Purpose: The purpose of the present study was to investigate the effect of high-dose inhaled terbutaline on muscle strength, maximal sprinting, and time-trial performance in trained men.
Methods: Nine non-asthmatic males with a VSO₂max of 58.9 ± 3.1 ml min(-1) kg(-1) (mean ± SEM) participated in a double-blinded randomized crossover study. After administration of inhaled terbutaline (30 × 0.5 mg) or placebo, subjects' maximal voluntary isometric contraction (MVC) of m.quadriceps was measured. After MVC, subjects performed a 30-s Wingate test. Sixty minutes following the Wingate test, subjects exercised for 10 min at 80% of VSO₂max and completed a 100-kcal time trial. Aerobic contribution was determined during the Wingate test by indirect calorimetry. Furthermore, plasma terbutaline, lactate, glucose, and K(+) were measured.
Results: Inhalation of 15 mg terbutaline resulted in systemic concentrations of terbutaline of 23.6 ± 1.1 ng ml(-1) 30 min after administration, and elevated plasma lactate (P = 0.001) and glucose (P = 0.007). MVC was higher for terbutaline than placebo (738 ± 64 vs. 681 ± 68 N) (P = 0.007). In addition, Wingate peak power and mean power were 2.2 ± 0.8 (P = 0.019) and 3.3 ± 1.0% (P = 0.009) higher for terbutaline than placebo. Net accumulation of plasma lactate was higher (P = 0.003) for terbutaline than placebo during the Wingate test, whereas [Formula: see text] above baseline was unchanged by terbutaline (P = 0.882). Time-trial performance was not different between treatments (P = 0.236).
Conclusion: High-dose inhaled terbutaline elicits a systemic response that enhances muscle strength and sprint performance. High-dose terbutaline should therefore continue to be restricted in competitive sport.