The Effect of Carbohydrate Beverage Ingestion on Central versus Peripheral Fatigue: A Placebo-Controlled, Randomized Trial in Cyclists

Purpose: We investigated whether carbohydrate ingestion delays fatigue in endurance-trained cyclists via peripheral or central mechanisms. Methods: Ten men [35±9 yrs] and ten women [42±7 yrs] were assigned, in a double-blind, cross-over design to a sports drink [CHO] and placebo [PL]. Strength measures were made 3 times [pre-exercise, post-time trial and post-ride to exhaustion]: 1) Maximal voluntary contraction [MVC]; 2) MVC with superimposed femoral nerve magnetic stimulation to measure central activation ratio [CAR]; 3) femoral nerve stimulation in a 3-second pulse train on relaxed muscle. Subjects cycled 2 hours at ~65% of peak oxygen consumption [VO2peak], with 5 1-minute sprints interspersed, followed by a 3-km time trial. After strength testing, cyclists remounted their bikes, performed a brief warmup, and pedaled at ~85% VO2peak until unable to maintain workload. Changes in metabolic and strength measurements were analyzed with repeated measures ANOVA. Results: From pre-exercise to post-time trial: MVC declined in men (17%) and women (18%) [p=0.004] with no effect of beverage [p>0.193]; CAR decreased in both sexes with PL [P=0.009], the decline was attenuated by CHO in men only [time×treatment, p=0.022]; there was no evidence of peripheral fatigue in either sex with either beverage [p>0.122]. Men rode faster in the time trial with CHO [p=0.005] but did not improve performance in the ride to exhaustion [p=0.080]. In women, CHO did not improve performance in the time trial [p=0.173], or in the ride to exhaustion [p=0.930]. Conclusion: Carbohydrate ingestion preserved central activation and performance in men, but not women, during long-duration cycling.The accepted manuscript in pdf format is listed with the files at the bottom of this page. The presentation of the authors' names and (or) special characters in the title of the manuscript may differ slightly between what is listed on this page and what is listed in the pdf file of the accepted manuscript; that in the pdf file of the accepted manuscript is what was submitted by the author