The effect of loads carried on the shoulders.

This work describes a way of measuring the forces acting on the shoulders when subjects carry a backpack. A frame pack was carried by 12 male subjects: 4 hikers, 4 occasional hikers, and 4 novices. They walked for 30 minutes on a 5% inclined treadmill at 3.6 km/h to simulate moderate hiking. The load was carried at T9 and was increased (10, 15, and 20 kg) after 1, 20, and 25 minutes. The data from force transducers placed on the shoulder straps were collected for 30 seconds at 100 Hz. Shoulder strain appeared to be the limiting factor in load carriage. The optimal carrying method depends on the person, but it has been shown that decreasing stride length and wearing appropriate footwear reduces the strain on the shoulders.