Residual lung volume and ventilatory muscle strength changes following maximal and submaximal exercise

In order to evaluate a mechanism which may be responsible for the often observed acute increase in residual lung volume (RV) following exercise, 12 non-smoking males (20-30 yrs) performed two bouts of exercise on separate days; one to maximal heart rate (HRmax) and one to 85% of HRmax for 20 min. Prior to exercise and at 5, 15, 30, 60 and 120 min post-exercise, the following parameters were measured: RV, forced vital capacity (FVC), forced expiratory volume (FEV1.0), forced expiratory flow (FEF75-85), maximal expiratory pressure (PEmax), and maximal inspiratory pressure (PImax). Significant (p < 0.05) increases occurred in RV at 5, 15 and 30 min following maximal exercise and at 5 and 30 min after submaximal exercise. Changes in RV between the two exercise bouts were generally greater (p < 0.05) for maximal exercise. Accompanying the increases in RV were significant (p < 0.05) decreases in PEmax and decreases in FVC, while FEV1.0 and FEF75-85 remained generally unchanged or were slightly elevated. The data suggest that decreases in expiratory muscle strength due to fatigue may in part be responsible for increases in RV.