The effect of vertical load placement on metabolic rate during loaded walking in humans

We examined the effects of vertical load placement on the metabolic cost of walking. Twelve healthy participants walked on a treadmill with 13.8 and 23.4 kg loads in both high and low vertical positions. Metabolic rate was measured using respirometry. While load position had no effect on the net metabolic rate for the 13.8 kg load, the net metabolic rate with the 23.4 kg load was significantly reduced by 4.3% in the high vertical load position compared to the low vertical load position. Loads carried higher on the trunk were also associated with increased forward trunk lean that reduced the load gravitational moment arm in the sagittal plane suggesting that reduction of fore-aft upper body torques is an energy-saving mechanism during loaded walking. Practitioner Summary: Load placement within a backpack affects the biomechanics of load carriage. We experimentally tested the metabolic cost of high and low load placement during walking and found the high position to be less costly with large loads. Loading high may be the optimal technique for carrying heavy backpacks.