The Additivity of Values of Energy Expenditure of Simultaneously Performed Simple Muscular Tasks

A study was carried out to compare the sum of independently determined net rates of energy expenditure for two or three simple muscular tasks and the net rate of energy expenditure for the simultaneous performance of the same tasks. Three simple tasks were used: one-armed cranking of an ergometer, one-armed static pulling against resistance, and walking. Eight configurations representing all possible combinations of the simple tasks were examined. The results showed that for seven of the eight configurations, the sum of the net rates of energy expenditure for the simple tasks significantly exceeded the net rate of energy expenditure for simultaneous performance. For four of these configurations, the discrepancy was 20 per cent or larger. The results are discussed in terms of kinesiology, i.e. the science of movement of the body, and their implications for both work design and possible systems of standard metabolic data.