TOLERABILITY TO PROLONGED LIFTING TASKS ASSESSED BY SUBJECTIVE PERCEPTION AND PHYSIOLOGICAL-RESPONSES

Prolonged physical exertion is regulated subjectively by the perceptio n of effort. This preliminary study was conducted to validate the use of subjective perceptions of effort in assessing objectively tolerable workloads for prolonged lifting tasks. Eight healthy male subjects un derwent incremental and 30-minute endurance lifting tests. Cardiorespi ratory parameters were monitored with an oxygen uptake analyser and me chanical parameters were calculated using a lift dynamometer. Ratings of perceived exertion were given on Borg's 10-point scale. Physiologic al responses to repetitive lifting Were matched with subjective percep tions. The relationship between the perception of exertion nd the dura tion of the endurance tests was descried by power functions; Y = aX(n) , in which 0 > n > 1. A single-variable statistical regression for pow er functions was performed to obtain the individual 'iso-perception' c urves as functions of the mechanical work exerted. It was found that t he 'iso-perception' curve corresponding to a 'moderate' perception of effort may represent the individual 'tolerance threshold' for prolonge d lifting tasks, since physiological responses at this intensity of ef fort did not change significantly and the respiratory exchange ratio w as less than one. The individually tolerable power over time for lifti ng tasks has been estimated.