The Energy Expended While Walking in Stooping Postures

In mine roadways the roof is frequently so low that it is impossible to walk in the natural erect manner and it is necessary to stoop, sometimes to a considerable extent. Indeed, in a very low place it may be necessary to travel some distance on all fours. Walking in low roadways can be very fatiguing when a pronounced stoop is necessary, for the energy cost of walking in such a posture is greater than that incurred in walking in the usual erect posture at the same speed. In a study of the energy output of coal-miners during work Moss (1935) made observations of the oxygen intake during walking in different postures along a level floor at a constant speed of 34 miles per hour. His subjects were eight miners, all trained rescue men, who were accustomed to wearing a mouthpiece and nose-clip and were also used to low roadways. Experiments were made with the subjects walking in four postures: (a) erect; (b) in a posture referred to as "half stoop", in which the subject stooped enough to reduce his height by about 20%; (c) " full stoop ", in which the height was reduced by 40% ; and (d) " all fours ", in which the subject walked on hands and feet and reduced his height by about 50%. Moss concluded that the energy cost of walking at 34 miles per hour in the half-stoop posture was about 20%, in the full-stoop posture 66%, and on all fours about 73% more than the cost of walking erect, and he remarked that the wastage of energy due to walking along low roadways must make an appreciable difference to a man's output of work at the coal face. From the brief mention of the experimental technique given in Moss's paper it appeared that the energy cost with the greater reductions of height was underestimated. Three expiratory air samples of three-, twoor one-minute duration, according to the exacting nature of the work, were taken and averaged, and the average values of oxygen intake thus determined were taken as representing the energy output when walking in the various postures. No allowance appears to have been made for the large oxygen debt which is incurred during a short bout of such violent exercise as progressing on all fours at 34 miles an hour. Moss's results appeared to be of some practical significance, and soon after they were published we made a series of observations on ourselves in which we walked at various speeds and as nearly as possible in the postures described. In view of the attention now being devoted to the physiological problems of mining, it may be of some interest to report the results of those observations.