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

Abstract

Purpose

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 (HI_cont) and intermittent exercise comprising repeated, brief sprints (HI_int), and on performance during HI_int are unknown and were investigated.

Methods

Seven recreationally active men participated in a double-blind, randomised, cross-over design, inhaling 1000 µg salbutamol or placebo. Participants cycled continuously for 5 min at 40 % \( {\dot{\text{V}}} \) O_2peak and 60 % \( {\dot{\text{V}}} \) O_2peak, then HI_cont (90 s at 130 % \( {\dot{\text{V}}} \) O_2peak), 20 min recovery, and then HI_int (3 sets, 5 × 4 s sprints), with 30 min recovery.

Results

Plasma [K⁺]_a increased throughout exercise and subsequently declined below baseline (P < 0.001). Plasma [K⁺]_a was greater during HI_cont than HI_int (P < 0.001, HI_cont 5.94 ± 0.65 vs HI_int set 1, 4.71 ± 0.40 mM); the change in [K⁺]_a from baseline (Δ[K⁺]_a) was 2.6-fold greater during HI_cont than HI_int (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 ± 0.69 mM, respectively); and remained less after correction for fluid shifts (P < 0.001). The Δ[K⁺] during HI_cont was less after salbutamol (P < 0.05), but not during HI_int. Blood lactate, plasma pH, and the work output during HI_int did not differ between trials.

Conclusions

Inhaled salbutamol modulated the [K⁺]_a rise across the trial, comprising intense continuous and intermittent exercise and recovery, lowering Δ[K⁺] during HI_cont. The limited [K⁺]_a changes during HI_int suggest that salbutamol is unlikely to influence systemic [K⁺] during periods of intense effort in intermittent sports.

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