Influence of a 12.8-km military load carriage activity on lower limb gait mechanics and muscle activity

Abstract

The high stress fracture occurrence in military populations has been associated with frequent load carriage activities. This study aimed to assess the influence of load carriage and of completing a load carriage training activity on gait characteristics. Practitioner Summary:This study identified gait changes due to load carriage and after a military load carriage training activity. Such activities are associated with lower limb stress fractures. A prepost study design was used. Gait mechanics changed to a greater extent when carrying load, than after completion of the activity when assessed without load.

The Effects on Muscle Activity and Discomfort of Varying Load Carriage With and Without an Augmentation Exoskeleton

“…It is therefore unclear whether a longer ground contact time is associated with the development of injury, or if it is a mechanism to minimize the risk of injury. Therefore, interventions for increasing muscular strength and endurance of the plantar flexor and knee extensor muscles may be beneficial [2].…”

“…Regular load carriages are criteria risk factors for Muscular Skeletal Disorders (MSDs) in hikers, backpackers, and soldiers [1,2]. The prevalence of MSDs is significantly related to the weight and mode of carrying a backpack among the load carrying population [3].…”

Sagittal and Frontal Plane Knee Angular Jerk Effects During Prolonged Load Carriage

“…Both vertical and sagittal ground reaction force increase with the presence of body borne load, with peak ground reaction force increasing significantly at as low as a 20 kg load, resulting in changes up the kinetic chain [13][14][15][17][18][19] . Previous studies have shown mixed results regarding the range of motion of sagittal plane knee range of motion while walking with body borne load, but knee flexion has consistently been shown to increase with the addition of body borne load to help stabilize the knee 7,[12][13][14]18,19,22,[56][57][58] . In order to stabilize the knee, knee flexion helps the body lower the center of mass, but this also increases the forces and torques on the knee, increasing loading on the soft tissues at the knee 7,12,[14][15][16]18 .…”

“…As fatigue increases, stride time and length decrease, and ground contact time and step width variability increases 31,58,69 . While these alterations help stabilize the body, these are factors that indicate a decrease in stability during muscular fatigue.…”

“…Also, muscle function at the knee decreases after a prolonged period of time, which can increase the risk of musculoskeletal injury 58,71 . Energy cost and rate of perceived exertion also increase over time during prolonged load carriage, as seen by an increase in VO2,max and an increase in heart rate 11,33,72 .…”