Compensatory Strategies Persist In Special Operations Forces Personnel With A Previous Lower Extremity Injury

United States Special Operations Forces (SOF) personnel experience higher risk of musculoskeletal (MSK) injuries due to the rigorous nature of their training. Compensatory strategies may persist when returning to duty following an injury, increasing risk of future injury. PURPOSE: Assess limb symmetry and performance of SOF personnel with lower extremity injury history. METHODS: 15 SOF personnel who were cleared for unrestricted duty and reported a unilateral, lower extremity injury within 18 months of testing underwent a functional performance assessment (vertical jump (VJ), single limb vertical jump (SLJ), isometric mid-thigh pull (IMTP)) on bilateral force plates and completed a running mechanics evaluation using a markerless motion capture system. Paired-samples t-tests (α = 0.05) with Hedges’ g effect sizes were used to determine limb differences. RESULTS: The non-injured limb exhibited greater VJ peak concentric force (4.5%, p = 0.019, g = 0.645) and peak landing force (20.8%, p = 0.002, g = 0.943), greater SLJ height (14.0%, p = 0.023, g = 0.623), and greater vertical impulse during running (6.8%, p = 0.005, g = 0.818). No significant differences were found during the IMTP. CONCLUSION: Following injury, SOF personnel exhibit asymmetries favoring the non-injured limb during dynamic tasks. Cumulative effects of these loading avoidance strategies seen in running and jumping tasks may increase the risk of future overuse injury of the non-injured limb. Bilateral performance assessments alone may be ineffective at identifying persisting deficits of the injured limb. SLJ height differed between limbs, but compared to a non-injured cohort, study participants achieved similar VJ heights and IMTP forces. VJ heights were achieved with asymmetric take-off and landing forces, suggesting altered strategies that are likely representative of residual effects from injury. Current military rehabilitation programs may benefit from including unilateral performance assessments and/or evaluations of biomechanical characteristics during bilateral tasks. DISCLAIMER: The content is solely the responsibility of the authors and does not necessarily represent the official views of the Office of Naval Research, the US Navy, or the US Special Operations Command. Supported by the Office of Naval Research N0004-21-1-2682