Prolonged Cycling Exercise Alters Neural Control Strategy, Irrespective of Carbohydrate Dose Ingested

Abstract

The interactions between CHO dosage and neuromuscular regulation following fatiguing endurance exercise are not well understood. Fifteen well‐trained male cyclists completed 4 experimental trials of 120‐min submaximal cycling (95% lactate threshold) during which water (0 g CHO·h−1) or CHO beverages (20, 39, or 64 g CHO·h−1) were consumed every 15 minutes, at a rate of 1 L·h−1, followed by a work‐matched time trial ~30 minutes. Maximal voluntary contraction (MVC), M‐wave twitch potentiation and torque, motor unit recruitment and firing rate were recorded pre‐ and post‐cycling. Time trial performance improved following 39 and 64 versus 0 and 20 g CHO·h−1, with no effect of CHO dose on any pre‐ to post‐neuromuscular function measures. Pre‐ to post‐cycling exercise: (1) MVC, and M‐wave amplitude and duration declined by −21.5 Nm, and −4.9 mV and −7.1 ms, respectively; (2) peak evoked torque remained unchanged; (3) Firing rate of early‐ and mid‐recruited motor units increased by 0.93 pps and 0.74 pps, respectively, with no change in later‐recruited motor units. Thus, central drive to early‐ and mid‐recruited motor units increases as a result of endurance cycling, due to a likely fatigue compensatory mechanism. However, CHO availability does not appear to influence increased neuromuscular drive.