Abstract
BackgroundMusculoskeletal injuries, such as stress fractures, are the single most important medical impediment to military readiness in the U.S. Army. While multiple studies have established race- and sex-based risks associated with a stress fracture, the role of certain physical characteristics, such as body size, on stress-fracture risk is less conclusive.MethodsIn this study, we investigated the effects of body size and load carriage on lower-extremity joint mechanics, tibial strain, and tibial stress-fracture risk in women. Using individualized musculoskeletal-finite-element-models of 21 women of short, medium, and tall statures (n = 7 in each group), we computed the joint mechanics and tibial strains while running on a treadmill at 3.0 m/s without and with a load of 11.3 or 22.7 kg. We also estimated the stress-fracture risk using a probabilistic model of bone damage, repair, and adaptation.ResultsUnder all load conditions, the peak plantarflexion moment for tall women was higher than those in short women (p < 0.05). However, regardless of the load condition, we did not observe differences in the strains and the stress-fracture risk between the stature groups. When compared to the no-load condition, a 22.7-kg load increased the peak hip extension and flexion moments for all stature groups (p < 0.05). However, when compared to the no-load condition, the 22.7-kg load increased the strains and the stress-fracture risk in short and medium women (p < 0.05), but not in tall women.ConclusionThese results show that women of different statures adjust their gait mechanisms differently when running with external load. This study can educate the development of new strategies to help reduce the risk of musculoskeletal injuries in women while running with external load.
Highlights
Musculoskeletal injuries, such as stress fractures, are the single most important medical impediment to military readiness in the U.S Army
We separately evaluated the effect of body size on joint kinematics and kinetics for each of the three load conditions
In this study, we developed individualized M/finite element (FE) models for 21 women of short (n = 7), medium (n = 7), and tall (n = 7) statures and analyzed the effects of body size and load carriage on the kinematics and kinetics of lower extremity joints, tibial strain, and likelihood of stress fracture when these women ran without a load or with a load of 11.3 or 22.7 kg
Summary
Musculoskeletal injuries, such as stress fractures, are the single most important medical impediment to military readiness in the U.S Army. While multiple studies have established race- and sex-based risks associated with a stress fracture, the role of certain physical characteristics, such as body size, on stress-fracture risk is less conclusive. Overuse musculoskeletal injuries, such as stress fracture, account for 70% of all injuries among military recruits and active Soldiers in the U.S Army [1]. Increased duration and frequency of training sessions as well as heavy load carriage can increase the risk of stress fracture [5]. Other studies have shown no association between incidence of stress fracture and body size [7, 11]
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