Ventilatory responses in males and females during graded exercise with and without thoracic load carriage.

Abstract

To compare the effects of thoracic load carriage on the ventilatory and perceptual responses to graded exercise, 14 pairs of height-matched, physically active males and females completed randomly ordered modified Balke treadmill exercise tests with and without a correctly sized and fitted 20.4kg backpack and work clothing. Subjects walked at 1.56m.s- 1 while grade was increased by 2% every 2min until exhaustion. Ventilatory responses were measured with open circuit spirometry and perceptual responses were evaluated using the modified Borg scale. Inspiratory capacity maneuvers were performed to calculate operating lung volumes. Despite height matching, males had significantly greater lung volumes and peak oxygen uptake ([Formula: see text]O2peak). Peak [Formula: see text]O2 and ventilation ([Formula: see text]E) were lower (p < 0.05) for all subjects under load. Throughout exercise, the ventilatory equivalents for [Formula: see text]O2 and carbon dioxide production were significantly higher in females, independent of condition. At similar relative submaximal intensities (%[Formula: see text]O2peak), there was no difference in [Formula: see text]E between conditions in either group, however, all subjects adopted a rapid and shallow breathing pattern under load with decreased tidal volume secondary to lower end-inspiratory lung volume. The relative changes in breathing pattern and operating lung volume between unloaded and loaded conditions were similar between males and females. Females reported significantly higher dyspnea ratings for a given [Formula: see text]E compared to males; however, the relationship between dyspnea and [Formula: see text]E was unaffected by load carriage. The relative response patterns for ventilatory and perceptual responses to graded exercise with thoracic loading were similar in males and females.