Exercise-induced bronchoconstriction depends on exercise load

Exercise-induced bronchoconstriction (EIB) is often used as a measure of br onchial hyperresponsiveness and employed in epidemiological studies. Differ ent tests are used, including free running tests with poor standardization of exercise load. The present study aimed to assess the role of exercise lo ad in relationship to level of EIB. Methods: 20 asthmatic children, 9-17 years old with a history of EIB, under went two treadmill test with 85% and 95% exercise load. The children ran wi th increasing speed for the first 2 min until reaching a heart rare of 85% or 95% of calculated maximum (220 - age) and maintained this speed for the last 4 min. Lung function was measured before running, and 0, 3, 6, 10 and 15min after the run. Borg scale for perceived exertion was employed for chi ldren's self-evaluation of exercise load. Results: Peak heart rate, mean Borg score during 85% exercise load was 178. 7/13.6 and during 95% was 194.3/18.2 (P<0.001). Maximum fall in FEV1 after 85% exercise load was 8.84% vs. 25.11% after 95% (P<0.001). Nine subjects ( 40%) fell greater than or equal to 10% in FEV1 after 85% exercise load vs. 20 subjects (1009/0) after 95% exercise load. EIB from the 95% exercise loa d test had markedly higher correlation with serum ECP (r=0.77, P<0.001). Conclusion: Exercise load is essential for the interpretation of EIB, and s trict standardization of exercise tests should be undertaken. The EIB from the high exercise load tests seemed better correlated to inflammatory activ ity than the low exercise load test.