Can caffeine supplementation reverse the negative effect of the time of the day during a repeated sprint ability test?

Abstract

The objective of this study is to investigate the effects of caffeine ingestion (5 mg.kg-1) on performance during a repeated sprint ability (RSA) test performed during different periods of day. Fifteen participants will take part in this study. All participants will attend the laboratory to perform six tests: 1) one incremental test and two RSA test familiarization conditions (The RSA test is constituted by ten 6-s cycle sprints, with 24 s of rest between them); 2) two RSA tests, one in the morning with placebo (Morning-PLA) and one in the morning with caffeine (Morning-CAF); 3) two tests in the evening, one with placebo ingestion (Evening-PLA) and another with caffeine ingestion (Evening-CAF). During all tests VO2, VCO2, e VE and HR will be measured. Peak power output (PPO), mean power output (MPO), and anaerobic power reserve (APR) will be calculated for each maximal 6-s cycling bout. Furthermore, the fatigue index for PPO and MPO will be calculated. Finally, before and after each sprint the rating of perceived exertion, adrenaline and noradrenaline and lactate concentrations will be measured. A two-way (condition and time of day) analysis of variance with repeated measurements in the second factor will be used to compare groups and conditions. The effect size will be calculated via eta squared. (AU)