INFLUENCE OF A BETA(2)-AGONIST ON PHYSICAL PERFORMANCE AT LOW-TEMPERATURE IN ELITE ATHLETES

beta(2)-Agonists are frequently used by elite cross-country skiers, a group Of athletes with a high prevalence of asthma. It has been claime d that beta(2)-agonists have a positive effect on physical performance . The aim of the present study was to investigate whether inhalation o f a beta(2)-agonist increases physical performance at low temperature in healthy, nonasthmatic athletes with normal bronchial responsiveness . Twenty elite male athletes (cyclists, cross-country skiers, middle a nd long distance runners) with no history of allergy or airway disease and who had normal spirometry and methacholine bronchial provocation tests performed a maximal exercise test on a treadmill in a climate ch amber at similar to 10 degrees C on two subsequent days. Before exerci se they inhaled terbutaline (3 mg from MDI) or placebo in a randomized , single blind manner. After 10-min warm-up on the treadmill, a submax imal work preceded a stepwise increase of the workload until exhaustio n. Lung function, ventilation, oxygen uptake, and heart rate were dete rmined and blood samples for lactate and potassium analyses were drawn before, during, and after exercise. Terbutaline induced a significant bronchodilatation; FEV1 increased from 4.8 (4.4-5.1)L to 5.0 (4.6-5.4 ) L, mean (95% CI). There were no significant differences between the two treatments with regard to exercise time, 25.1 (24.3-25.8) min vs 2 4.9 (24.1-25.6) min, oxygen uptake and ventilation during exercise, or heart rate at maximal workload. Terbutaline induced an increase in se rum lactate concentration but did not influence the lactate response t o exercise. The serum potassium increase was attenuated at low work lo ad but not at maximal work. The postexercise decrease in serum potassi um concentration was significantly greater after terbutaline (-0.52 (- 0.29 to -0.76) mmol.L-1) than after placebo (-0.13 (0.06 to -0.32) mmo l.L-1 (P < 0.001). We conclude that inhalation of a beta(2)-agonist (t erbutaline) in a dose that yields significant bronchodilatation does n ot influence physical performance at low temperature in healthy athlet es. Acute inhalation of the beta(2)-agonist amplified the postexercise hypokalemia, a finding of unclear significance. Although there is a s light bronchodilatation and potential negative airways effect of cold air inhalation, a beta(2)-agonist does not increase physical performan ce in top athletes.