Biomechanics of Load Carriage

Abstract

Loads carried by the Warfighter have increased substantially throughout recorded history, with the typical U.S. ground Soldier carrying external loads averaging 45 kg during recent conflicts. Carrying heavy loads is one potential source of injury that has been researched from a performance and epidemiological perspective. This chapter focuses on the biomechanics of military load carriage, primarily focusing on lower extremity joint stresses and potential overuse injury mechanisms that may be associated with carrying a load. Studies into the biomechanics of load carriage have documented motion-related differences such as increased step rate, decreased stride length, and more trunk lean with increases in pack-borne loads. Ground reaction forces have been found to increase proportionately with loads up to 40 kg. However, there is a paucity of literature on the relationship between load carriage and biomechanical mechanisms of overuse injury. Findings of recent studies will be presented which add mechanistic information to increased stresses on the lower extremity. Efforts to model injury mechanisms require continued biomechanical measurements in humans while carrying occupationally-relevant loads in order to be validated. In addition to lab-based biomechanics data needed to further explore the mechanistic relationship between load magnitude and injury, technologies should be exploited to accurately quantify stresses related to load carriage the field.