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 (20-30yrs) 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 (FEV(1.0)), forced expiratory flow (FEF(75-85)), 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 FEV(1.0) and FEF(75-85) 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.