Effects of Acute Salbutamol Inhalation on Quadriceps Force and Fatigability


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Abstract

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, TwQpeak) 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 μg) or placebo inhalation.Results:Before exercise, treatments had no significant effect on MVC [(placebo) 597 ± 146 N vs (200 μg) 629 ± 151 N vs (800 μg) 610 ± 148 N] and TwQpeak [(placebo) 215 ± 83 N vs (200 μg) 227 ± 69 N vs (800 μg) 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 TwQpeak reductions at 30 min [MVC: (placebo) −8 ± 9% vs (200 μg) −9 ± 7% vs (800 μg) −8 ± 5%; TwQpeak: (placebo) −29 ± 13% vs (200 μg) −23 ± 15% vs (800 μg) −20 ± 8%] and 60 min [MVC: (placebo) −12 ± 17% vs (200 μg) −6 ± 9% vs (800 μg) −8 ± 8%; TwQpeak: (placebo) −20 ± 21% vs (200 μg) −19 ± 23% vs (800 μg) −8 ± 7%] after cycling. Similarly, reductions in MVC and TwQpeak were not significantly different between treatments at 30 [MVC: (placebo) −11 ± 9% vs (200 μg) −12 ± 7% vs (800 μg) −8± 16%; TwQpeak: (placebo) −37 ± 12% vs (200 μg) −33 ± 20% vs (800 μg) −32 ± 16%] and 60 min [MVC: (placebo) −10 ± 11% vs (200μg) −11 ± 6% vs (800 μg) −8 ± 20%; TwQpeak: (placebo) −30 ± 11% vs (200 μg) −28 ± 24% vs (800 μg) −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.

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