Comparison of the bronchial response to running and cycling in asthma using an improved definition of the response to work.

The bronchial responses to treadmill running and ergometer cycling have been compared in 13 adults with asthma. The exercises were performed on separate days with an interval ranging from three days to six months. The study was designed to ensure that the time course of oxygen consumption during running was replicated during cycling. The response to exercise was estimated by taking serial measurements of the maximum forced expiratory flow rate and forced expiratory volume in one second before and after work. Indices used to describe the response were (b-a)/b and a/b, where b and a were the average lung function before and the lowest value after exercise respectively. There was no significant difference in the lung function of the subjects before running and cycling nor did the duration of exercise or oxygen consumption differ between the two exercises. Eleven of the 13 patients showed a reduction in ventilatory capacity after both forms of exercise. Differences in the lung function responses to the two forms of standard work were trivial and not statistically significant, amounting to only about 1%. It is suggested that previous reports of larger responses to running than cycling were probably due to higher energy expenditures during running. General problems regarding the description and comparison of the responses to exercise are discussed.