Metabolic and cardiovascular cost, and perceived effort over an 8 hour day when lifting loads selected by the psychophysical method

Abstract

The psychophysical method used by Snook [576] to determine maximum acceptable workloads for repetitive lifting during an 8 hour workday in industrial populations was evaluated for application in military ergonomics. Under the conditions of the present experiment, the mean load selected by 10 soldiers (17-5 kg) was lower than reported by Snook [576] for industrial workers, and by Garg and Saxena [243] for college students. When the soldiers lifted and lowered their selected load for an 8 hour workday, 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. The results indicate that with good subject co-operation and firm experimental control in a laboratory, the psychophysical method can identify loads that soldiers can lift repetitively for an 8 hour workday without metabolic, cardiovascular or subjective evidence of fatigue, but it is not clear to what extent this is a maximum workload consistent with a physiological steady state.