Effect of heavy load carriage on respiratory mechanics and breathing pattern during graded exercise

Abstract

The effect of heavy load carriage on pulmonary function at rest and on breathing pattern and lung volumes during graded exercise was studied. Fifteen males completed treadmill tests to measure VO2peak with and without a 25-kg pack. Subsequently, each subject completed short periods of treadmill walking in loaded and unloaded conditions at intensities equivalent to 55, 65, 75 and 85% of VO2peak. At rest, in the loaded condition, forced vital capacity (FVC) and forced expiratory volume in one second (FEV1) both were reduced by 3% with no change in FEV1/FVC. During exercise with the pack, tidal volume (VT) and end-inspiratory lung volume (EILV) were reduced by 14 and 5%, respectively, while ventilation (VE) was maintained by a 9% increase in breathing frequency (Bf). Rating of perceived exertion (RPE) was always higher during the loaded trial, despite identical oxygen consumption (VO2) and heart rate (HR) responses. During graded exercise under heavy load up to 85% of VO2peak, breathing pattern is altered to maintain VE while respiratory mechanics were not altered.