Hip-belt load sharing reduces peak shoulder pressure across walking slopes during heavy load carriage

Abstract

Musculoskeletal injury to the spine and lower back resulting from heavy load carriage (30–40 kg) is common among military service members. Static peak pressure is a reliable parameter for predicting discomfort. The effect of using a hip belt on shoulder pressure is not well understood. This study aimed to quantify the pressure under shoulder straps when carrying a backpack with and without a hip belt. Three military service members wore a helmet and body armor (~6.5kg) and carried a backpack in two attachment conditions: (1) entirely shoulder borne, and (2) with a hip-belt engaged, all totaling 40% body weight. Participants walked at three different slope conditions (10° downhill, level, and 10° uphill) at 1.15 m/s for each backpack condition. Peak pressure across both shoulders was extracted from each condition. Shoulder borne peak pressure (down: 36.33 kPa; level: 37.67 kPa; up: 36.67 kPa) was greater than the hip belt (down: 29.67 kPa; level: 24.67 kPa; up: 29.67 kPa). Walking with the hip belt engaged compared with the shoulder borne-only backpack resulted in ~9 kPa smaller peak shoulder pressure on average across all three slopes, indicating that peak pressure is reduced when using a hip belt, although greater participant numbers are needed to confirm these results.