Lee E. Brown, EdD, CSCS,*D

California State University, Fullerton

THE EFFECT OF SHORT TERM THE EFFECT OF SHORT TERM ISOKINETIC TRAINING ISOKINETIC TRAINING

ON LIMB VELOCITYON LIMB VELOCITY

THE EFFECT OF SHORT TERM THE EFFECT OF SHORT TERM ISOKINETIC TRAINING ISOKINETIC TRAINING

ON LIMB VELOCITYON LIMB VELOCITY

PrefacePrefacePrefacePreface

• Acute performance gains are attributed to learning.

• Motor learning is a neural event demonstrated physically.

• Neural adaptation has been shown relative to force.

• Activation or rate coding are responsible.

IntroductionIntroductionIntroductionIntroduction

• Force is only a byproduct of acceleration.

• Acceleration is the key to velocity.

• Maximum velocity results in maximum energy or force.

• KEY is to maximize the rate of force development.

Sport PhysicsSport PhysicsSport PhysicsSport Physics

• Mass = quantity of matter a body contains.

• Weight = mass x accel. of gravity.• Velocity = rate of change in position.• Acceleration = rate of change in velocity.• Force = mass x acceleration.• Torque = force x lever arm.• Work = torque x distance.• Power = work/time.

ImplementsImplementsImplementsImplements

ObjectsObjectsObjectsObjects

LaunchingLaunchingLaunchingLaunching

MediumMediumMediumMedium

InertiaInertiaInertiaInertia

EnergyEnergyEnergyEnergy

• Kinetic Energy = ½ mass x v2

• 300 grain bullet (M = (300 gr)/[7000 gr/lb 32.2 ft/sec2] = 0.00133 lb sec2/ft )

• v of 10f/s (.5x0.00133x102) = 0.06ft/lbs

• v of 3000f/s (.5x0.00133x30002)=5958ft/lbs

MeasurementMeasurementMeasurementMeasurement

• Resultant implement velocity is derived from human movement.

• Human movement is a function of neural and morphologic changes.

• Measurement of velocity is fundamental to performance.

• Isokinetics allows a window into human movement speed variability.

0

30

60

90

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150

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90 75 60 40 20 10

ROM (deg)

Velo

cit

y (

deg

/s)

DecelerationAcceleration

Load Range

(RVD)

(LR)

(DCC)

VariablesVariablesVariablesVariables

• RVD is sensitive to speed and human variability.

• LR is a function of ACCROM.

• Force is sensitive to speed and human variability.

• DCC is machine controlled.

0

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60 120 180 240 360 450

Velocity (deg/s)

RO

M (

de

g)

Load Range Accel. Decel.

Brown, L. E., Whitehurst, M., Gilbert, P.R. & Buchalter, D.N. (1995). The effect of velocity and gender on load range during knee extension and flexion exercise on an isokinetic device. J. Orthop. Sports Phys. Ther., 21(2), 107-112.

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Moritani, T. & deVries, H.A. (1979). Neural factors versus hypertrophy in the time course of muscle strength gain. American Journal of Physical Medicine, 58(3), 115-30.

Strength gains of untrained after initial 8-weeks are due to neural adaptation then muscular hypertrophy.

Trained

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20

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100

2 4 6 8

Weeks

% C

ontr

ibut

ion

Neural

Hypertrophy

Untrained

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120

2 4 6 8

Weeks

% C

ontr

ibut

ion

Neural

Hypertrophy

Prevost, M.C., Nelson, A.G., & Maraj, B.K.V. (1999). The effect of two days of velocity-specific isokinetic training on torque production. Journal of Strength and Conditioning Research, 13(1), 35-39.

Strength gains following short-term training utilizing isokinetic dynamometry are velocity specific (fast only) and related to neural adaptation. (~25% improvement)

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Torque

Pre-test

Post Test

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RationaleRationaleRationaleRationale

• Force is only a function of velocity.

• Max velocity is a function of acceleration.

• Therefore, training specificity should be reflected in acceleration and any force increase should be reflected in a concomitant increase in acceleration.

HypothesesHypothesesHypothesesHypotheses

• The fast training group will decrease RVD at the fast speed only.

• The slow group will exhibit no RVD change at any speed.

• The slow group will increase force at the slow speed only.

• The control group will exhibit no change at any speed.

