Strain while skiing and hauling a sledge or carrying a backpack

SummaryEight soldiers on skis transported three loads of different weights on the level, uphill and downhill. The load was placed either on a cargo sledge or in a backpack or divided between the sledge and the backpack. The sledge had a new type of haulage-shaft, which was fixed to both sides of the pelvis. A service belt spread the pull over the whole upper body. The physical strain of different transport methods and the serviceability of the sledge was studied by measuring heart rate (HR), oxygen consumption, ventilation, and perceived exertion. The results indicate that both absolute and relative strain were systematically lower when pulling the load on the sledge than when carrying it in the backpack and on the sledge. HR when pulling a load equal to the human body weight on the sledge was on average 133 beats · min−1; HR was significantly higher 144 beats · min−1 when the load was divided between backpack and sledge. At the lower load level the differences between the transport methods were not significant for HR, oxygen consumption or ventilation. Uphill travel increased oxygen consumption by about 50% over that on the level. Perceived exertion at all load levels was significantly lower with the sledge than with the backpack alone or in combination. The estimated maximal allowable working time emphasized the advantage of the sledge and the importance of high physical working capacity. The manoeuvrability of the sledge with the new haulage shaft was good and the braking mechanisms worked well. The results imply that a man with normal working capacity is able to transport a load equal to his own weight for about 2.5 km without overstrain by pulling it an a sledge on the level. This result is valuable for the planning of field medical services.