Comparison of bronchoconstriction induced by cycling and running.

Bicycle ergometer, treadmill, and free range running exercise have been used to induce bronchoconstriction in 10 asthmatic subjects who were relatively well and free from symptoms at the time of study. Comparisons have been made with normal subjects under similar laboratory conditions. Bronchoconstriction was measured by peak expiratory flow rate before, during, and after each test. Ventilation, pulse rate, and gas exchange were also measured. The work involved in the different types of exercise was matched to produce similar ventilation and pulse rates for any one subject. Exercise-induced bronchoconstriction was significantly less on the bicycle ergometer than on running (treadmill or free range). The normal subjects showed less than one quarter the bronchial lability of the asthmatic subjects in any one test. All subjects had lower respiratory exchange ratios during running compared with cycling and this appeared to correlate with the bronchial lability in the asthmatics, who also had rather higher pulse rates during running. Running involves a proportion of high-efficiency negative work which might partly account for the observed differences.