The effect of induced alkalosis and submaximal cycling on neuromuscular response during sustained isometric contraction

Abstract

The aim of this study was to determine if inducing metabolic alkalosis would alter neuromuscular control after 50 min of standardized submaximal cycling. Eight trained male cyclists (mean age 32 years, s¼7; _V O2max 62 ml kg71 min71, s¼8) ingested capsules containing either CaCO3 (placebo) or NaHCO3 (0.3 g kg71 body mass) in eight doses over 2 h on two separate occasions, commencing 3 h before exercise. Participants performed three maximal isometric voluntary contractions (MVC) of the knee extensors while determining the central activation ratio by superimposing electrical stimulation both preingestion and post-exercise, followed by a 50-s sustained maximal contraction in which force, EMG amplitude, and muscle fibre conduction velocity were assessed. Plasma pH, blood base excess, and plasma HCO3 were higher (P50.01) during the NaHCO3 trial. After cycling, muscle fibre conduction velocity was higher (P50.05) during the 50-s sustained maximal contraction with NaHCO3 than with placebo (5.1 m s71, s¼0.4 vs. 4.2 m s71, s¼0.4) while the EMG amplitude remained the same. Force decline rate was less (P50.05) during alkalosis-sustained maximal contraction and no differences were shown in central activation ratio. These data indicate that induced metabolic alkalosis can increase muscle fibre conduction velocity following prolonged submaximal cycling.