Abstract
Musculoskeletal injuries (MSI) in the military reduce soldier capability and impose substantial costs. Characterizing biomechanical surrogates of MSI during commonly performed military tasks (e.g., load carriage) is necessary for evaluating the effectiveness of possible interventions to reduce MSI risk. This study determined the effects of body-borne load distribution, load magnitude, and walking speed on tibiofemoral contact forces. Twenty-one Australian Army Reserve soldiers completed a treadmill walking protocol in an unloaded condition and wearing four armor types (standard-issue and three prototypes) with two load configurations (15 and 30 kg) for a total of 8 armor x load ensembles. In each ensemble, participants completed a 5-minute warm-up, and then walked for 10 minutes at both moderate (1.53 m⋅s-1) and fast (1.81 m⋅s-1) speeds. During treadmill walking, three-dimensional kinematics, ground reaction forces, and muscle activity from nine lower-limb muscles were collected in the final minute of each speed. These data were used as inputs into a neuromusculoskeletal model, which estimated medial, lateral and total tibiofemoral contact forces. Repeated measures analyses of variance revealed no differences for any variables between armor types, but peak medial compartment contact forces increased when progressing from moderate to fast walking and with increased load (p<0.001). Acute exposure to load carriage increased estimated tibiofemoral contact forces 10.1 and 19.9% with 15 and 30kg of carried load, respectively, compared to unloaded walking. These results suggest that soldiers carrying loads in excess of 15 kg for prolonged periods could be at greater risk of knee MSI than those with less exposure.
Highlights
Lower-limb musculoskeletal injuries (MSI) reduce soldier capability and impose substantial costs on the person and military, i.e., rehabilitation and salary compensation [1]
Patellofemoral pain can result from deterioration of cartilage under the patella following intense periods of physical activity [7], while high medial compartment knee loading has been linked to increased medial compartment knee osteoarthritis progression in patients already with the disease [8, 9]
This study assessed the effects of different body-borne load distributions, load magnitudes, and walking speeds on tibiofemoral contact forces in soldiers while they walked
Summary
Lower-limb musculoskeletal injuries (MSI) reduce soldier capability and impose substantial costs on the person and military, i.e., rehabilitation and salary compensation [1]. Knee injuries are problematic, causing short-term impairment but often resulting in chronic degenerative diseases, such as knee osteoarthritis, requiring lifelong remuneration [2, 3]. The repetitive loading results in stress concentrations which are influenced by the complex interaction of anthropometric factors, distribution of external (e.g., ground reaction) and internal (e.g., muscle) forces acting about the site, as well as the state of the tissue (i.e., morphology and material properties) [6]. Patellofemoral pain can result from deterioration of cartilage under the patella following intense periods of physical activity [7], while high medial compartment knee loading has been linked to increased medial compartment knee osteoarthritis progression in patients already with the disease [8, 9]. Characterizing internal loads related to the development of MSI during commonly performed military tasks (e.g., load carriage) may help identify the mechanisms of common lower-limb MSI
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
