The energy expenditure of coalminers at work.

This survey was intended to provide a basis of information on the energy expenditures for the main component tasks in coal-mining, carried out at different rates and in different postures. Such information is frequently required for studies of the physiological effects of coal-mining; these values reported here were required in particular for studies intended to define thermal limits of the environment suitable for miners at non-mechanized coal-faces, a situation where the metabolic heat produced makes up a large proportion of the total heat load of the individual. Regression lines have been drawn between energy expenditure and speed of shovelling for the miner working in different postures. When forced to work lying on the floor the man's energy expenditure dropped, but his coal output also dropped. Walking to and from the coal-face along roadways of good height yielded energy expenditures comparable to those of treadmill walking, although generally slightly higher in value. Stooped walking generally increased the energy expenditure ofwalking, but to a smaller extent than was anticipated from previous laboratory work. Several time analyses of complete shifts from different collieries, in which the time spent at different tasks had been measured, yielded an average estimate of the energy expenditure for an eight-hour shift of 2,000 kcal.