Critique of an Article from the Journal of Applied Physiology

Critique of an article from the Journal of Applied Physiology

“Effect of different protocols of caffeine intake on metabolism and endurance performance”

By Steve Bradley, BUSN 670, Queens University

February 3rd, 2004

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 70% of VO2 peak was used for the rest of the trials. This compensated for varying levels of fitness among the athletes and corresponds to mid range workout. The subjects refrained from caffeine, standardized diet, and standardized training for 48 hrs before the trials. For 24 hours before the trials, each subject was given a prepackaged standard diet. Exercise and food diaries were kept and checked for compliance.

Each trial consisted of two hours of steady state cycling at 70% VO2 peak immediately followed by an all out time trial. Study A compared placebo (no caffeine), caffeine before the trial (precaf), during trial (durcaf),