Physical work load in modern mining.

Following our Institute's involvement in the physiology of mining work (since 1953), this paper deals with underground work load investigated in terms of time, energy expenditure and heart rate in coal miners working with various types and degrees of mechanization. Results showed that a chamber coal face and at heading (coal or sterile rock) mechanization of haulage and loading (conveyor belt and loading machine) led to 50 -- 100 kcal reduction of energy expenditure/hour. At longwall faces, mechanization of haulage (by conveyor) or hewing and loading (with drum-combine) shortened shoveling time, while there was an increase of manual work in the tasks of supporting which was conducive to metabolic rates of 300 kcal/hour. In the case of fully mechanized coal working, including supporting, there was a significant decrease of energy expenditure.