Effects of acute salbutamol inhalation on quadriceps force and fatigability.
BACKGROUND
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 microg) or placebo inhalation.


RESULTS
Before exercise, treatments had no significant effect on MVC [(placebo) 597 +/- 146 N vs (200 microg) 629 +/- 151 N vs (800 microg) 610 +/- 148 N] and TwQpeak [(placebo) 215 +/- 83 N vs (200 microg) 227 +/- 69 N vs (800 microg) 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 microg) -9 +/- 7% vs (800 microg) -8 +/- 5%; TwQpeak: (placebo) -29 +/- 13% vs (200 microg) -23 +/- 15% vs (800 microg) -20 +/- 8%] and 60 min [MVC: (placebo) -12 +/- 17% vs (200 microg) -6 +/- 9% vs (800 microg) -8 +/- 8%; TwQpeak: (placebo) -20 +/- 21% vs (200 microg) -19 +/- 23% vs (800 microg) -8 +/- 7%] after cycling. Similarly, reductions in MVC and TwQpeak were not significantly different between treatments at 30 [MVC: (placebo) -11 +/- 9% vs (200 microg) -12 +/- 7% vs (800 microg) -8+/- 16%; TwQpeak: (placebo) -37 +/- 12% vs (200 microg) -33 +/- 20% vs (800 microg) -32 +/- 16%] and 60 min [MVC: (placebo) -10 +/- 11% vs (200microg) -11 +/- 6% vs (800 microg) -8 +/- 20%; TwQpeak: (placebo) -30 +/- 11% vs (200 microg) -28 +/- 24% vs (800 microg) -27 +/- 15%] after leg extensions. Treatments did not modify maximal voluntary activation at any time of the protocol.


CONCLUSIONS
Acute therapeutic or supratherapeutic doses of inhaled salbutamol have no effect on quadriceps strength, fatigue, and recovery in men without asthma.
Decorte
Nicolas
N
REX-S Laboratory, Joseph Fourier University and UF Exercise Research, Grenoble University Hospital, Grenoble, FRANCE.
Verges
Samuel
S
Flore
Patrice
P
Guinot
Michel
M
Wuyam
Bernard
B
D000222:Adaptation, Physiological; D000280:Administration, Inhalation; D000420:Albuterol / Q000008:administration & dosage*; D001993:Bronchodilator Agents / Q000008:administration & dosage*; D018592:Cross-Over Studies; D004311:Double-Blind Method; D005080:Exercise Test; D017079:Exercise Tolerance / Q000187:drug effects / Q000502:physiology; D005541:Forced Expiratory Volume; D006801:Humans; D008297:Male; D009119:Muscle Contraction / Q000187:drug effects* / Q000502:physiology; D018763:Muscle Fatigue / Q000187:drug effects* / Q000502:physiology; D053580:Muscle Strength / Q000187:drug effects* / Q000502:physiology; D052097:Quadriceps Muscle / Q000187:drug effects / Q000502:physiology*; D012129:Respiratory Function Tests; D014797:Vital Capacity; D055815:Young Adult
D001993:Bronchodilator Agents; D000420:Albuterol