Effect of Various Carbohydrate-Electrolyte Fluids on Cycling Performance and Maximal Voluntary Contraction

The purpose of this study was to compare the effects of a carbohydrate-electrolyte plus caffeine, carnitine, taurine, and B vitamins solution (CE+) and a carbohydrate-electrolyte-only solution (CE) vs. a placebo solution (PLA) on cycling performance and maximal voluntary contraction (MVC). In a randomized, double-blind, crossover, repeated-measures design, 14 male cyclists (M +/- SD age 27 +/- 6 yr, VO2max 60.4 +/- 6.8 ml.kg(-1) . min(-1)) cycled for 120 min submaximally (alternating 61% +/- 5% and 75% +/- 5% VO2max) and then completed a 15-min performance trial (PT). Participants ingested CE+, CE, or PLA before (6 ml/kg) and every 15 min during exercise (3 ml/kg). MVC was measured as a single-leg isometric extension (70 degrees knee flexion) before (pre) and after (post) exercise. Rating of perceived exertion (RPE) was measured throughout. Total work accumulated (KJ) during PT was greater (p < .05) in CE+ (233 +/- 34) than PLA (205 +/- 52) but not in CE (225 +/- 39) vs. PLA. MVC (N) declined (p < .001) from pre to post in PLA (988 +/- 213 to 851 +/- 191) and CE (970 +/- 172 to 870 +/- 163) but not in CE+ (953 +/- 171 to 904 +/- 208). At Minutes 60, 90, 105, and 120 RPE was lower in CE+ (14 +/- 2, 14 +/- 2, 12 +/- 1, 15 +/- 2) than in PLA (14 +/- 2, 15 +/- 2, 14 +/- 2, 16 +/- 2; p < .001). CE+ resulted in greater total work than PLA. CE+, but not PLA or CE, attenuated pre-to-post MVC declines. Performance increases during CE+ may have been influenced by lower RPE and greater preservation of leg strength during exercise in part as a result of the hypothesized effects of CE+ on the central nervous system and skeletal muscle.