Heart rate-based protocols for exercise challenge testing do not ensure sufficient exercise intensity for inducing exercise-induced bronchial obstruction

Abstract

Objective: To determine if a heart rate-based protocol for bronchial provocation testing ensures sufficient exercise intensity for inducing exercise-induced bronchial obstruction.

Participants: 100 clinically healthy non-asthmatic sports students.

Design: 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 (FEV₁), pH (pH) and lactate concentration were measured before and after exercise.

Results: After exercise in 56% of the examined subjects lactate concentrations were <6 mmol/l. A highly significant decrease in FEV₁ (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 (FEV₁ values ≤90%). In five subjects, a bronchial obstruction was found, as shown by decreases in FEV₁ 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.

Conclusion: These results show that the ATS standard protocol, using a heart rate formula for assessing the exercise intensity, is not sufficient to cause predominantly anaerobic lactate metabolism and hence exercise-induced hyperventilation. Therefore, a potential bronchial obstruction could not be induced in 56% of the subjects. For a sensitive study design, exercise intensities demanding anaerobic lactate metabolism should always be ensured. A more precise protocol is required.