This double-blind experiment examined the effects of a caffeinated sports drink during prolonged cycling in a warm environment. Sixteen highly trained cyclists completed 3 trials: placebo, carbohydrate-electrolyte sports drink (CES), and caffeinated sports drink (CES+CAF). Subjects cycled for 135 min, alternating between 60% and 75% VO2max every 15 min for the first 120 min, followed by a 15-min performance ride. Maximal voluntary (MVC) and electrically evoked contractile properties of the knee extensors were measured before and after cycling. Work completed during the performance ride was 15–23% greater for CES+CAF than for the other beverages. Ratings of perceived exertion were lower with CES+CAF than with placebo and CES. After cycling, the MVC strength loss was two-thirds less for CES+CAF than for the other beverages (5% vs. 15%). Data from the interpolated-twitch technique indicated that attenuated strength loss with CES+CAF was explained by reduced intrinsic muscle fatigue.
Cureton, Wingo, and Trilk are with the Dept. of Kinesiology, University of Georgia, Athens, GA 30602-6554. Warren is with the Div. of Physical Therapy, Georgia State University, Atlanta, GA 30302. Millard-Stafford is with the School of Applied Physiology, Georgia Institute of Technology, Atlanta, GA 30332. Buyckx is with the Beverage Institute for Health and Wellness, The Coca-Cola Company, Atlanta, GA 30301.