Effect of warm-up exercise on exercise-induced bronchoconstriction.

PURPOSE Exercise-induced bronchoconstriction (EIB) occurs when vigorous exercise induces bronchoconstriction. Preexercise warm-up routines are frequently used to elicit a refractory period and thus reduce or prevent EIB. This study aimed to conduct a systematic review to evaluate the effectiveness of preexercise routines to attenuate EIB. METHODS A comprehensive literature search was performed, with steps taken to avoid publication and selection bias. Preexercise warm-up routines were classified into four groups: interval high intensity, continuous low intensity, continuous high intensity, and variable intensity (i.e., a combination of low intensity up to very high intensity). The EIB response was measured by the percent fall in the forced expiratory volume in 1 s (FEV1) after exercise, and the mean differences (MDs) and 95% confidence intervals (CI) are reported. RESULTS Seven randomized studies met the inclusion criteria. The pooled results showed that high intensity (MD = -10.6%, 95% CI = -14.7% to -6.5%) and variable intensity (MD = -10.9%, 95% CI = -14.37% to -7.5%) exercise warm-up attenuated the fall in FEV1. However, continuous low-intensity warm-up (MD = -12.6%, 95% CI = -26.7% to 1.5%) and continuous high-intensity warm-up (MD = -9.8%, 95% CI = -26.0% to 6.4%) failed to result in a statistically significant reduction in bronchoconstriction. CONCLUSIONS The most consistent and effective attenuation of EIB was observed with high-intensity interval and variable intensity preexercise warm-ups. These findings indicate that an appropriate warm-up strategy that includes at least some high-intensity exercise may be a short-term nonpharmacological strategy to reducing EIB.