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

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 % V ˙ O _2peak and 60 % V ˙ O _2peak, then HI _cont (90 s at 130 % 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.