Effects of acute salbutamol inhalation on quadriceps force and fatigability

Introduction: Oral beta2-agonist administration improves muscle function in persons without asthma. We performed a double-blind, randomized, controlled crossover study to assess whether acute inhaled salbutamol administration improves muscle strength and fatigability in healthy moderately trained subjects. Methods: Quadriceps muscle strength was measured during maximal voluntary contraction (MVC) and femoral nerve magnetic stimulation (potentiated single twitch, TwQ(peak)) before and after (i) a maximal incremental cycling test (n = 10) and (ii) 50 maximal isometric one-leg extensions (n = 9). Each exercise test was performed on three occasions, after salbutamol (200 and 800 mu g) or placebo inhalation. Results: Before exercise, treatments had no significant effect on MVC [(placebo) 597 146 N vs (200 mu g) 629 151 N vs (800 mu g)610 +/- 148 N] and TwQ(peak) [(placebo) 215 +/- 83 N vs (200 mu g) 227 +/- 69 N vs (800 mu g) 250 +/- 84 N]. Maximal power during cycling and maximal force during leg extensions did not differ between treatments. Treatments had no effect on MVC and TwQ(peak) reductions at 30 min [MVC: (placebo) -8 +/- 9% vs (200 mu g) -9 +/- 7% vs (800 mu g) -8 +/- 5%; TwQ(peak): (placebo) -29 +/- 13% vs (200 mu g) -23 +/- 15% vs (800 mu g) -20 +/- 8%] and 60 min [MVC: (placebo) -12 +/- 17% vs (200 mu g) -6 +/- 9% vs (800 mu g) -8 +/- 8%; TWQ(peak): (placebo) -20 +/- 21% vs (200 mu g) -19 +/- 23% vs (800 mu g) -8 +/- 7%] after cycling. Similarly, reductions in MVC and TWQ(peak) were not significantly different between treatments at 30 [MVC: (placebo) -11 +/- 9% vs (200 mu g) -12 +/- 7% vs (800 mu g) -8 +/- 16%; TwQ(peak): (placebo) -37 +/- 12% vs (200 mu g) -33 +/- 20% vs (800 mu g) -32 +/- 16%] and 60 min [MVC: (placebo) -10 +/- 11% vs (200 mu g) -11 +/- 6%vs (800 mu g) -8 +/- 20%; TwQ(peak): (placebo) -30 +/- 1 1%vs (200 mu g) -28 +/- 24%vs (800 mu g) -27 +/- 15%] after leg extensions. Treatments did not modify maximal voluntary activation at any time of the protocol. Conclusion: Acute therapeutic or supratherapeutic doses of inhaled salbutamol have no effect on quadriceps strength, fatigue, and recovery in men without asthma.