The Energy Expenditure of Coal Miners at Work

Abstract

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.The coal-mining industry of Great Britain, one of the largest "heavy" industries in the world, employs well over two hundred thousand men at the coal-face alone, and more than that number elsewhere underground. Many among this large labour force expend energy daily in quantities that are greater than in most other large industrial concerns. A need to be able to estimate the energy production of miners working in different collieries, where physical conditions and the rate and pattern of work vary, led to the present investigation; it forms an integral part of a programme of research intended to determine thermal environmental conditions for everyday work at the coal-face (Lind, 1960) in which the contribution of metabolic heat to the total heat load would certainly be substantial. For this purpose it is desirable to know not only the man's total energy production in the course of a shift, but also the extent to which it varies from hour to hour.Generally, the measurement of energy expenditure of man in the course of his daily activities has been related either to his food requirements, or to the rearrangement of his work in such a way as to permit greater efficiency and productivity, coupled, if possible, with a reduction in the physiological strain. For these reasons the energy expenditures involved in some mining tasks have previously been reported from the East Midlands by Moss (1935), from Germany by Lehmann, Muller, and Spitzer (1950), and from Italy by Granati and Busca (1941). These earlier investigations into the energy cost of coal-mining are not entirely satisfactory as working conditions have changed much since the time of Moss, and foreign surveys made on men subjected ...