Maximum acceptable repetitive lifting workloads for an 8-hour work-day using psychophysical and subjective rating methods

Abstract

The psychophysical method used by Snook (1978) to determine maximum acceptable workloads for repetitive lifting during an 8-hour work-day in industrial populations was evaluated for application in military ergonomics. Under the conditions ofthe present experiment, the mean load selected by 10 soldiers (17·5 kg) was lower than reported by Snook (1978) for industrial workers and by Garg and Saxena (1979) for college students. When the soldiers lifted and lowered their selected load for an 8-hour work-day, the average heart rate was 92 beats min⁻¹ and the mean oxygen cost was 21% of their maximum oxygen uptake (determined for uphill treadmill running). There was no evidence of cardiovascular, metabolic or subjective fatigue. A subjective rating method tended to identify slightly lower loads than the psychophysical method. The results indicate that with good subject cooperation and firm experimental control in a laboratory, the psychophysical method can identify loads that soldiers can lift repetitively for an 8-hour work-day without metabolic, cardiovascular or subjective evidence of fatigue