Breathing patterns and heart rate during simulated occupational upper limb tasks in normal subjects.

Abstract

Despite the arms being used extensively in the performance of many occupational tasks, little is known about the pattern of breathing and physiological cost of such work. The purpose of this study was to establish whether a simple change in arm support could alter the workload, pattern of breathing and respiratory muscle recruitment during a low intensity arm task. Ten normal subjects performed a simulated work task when sitting, once with the arms supported and once unsupported. Subjects were required, over a five-minute period, to repeatedly pick up a 2 kg object, inspect and hold it for 15 seconds and then pack it in a box. Breathing pattern responses, measured by pneumotachograph and respiratory inductive plethysmography, were minute ventilation (VE), respiratory frequency (Rf), tidal volume (VT) and change in functional residual capacity (FRC). The main findings were that unsupported arm work was more physiologically demanding than supported arm work. During work VE increased as a result of a change in respiratory frequency but not VT which was much more limited when the arms were unsupported. At the completion of activity, when the arms were unloaded, VT initially increased as VE decreased. FRC and VT were reduced during arm work and increased during recovery, mainly as a result of a change in ribcage excursion. These findings support the theory that during arms activity, intercostal and accessory respiratory muscles act to stabilize the arms and torso, impeding chest wall movement and shifting the respiratory load from these muscles to the diaphragm. This may adversely effect performance of workers who have ventilatory limits to arm work tasks.