Testing and Training DesignTesting and Training DesignTesting and Training DesignTesting and Training Design

• 60 college age male and female subjects.• Three random groups (control, fast and

slow).• Five maximal repetitions at 60 and 240

d/s.• Test on day one and day seven.• Two training sessions separated by 48

hours consisting of 3 sets of 8 repetitions at 60 or 240 d/s.

• Diverted the signal to an A/D board sampling at 1000Hz.

• Raw ASCII data exported to Excel as time, force, velocity and position columns.

• Three univariate (RVD, LR, & Force ) four-way mixed factorial (2 speeds X 2 times X 2 genders X 3 groups ) ANOVA’s to analyze the data.

Data Collection and AnalysisData Collection and AnalysisData Collection and AnalysisData Collection and Analysis

  CV r ICC SEM%

Error

RVD 13.15 .27 .40 .11 9.64

LR .49 .40 .58* .23 .30

DCCROM 16.37 .42 .59 .10 11.23

Force 22.18 .89* .94* 6.45 5.42

Reliability at 60 d/sReliability at 60 d/sReliability at 60 d/sReliability at 60 d/s

  CV r ICC SEM%

Error

RVD 9.00 .77* .87* .43 3.19

LR 3.43 .71* .83* .57 1.40

DCCROM 1.60 .37* .55* .23 1.05

Force 29.72 .95* .97* 3.99 5.13

Reliability at 240 d/sReliability at 240 d/sReliability at 240 d/sReliability at 240 d/s

• Significantly high variable reliability at fast speeds but not slow.

ResultsResultsResultsResults

• First study to evaluate velocity reliability.• Reliability of force consistent with:

– Farrell, 1986– Brown, 1992 & 1993

• Mean values consistent with:– Farrell, 1986– Taylor, 1991– Brown, 1992 & 1993– Wilson, 1997– Greenblatt, 1997

ReliabilityReliabilityReliabilityReliability

0

0.5

1

Control Slow Fast

RO

M (

deg

s)

Pre Post

DCCROM at 60 d/sDCCROM at 60 d/sDCCROM at 60 d/sDCCROM at 60 d/s

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25

Control Slow Fast

RO

M (

deg

s)

Pre Post

DCCROM at 240 d/sDCCROM at 240 d/sDCCROM at 240 d/sDCCROM at 240 d/s

Force at 60 d/sForce at 60 d/sForce at 60 d/sForce at 60 d/s

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125

Control Slow Fast

FO

RC

E (

lbs)

Pre Post

Force at 240 d/sForce at 240 d/sForce at 240 d/sForce at 240 d/s

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60

75

90

Control Slow Fast

FO

RC

E (

lbs)

Pre Post

• No significant differences in force or DCCROM by time for any group.

ResultsResultsResultsResults

• Force inconsistent with Prevost, 1999.

• Probably due to data reduction techniques.

• DCCROM consistent with:

– Farrell, 1986

– Taylor, 1991

– Brown, 1995

Force and DecelerationForce and DecelerationForce and DecelerationForce and Deceleration

RVD at 60 d/sRVD at 60 d/sRVD at 60 d/sRVD at 60 d/s

1

1.1

1.2

1.3

Pre Post

RO

M (

deg

)

Control Slow Fast

LR at 60 d/sLR at 60 d/sLR at 60 d/sLR at 60 d/s

74.5

74.75

75

75.25

75.5

Pre Post

RO

M (

deg

)

Control Slow Fast

RVD at 240 d/sRVD at 240 d/sRVD at 240 d/sRVD at 240 d/s

13

13.5

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14.5

Pre Post

RO

M (

deg

)

Control Slow Fast

LR at 240 d/sLR at 240 d/sLR at 240 d/sLR at 240 d/s

39.5

40

40.5

41

Pre Post

RO

M (

deg

)

Control Slow Fast

• Significant decrease in RVD by time for the slow group at the slow speed and for the fast group at the fast speed.

• Significant increase in LR by time for the slow group at the slow speed and for the fast group at the fast speed.

ResultsResultsResultsResults

• Reduction in RVD results in LR increase.

• Reduction of RVD with maintenance of force results in an increase in rate of force development.

Acceleration and Load RangeAcceleration and Load RangeAcceleration and Load RangeAcceleration and Load Range

ConclusionsConclusionsConclusionsConclusions

• Acute improvements may be explained as the result of neural adaptations.

• Increased motor unit recruitment or firing rate.

• Increased rate of force development may maximize human performance.

• Future research should determine optimum frequency and volume for velocity specific training.

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• Chapter 6

• Abstract homework