Energy Expenditure of Heavy Load Carriage

Abstract

Fourteen subjects (22 yr, 175 cm, 72 kg) walked for 20 min on a treadmill at 3-2, 4-8, or 64 km h^-1 carrying 35, 40, 45, or 50 kg; during a second phase, ten additional subjects (22 yr, 178 cm, 75 kg) attempted to walk for 45 min at the same speeds carrying 60, 65. or 70 kg Energy expenditure when expressed as cm³ oxygen per minute per kilogramme of total weight (man + clothing + load) agreed, for the no load condition, with literature values. After deducting the individual's no load cost, the resulting net energy expenditure for carrying the loads, when expressed as cm³ kg^-1 min^-1 was generally constant at each speed; i.e. loads from 35 to 70 kg showed no statistical differences in energy expenditure per kilogramme at 3 2 and 4 8 km h^-1. At 6-4 km h^-1 carrying 70 kg, the average measured cost per kg was statistically different (p < 005) than carrying 35 kg at this speed; subjects were working at greater than 90% of their maximal [Vdot]₀₂ levels carrying 70 kg. However. similar comparison of the measured cost per kg between loads of 40 and 65 kg was statistically the same at 6 4 km h^-1. The general constancy of measured energy expenditure per kg for loads even up to 70 kg, probably depends on the condition that the load is well balanced and close to the centre of the body. As reported earlier, higher costs are associated with loads in unbalanced positions. Thus, the limitations commonly encountered in load carrying capacity may arise from poor positioning of the load rather than from the weight of the load per