Salbutamol effects on systemic potassium dynamics during and following intense continuous and intermittent exercise.

Abstract

Salbutamol inhalation is permissible by WADA in athletic competition for asthma management and affects potassium regulation, which is vital for muscle function. Salbutamol effects on arterial potassium concentration ([K+]a) during and after high-intensity continuous exercise (HIcont) and intermittent exercise comprising repeated, brief sprints (HIint), and on performance during HIint are unknown and were investigated. Seven recreationally active men participated in a double-blind, randomised, cross-over design, inhaling 1000µg salbutamol or placebo. Participants cycled continuously for 5min at 40% [Formula: see text]O2peak and 60% [Formula: see text]O2peak, then HIcont (90s at 130% [Formula: see text]O2peak), 20min recovery, and then HIint (3 sets, 5×4s sprints), with 30min recovery. Plasma [K+]a increased throughout exercise and subsequently declined below baseline (P<0.001). Plasma [K+]a was greater during HIcont than HIint (P<0.001, HIcont 5.94±0.65 vs HIint set 1, 4.71±0.40mM); the change in [K+]a from baseline (Δ[K+]a) was 2.6-fold greater during HIcont than HIint (P<0.001). The Δ[K+] throughout the trial was less with salbutamol than placebo (P<0.001, treatment main effect, 0.03±0.67 vs 0.22±0.69mM, respectively); and remained less after correction for fluid shifts (P<0.001). The Δ[K+] during HIcont was less after salbutamol (P<0.05), but not during HIint. Blood lactate, plasma pH, and the work output during HIint did not differ between trials. Inhaled salbutamol modulated the [K+]a rise across the trial, comprising intense continuous and intermittent exercise and recovery, lowering Δ[K+] during HIcont. The limited [K+]a changes during HIint suggest that salbutamol is unlikely to influence systemic [K+] during periods of intense effort in intermittent sports.