Differences in Running Biomechanics between Young, Healthy Men and Women Carrying Load

Introduction: During U.S. Army Basic Combat Training (BCT), the incidence of tibial stress fracture (SF) differs between men and women, with women having a fourfold greater injury risk than men. There is evidence to suggest that the different injury rates are, in part, due to sex-specific differences in running biomechanics, including lower-extremity joint kinematics and kinetics, which are not fully understood, particularly when running with external load.

Materials and

Methods: We investigated sex-specific differences in the kinematics and kinetics of running biomechanics as well as the tibial SF risk in young, healthy adults. Using individualized musculoskeletal and finite-element models of women (N = 20) and men (N = 21), we computed the joint mechanics and tibial strains for each participant as they ran on an instrumented treadmill at 3.0 m/s with loads of 0.0 kg, 11.3 kg, or 22.7 kg. Using a probabilistic risk-prediction model, we also estimated the tibial SF risk over 10 weeks of BCT, for each load condition [1].

Results, Conclusions, and Discussions: Across all load conditions, compared to men, women had a significantly smaller flexion angle at the trunk (16.9% to 24.6%) but a larger flexion angle at the ankle (14.0% to 14.7%). Under load-carriage conditions, women had a larger flexion angle at the hip (17.7% to 23.5%). In addition, women had a significantly smaller hip extension moment (11.8% to 20.0%) and ankle plantarflexion moment (10.2% to 14.3%), but larger joint reaction forces (JRFs) at the hip (16.1% to 22.0%), knee (9.1% to 14.2%), and ankle (8.2% to 12.9%). Consequently, we found that women had a greater increase in tibial strain and SF risk than men as load increased, indicating higher susceptibility to injuries. When load carriage increased from 0.0 kg to 22.7 kg, SF risk increased by about 250% in women but only 133% in men [1].

In conclusion, when running with no load, women and men displayed significantly different joint kinematics at the trunk, hip, and knee. While men tend to flex their trunk more during running, women tend to flex their hip more instead. Not surprisingly, we found that women had a significantly greater increase in lower-extremity JRFs and tibial SF risk than men as load increased. Our results provide quantitative evidence of sex-specific differences in the kinematics and kinetics of running biomechanics and offer the opportunity to gain insights into the etiology of lower-extremity musculoskeletal injuries and potentially create countermeasures to reduce the risk of these injuries.

Reference: 1. Rubio et al., Front. Bioeng. Biotechnol., 11(2023): 1250937.

Acknowledgements (Optional): Acknowledgements: This research was supported by the Military Operational Medicine Program Area Directorate of the United States Army Medical Research and Development Command (USAMRDC, Fort Detrick, MD). The Henry M. Jackson Foundation work was supported by the USAMRDC under Contract No. W81XWH20C0031. In addition, we acknowledge support from the Department of Defense High Performance Computing Modernization Program.

Disclaimer: The opinions and assertions contained herein are the private views of the authors and are not to be construed as official or as reflecting the views of the United States Army, the United Sates Department of Defense, or The Henry M. Jackson Foundation for the Advancement of Military Medicine, Inc. This abstract has been approved for public release with unlimited distribution.