Abstract

Approximately half of all asthmatics become refractory to exercise-induced bronchoconstriction (EIB) with repeated challenges. Exercise refractoriness has been utilized by asthmatic athletes to reduce the bronchoconstrictor response to exercise prior to competition, and this has led to the observation that some asthmatic athletes can “run through” their asthma. The main aim of this study was to investigate the efficacy of short high-intensity, repeated warm-ups compared with salbutamol (a commonly used inhaled β2-agonist) on the severity of EIB. Eight moderately trained (VO2peak, 51.9 ± 2.3 ml/kg/min) recreational asthmatic athletes with documented EIB were tested under 4 experimental conditions: 1) control (CON) condition; 2) an interval warm-up (WU) consisting of 8 × 30-sec runs at peak treadmill speed, with 45-sec recovery between each sprint; 3) inhaling 200 µg of salbutamol (Ventolin®, GlaxoSmithKline, Uxbridge, Middlesex, U.K.) (IH); and 4) combining both the WU and IH session. All 4 experimental sessions were followed by an exercise challenge test (85 - 90% predicted maximum heart rate for 8 min). Pulmonary function was measured pre-exercise and at 1, 5, 10, 15 min postexercise. The mean maximum percent fall in pre- to postexercise forced expiratory volume in 1-sec (FEV1) for all 8 asthmatic subjects during the EIB screening test (CON session) was -18.25 ± 4.01%. The mean maximum percent decrease in postexercise FEV1 significantly decreased (p<0.05) to only - 9.1 ± 0.6 % following the WU condition, which is below the EIB diagnostic threshold of a 10% fall in postexercise FEV1. The IH and WU + IH condition resulted in a substantial postexercise bronchodilation as shown by a significant increase (p<0.05) in the mean maximum percent change in postexercise FEV1 following the IH (+ 8.9 ± 6.1%) and WU + IH (+ 15.2 ± 4.6%) condition. Similar changes as a result of experimental condition were observed for FEF25 - 75 %. These data indicate that repeated high-intensity warm-ups can lessen the bronchoconstrictor response to exercise. In addition, combining the interval warm-up with salbutamol prior to exercise resulted in substantial bronchodilation and conferred a greater protective effect against developing EIB than either intervention alone. Verf.-Referat