Critique of an article from the Journal of Applied Physiology

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Critique of an article from the Journal of Applied Physiology

"Effect of different protocols of caffeine intake on metabolism and endurance performance"

Introduction

In 2002, a group of Australian researchers published a paper entitled the "Effect of different protocols of caffeine intake on metabolism and endurance performance". Caffeine use during sporting events has become much more popular and has widely studied. The purpose of the research was to examine the work increasing (ergogenic) effects of differing regiments of caffeine on metabolism and performance while simulating the typical nutritional preparation an athlete would do for a race. The study also sought to examine the effect of timing of caffeine intake, comparing results when caffeine was given before an event (precaf) to results from caffeine given during an event (durcaf). In addition, the researchers wanted to understand the practice of endurance athletes drinking defizzed Coca-Cola towards the end of a race. It was widely observed that many triathletes and marathoners feel they derive a boost from consuming Coca-Cola in the final stages of an event as a replacement to sports drinks.

Participants and Overall Research Design

Two similar, but separate studies were conducted. The first study (A) used 12 highly trained athletes, either triathletes or cyclists. The second study (B) used a smaller sample of 8 athletes with similar backgrounds. While training histories were similar, caffeine intake histories varied from occasional to regular intake of up to ~150 mg/day (2mg/Kg). Subjects first performed a maximal incremental power test to determine their VO2 peak, a measurement of the body's ability to taken in O2 and turn it into work. A work rate of ...

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...e that negated some or all of the impact of the caffeine. 5) Test method variation (for blood or urinary tests) was not a factor. No data was given indicating the reproducibility of the test methods used.

A proposal to improve the design is examining the results versus pre-trial caffeine use. Would individuals who habitually use caffeine have the same performance enhancement as those who occasionally

use it or would the effect be lower? Another suggestion is to include a statement discussing test method variation and the impact (or lack of impact) on the test results. Finally, a larger sample size can help determine if borderline data is significant. While cost is almost always a consideration in research, the text discusses changes in muscle metabolism as not detectable. Additional data from more test subjects could produce results with statistical significance.

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