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

Abstract

The psychophysical method used by Snook to determine maximum acceptable workloads for repetitive lifting during an 8 h work day in industrial populations was evaluated for application in military ergonomics. The mean load selected by 10 soldiers (17.5 kg) was lower than reported by Snook for industrial workers and by Garg and Saxena for college students. When the soldiers lifted and lowered their selected load for an 8 h work day, the average heart rate was 92 beats/min and the mean O2 cost was 21% of their maximum O2 uptake (determined for uphill treadmill running). There was no evidence of cardiovascular, metabolic or subjective fatigue. A subjective rating method identified slightly lower loads than the psychophysical method. With good subject cooperation and firm experimental control in a laboratory, the psychophysical method identified loads that soldiers could lift repetitively for an 8 h work day without metabolic, cardiovascular or subjective evidence of fatigue.