Influence of carrying heavy loads on soldiers' posture, movements and gait

Military personnel are required to carry heavy loads whilst marching; this load carriage representing a substantial component of training and combat. Studies in the literature mainly concentrate on physiological effects, with few biomechanical studies of military load carriage systems (LCS). This study examines changes in gait and posture caused by increasing load carriage in military LCS. The 4 conditions used during this study were: control (including rifle, boots and helmet carriage, totalling 8 kg), webbing (weighing 8 kg), backpack (24 kg) and a Light Antitank Weapon (LAW, 10 kg), resulting in an incremental increase in load carried from 8, 16, 40 to 50 kg. Twenty male soldiers were evaluated in the saggital plane using a 3-dimensional CODA™ motion analysis system. Measurements of ankle, knee, femur, trunk and craniovertebral angles and spatiotemporal parameters were made during self-paced walking. Results showed spatiotemporal changes were unrelated to angular changes, perhaps a consequence of military training. Knee and femur ranges of motion (control, 21.1º ±3.0 and 33.9º ±7.1 respectively) increased (p<0.05) with load (LAW, 25.5º ±2.3 and 37.8º ±1.5 respectively). The trunk flexed significantly further forward confirming results from previous studies. In addition, the craniovertebral angle decreased (p<0.001) indicating a more forward position of the head with load. It is concluded that the head functions in concert with the trunk to counterbalance load. The higher muscular tensions necessary to sustain these changes have been associated with injury, muscle strain and joint problems.