of the Iast block of trials nom day 1.

Table 4b

Transfer RMSE

Note. Column one represents fatigue condition during acquisition (1 = non-fatigued, 2 = fatigued). Column two represents trial group (1 = 100,2 = 300). Column three represents fatigue condition during retentionhnsfer (1 = non-fatigued, 2 = fatigued). Column four consists of the last block of trials from day 1.

Table Sb

Transfer Maximum Cross Correlation Standard Deviation

Note. Column one represents fatigue condition during acquisition (1 = non-fatigued, 2 = fatigued). Column two represents trial group (1 = 100, 2 = 3 00). Column three represents fatigue condition during retentiodtransfer (l = non-fatigued, 2 = fatigued). Column four consists of the last block of trials fiom day 1.

Table 6b

Transfer Cross Correlation Standard Deviation

Note. Column one represents fatigue condition during acquisition (1 = non-fatigued, 2 = fatigued). Column two represents trial group (1 = 100, 2 = 300). Column three represents fatigue condition during retentiodtransfer (1 = non-fatigued, 2 = fatigued). Column four consists of the last block of trials fiom day 1.

Table 7b

Transfer Tau Standard Deviation

Note. Column one represents fatigue condition during acquisition (1 = non-fatigued, 2 = fatigued). Column two represents trial group (1 = 100, 2 = 300). Column three represents fatigue condition d u ~ g retention/transfer (1 = non-fatigued, 2 = fatigued). Column four consists of the last block of trials nom day 1.

Table 8b

Transfer RMSE Standard Deviation

Note. Column one represents fatigue condition dunng acquisition (1 = non-fatigued, 2 = fatigued). Column two represents trial group (1 = 100, 2 = 300). Column three represents fatigue condition during retention/transfer (1 = non-fatigued, 2 = fatigued). Colurnn four consists of the last block of trials from day 1.

Informed Consent Form for Experiment 1

Inforrned Consent Form for Motor Learning and Motor Control Research

Effects of Fatigue on Fine Motor Performance

P ~ c i p a l Investigator: Tracey Kerr (Graduate Student) Dr. John Dickinson Dept. of Kinesiology Simon Fraser University

29 1-4065

This research is concerned with the effects of artificially induced fatigue on fine motor control. It is designed to answer several questions that relate to how human subjects learn and perform continuous responses.

Prior to the experiment subjects will be randomly assigned to two groups, an experirnental and a control group. Ifyou have been assigned to the experimental group your will have specific muscle fatigue induced on your nght limb. This wiii occur via concurrent bicep curls and tricep extensions as demonstrated by the experimenter. This motion wiil be repeated until the limb is sufficiently fatigued, but without injury. Some delayed onset muscle soreness may result from this exercise, and usually is exhibited 24 to 48 hours post exercise.

During the experiment your arm will be strapped ont0 a manipulandum to help isolate movement patterns. You will be required to perform foream movements that involve movement between two targets. You will be required to perform the rnovement in a predetemiined arnount of time. M e r each trial you will be told if you completes the task too quickly or too slowly. At the end of the experiment you will receive 10 dollars.

The experiment is comprised of two testing sessions which will last approximately one hour or less. Your participation is voluntary and you have the nght to withdraw at any time from the experiment. Your identity as a subject in the experiment will remain confidentid in that no record will be maintained of your name and participation after the data have been collected. If you have any questions regarding the procedure or complaints please do not hesitate to talk to the investigator.

Results from this study will be available to al1 subjects upon the studies completion. If you have any concems regarding this experiment please contact Dr. Andy Hoffer: Director, School of Kinesiology at 29 1-3 14 1.

Consent: 1 have read the above comments and understand the explmation, and 1 volunteer to participate in this research which will help advance the area of motor leaming. 1 also acknowledge that 1 will receive a copy of this consent form.

Date: Subject: (signature)

Witness:

64

Informed Consent Form for Experiment 2

Informed Consent F o m for Motor Learning and Motor Control Research

Effects of Fatigue and Specificity on the Performance and Leaming of a Fine Motor Skill

Principal Investigator: Tracey Kerr (Graduate Student) Dr. Dan Weeks Dept. of Kinesiology Simon Fraser University 29 1-4065

This research is concemed with the effects of fatigue on fine motor control. It is designed to answer several questions that relate to how human subjects learn and perform continuous responses.

Prior to the experiment subjects will be randomly assigned to four groups, three experimental and one control group. Ifyou have been assigned to the expenmentai group your will have specific muscle fatigue induced on your right limb. This wil1 occur via concurrent bicep curls and tncep extensions (approximately 5 setdl0 reps each) using varying weight (5-201bs) depending on the individual subject. This motion will be repeated until the limb is saciently fatigued, but without injury. Some delayed onset muscle soreness may result fi-om this exercise, and usually is exhibited 24 to 48 hours post exercise.

Dunng the experirnent your arm will be strapped ont0 a lever :O help isolate movement patterns. You wïll be required to perforrn forearm extension and extension- flexion movements in order to replicate a criterion curve that is displayed on the screen in front of you. After each trial you will receive feedback about the trial.

The expenment is compnsed of two testing sessions which will last approximately one hour or less. Your participation is voluntary and you have the right to withdraw at any time from the experiment. Your identity as a subject in the experiment will remain confidentid in that no record will be maintained of your name and participation after the data have been collected. If you have any questions regarding the procedure or cornplaints please do not hesitate to talk to the investigator.

Results £tom this study d l be available to dl subjects upon the studies completion. Eyou have any concems regarding this experiment please contact Dr. Andy Hoffer: Director, School of Kinesiology at 29 1-3 14 1.

Consent: 1 have read the above comrnents and understand the explanation, and 1 volunteer to participate in this research which will help advance the area of motor leaming. 1 also acknowledge that 1 d l receive a copy of this consent forrn.

Date: Subject: (signature)

Witness:

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