Short-term High Fat Diet Prior Short-term High Fat Diet Prior to Carbohydrate Loading: to Carbohydrate Loading: Gender Differences on Gender Differences on Perceived Performance and Perceived Performance and Time to Fatigue Time to Fatigue

Alaine MillsKINS 6130November 16, 2010

Introduction Introduction Fuel Sources during Endurance

Exercise◦Carbohydrates and Fats

Most important to ensure optimal performance

◦Protein Plays a small energetic role during

endurance activities

The Importance of The Importance of Carbohydrates for Endurance Carbohydrates for Endurance AthletesAthletesPlay a role in the rapid metabolizing of

fats for energyIf liver & muscles are depleted of

glycogen, athlete will experience extreme fatigue ◦“Hitting the wall”

Carbohydrate stores are limited◦ Needs increase for endurance exercise(Sedlock, 2008)

The Importance of The Importance of Carbohydrates for Endurance Carbohydrates for Endurance AthletesAthletesThe CNS relies on carbohydrates

to function properly◦Mental fatigue

The time to exhaustion during endurance◦directly related to the initial levels of

stored muscle glycogen(Sedlock, 2008)

The Importance of Fats for The Importance of Fats for Endurance Athletes Endurance Athletes Fat becomes a primary source of

energyEndurance training improves the

body's ability to utilize fats for energy◦Able to mobilize fats from adipocytes

making more fatty acids available to working muscle

Endurance training also improves the working muscle’s capacity to oxidize fats that are delivered

(Sedlock, 2008)

Carbohydrate Loading Carbohydrate Loading Manipulating one’s diet to

enhance performance◦High carbohydrate diet several days

prior to competition

Maximizing muscle glycogen levels before an exercise event to help prevent fatigue (Sedlock, 2008)

Literature ReviewLiterature ReviewResearch on short term high fat

diets prior to CHO loading (Lambert, 2001; Havemann, 2006; Burke, 2000)

Results:◦Modified patterns of fuel substrate

utilization◦Enhanced subsequent exercise capacity ◦Maximized the capacity for fat oxidation

Increased reliance on fat Decreased reliance on muscle glycogen

Literature ReviewLiterature Review

Women oxidize more lipids during exercise than men (Tarnopolsky, 1993; Devries, 2006).

◦ Lower RER◦ Greater Reliance on fat oxidation ◦ Due to Estrogen?

Some studies done on carbohydrate loading showed no effects on women (Tarnopolsky, 2001).

Literature ReviewLiterature Review

Gaps in Previous Research on High Fat Diets: ◦Primarily male subjects only (Lambert,

2001; Havemann, 2006; Burke, 2000)

◦Lack of female-male comparison◦Primarily Cycling (Lambert, 1994; Goedecke,

1999; Van Zyl, 1996)

PurposePurposeTherefore, the purpose of this

study is to compare male and female endurance runners on perceived performance and time to fatigue after following a short-term high fat diet prior to carbohydrate loading.

Research Hypotheses Research Hypotheses Women will increase their time to

fatigue significantly more than men.

Women will decrease their RPE score significantly more than men.

LimitationsLimitationsConvenience Sampling

◦Volunteers No randomization Internal & External Validity

DelimitationsDelimitationsOnly endurance runnersOne age groupOnly one type of diet will be

analyzed

AssumptionsAssumptionsParticipants will not deviate from

the assigned diet planParticipants will give maximal

effort throughout the study

Participants Participants Convenience Sample

◦20 volunteers who run 3 days per week Average 30 minutes per session

◦Ages: 19-24 years old College students

◦Grouped according to gender◦Recruitment ◦Informed consent

Preliminary TestingPreliminary Testing◦Anthropometric Data

Height & Weight

◦Body Fat Percentage BIA

Reliable (r= 0.95-0.987) Criterion-Related Validity(Jackson,1988)

Preliminary Testing Preliminary Testing VO² Max Test

Modified Bruce Treadmill TestProvides warm-upTreadmill speed increases in speed and

grade every 3 minutes. Stage Speed (mph) Grade (%) Duration (min)

0 1.7 0 3

.50 1.7 5 3

1 1.7 10 3

2 2.5 12 3

3 3.4 14 3

4 4.2 16 3

5 5.0 18 3

6 5.5 20 3

7 6.0 22 3

Preliminary TestingPreliminary TestingBruce Treadmill Test

◦Stability Reliability r=0.96

◦Criterion-Related Validity Expected relationships verified

(Robinson,2001)

Gender and Age Equation Activity Factor

18-30 year old Males (15.3 X BW) + 679 1.6-2.4

18-30 year old Females (14.7 X BW) + 496 1.6-2.4

RestingResting EnergyEnergy ExpenditureExpenditure CalculationsCalculations andand ActivityActivity FactorsFactors

BW = Body Weight in Kg World Health Organization, 2010

Dietary ManipulationsDietary Manipulations

NHANES Food Frequency Questionnaire

Dietary ManipulationsDietary Manipulations

7 days 3-days

(Lambert,2001) (Havemann,2005)

Performance Performance MeasurementMeasurementTime to Exhaustion

◦ Treadmill run to exhaustion @70% VO²max◦ Time to Exhaustion : The point when the subject can no longer

maintain exercise intensity For 15 seconds

◦ Reliability “Finding that there was no significant difference between

trials enables future researchers to utilize the Robinson protocol with confidence that the trials will consistently be the same.” (Robinson, 2001)

◦ Face Validity

(Walsh, 2010)

Performance Performance MeasurementMeasurementRate of Perceived

Exertion◦ Validated Borg RPE

Scale Criterion-Related

Validity Correlation w/ HR

Reliable (r=0.86) (Chen, 2002)

◦ An ordinal scale◦ Verbally Explained◦ The greater the exertion

felt the greater the number reported by the individual being tested

ProcedureProcedureTrial 1

◦Prior to any dietary manipulations◦Standard Warm-up◦Timed run to Exhaustion ◦Evaluation of RPE every 3 minutes

ProcedureProcedureDiets Begin

◦High Fat Diet for 7 days◦Carbohydrate Loading for 3 days

following the High Fat Diet Trial Two

◦Day 11◦Performed the same way as trial 1

Statistical AnalysisStatistical AnalysisTwo way ANOVA with Repeated Measures

◦ Independent Variable: Gender (Male and Female)

◦ Dependant Variable Time to Exhaustion (Pre and Post)

Two way ANOVA with Repeated Measures◦ Independent Variable: Gender (Male and

Female)◦ Dependant Variable

RPE (Pre and Post)

α < .05

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