Pulmonary function changes following exercise.

Many studies have documented differing changes in forced vital capacity (FVC) following various intensities and durations of exercise. This investigation used three different intensities and durations of treadmill running, with subjects who were active runners, with the intent of finding an intensity or duration that might elicit changes in FVC and if these changes are related to respiratory muscle fatigue. Intensities and durations included a graded maximal test to exhaustion (7-14 min); a 7-min test at 90% of maximal VO2, and a 30-min test at 60% of maximal VO2 (intensity). Maximal inspiratory pressures (MIP), maximal expiratory pressures (MEP), forced expiratory volume in 1 s (FEV1.0) and FVC were measured pretest, and 5, 10, and 30 min post-test (time). MIP was not different across time or intensities. The decrease in MEP approached significance at 10-min post-exercise compared to pretest values (P = 0.0569), with no differences found between intensities. FVC was different between times (P = 0.0117) but not between intensities. FVC was decreased at 5 and 10 min post-test compared with pre and 30 min. FEV1.0 was significantly reduced at 5 and 10 min post-test compared with pretest. These data suggest that a combination of duration and intensity may be necessary to elicit pulmonary function changes after exercise and that expiratory muscle fatigue may be a factor that results in a reduced FVC.