Standardization of work intensity for evaluation of exercise-induced bronchoconstriction.

Reactivity of airways to 6 min of graded intensity treadmill work was studied in nine asthmatic and 15 non-asthmatic subjects. After performing a progressive VO2 max treadmill test, each subject completed five 6-min exercise tests at selected intensities: 40, 60, 80, and 100% VO2 max; and at 80% of VO2 max predicted from heartrate. Pulmonary function measures recorded after exercise demonstrated a direct relationship between work intensity and exercise induced bronchoconstriction (EIB) for both groups, with the asthmatics showing their lowest values at 80% VO2 max. Heartrate-set work intensities produced a wide range of aerobic demand, thus significantly increasing the variability of the EIB response recorded.