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

Prolonged physical exertion is regulated subjectively by the perception 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 underwent incremental and 30-minute endurance lifting tests. Cardiorespiratory parameters were monitored with an oxygen uptake analyser and mechanical parameters were calculated using a lift dynamometer. Ratings of perceived exertion were given on Borg's 10-point scale. Physiological responses to repetitive lifting Were matched with subjective perceptions. The relationship between the perception of exertion nd the duration of the endurance tests was descried by power functions; Y = aX(n), in which 0 > n > 1. A single-variable statistical regression for power functions was performed to obtain the individual 'iso-perception' curves as functions of the mechanical work exerted. It was found that the 'iso-perception' curve corresponding to a 'moderate' perception of effort may represent the individual 'tolerance threshold' for prolonged lifting tasks, since physiological responses at this intensity of effort did not change significantly and the respiratory exchange ratio was less than one. The individually tolerable power over time for lifting tasks has been estimated.