David Gray Lassiter

Supervisor: Dr. John L. Ivy

Energy drink consumption before exercise enhances

exercise performance (Ivy, 2009)

Energy drink consumption improves reaction time at rest (Howard & Marczinski, 2010)

Caffeine and carbohydrate consumption during exhaustive exercise improves information processing (Hogervorst, 2008)

Will energy drink consumption prior to shorter duration exercise improve performance on cognitive tests during and after exercise?

Background

Consumption of an energy drink will

1. Improve cycling performance on a 35-km time trial

2. Improved cognitive and psychomotor performance

A. At rest

B. After a time trial while still exercising at 70% of VO2MAX

C. After a time trial during cool down

Hypotheses

Design

Baseline mental acuity tests (Pre Drink, Pre Race)

Energy drink (ED) or placebo (PLA) consumption

After 40 minutes, more mental acuity tests (Post Drink, Pre Race)

35-km time trial

Expired gasses collected during time trial

After time trial, final mental acuity tests (Post Race)

Blood drawn throughout visit

Randomized crossover

Protocol

Dependent Variables

Exercise Measures

Time trial performance

Perceived exertion (RPE)

Cognitive/Psychomotor Measures

Decision making accuracy and speed

Psychomotor accuracy and speed

Physiological Measures

Heart rate

Respiratory

Blood analytes

Women VO2max ≥ 45 mL/kg/min

Men VO2max ≥ 55 mL/kg/min

Participants

Ingredients in the Energy Drink

2 servings distributed

-Includes 160 mg of caffeine and 54 g of carbohydrates in total

Statistical Analysis

Repeated measures ANOVA (Time*Treatment)

Greenhouse-Geisser correction was made when Mauchly’s W<.05

LSD for post-hoc analyses

α=.05

Results

Results- Differing Baseline Blood Caffeine Concentrations

Statistical Analysis Revisited

Categorized participants into 2 groups:

HI: baseline blood caffeine > 1000 ng/mL at both visits (N=5)

LO: everyone else (N=10)

Performed a 3-way ANOVA (Time*Treatment*Category)

Time and Treatment were WS factors

Category was BS factor

3-way ANOVA did not change any interpretations

Results- ED Enhanced Race Performance

Results- ED Led to Uncoupling of RPE from Exertion

Results- ED Increased VO2 Without Increasing RER

Results- ED Reduced Concentration of Substrates

Results- ED Increased Movement Speed on Simple Test Only

Results- Exercise Enhanced Reaction Time

Results- ED Negligibly Diminished Precision

Conclusions

This ED will enhance aerobic performance if taken before

exercise

Effect is regardless of baseline blood caffeine concentrations

Likely due to non-caffeine ingredients

At least 225 mg of caffeine must be taken with carbohydrate to enhance exercise performance greater than carbohydrate alone (Kovacs, 1998)

Studies utilizing controls in addition to PLA are recommended to elucidate the differential contributions of ingredients in this ED

Exercise Performance

This ED may enhance simple movement speed when

an athlete does not have to multi-task

This ED likely has no effects on reaction time, precision, or decision making (not shown)

Future studies ought to use whole-body reaction time to assess the ED’s effects since this is more ecologically relevant and caffeine alone has been shown to be effective (Duvnjak-Zaknich, 2011)

Cognitive and Psychomotor Performance