['To determine if a heart rate-based protocol for bronchial provocation testing ensures sufficient exercise intensity for inducing exercise-induced bronchial obstruction.', '100 clinically healthy non-asthmatic sports students.', 'Subjects underwent an exercise challenge test (ECT) on a treadmill ergometer for bronchial provocation according to the guidelines of the American Thoracic Society (ATS). Heart rate (HR), forced expiratory volume in 1 second (FEV(1)), pH (pH) and lactate concentration were measured before and after exercise.', 'After exercise in 56% of the examined subjects lactate concentrations were < 6 mmol/l. A highly significant decrease in FEV(1) (mean -4.41 (SD 1.5%)) was found at concentrations of > 6 mmol/l, whereas at concentrations < 6.48 mmol/l, no participant showed an impairment of lung function (FEV(1) values < or = 90%). In five subjects, a bronchial obstruction was found, as shown by decreases in FEV(1) of -10 to -47% after exercise. The lactate concentrations in these individuals were between 6.48 and 11.7 mmol/l, indicating a predominantly anaerobic metabolic response to exercise.'] Do heart rate-based protocols for exercise challenge testing ensure sufficient exercise intensity for inducing exercise-induced bronchial obstruction?