Isokinetic strength of fully operational U.S. Navy Seals with a previous history of shoulder and knee injury

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© 2016 - IOS Press and the authors. All rights reserved.BACKGROUND: Unintentional musculoskeletal injury has a significant impact on military personnel which is amplified in U.S. Navy Sea, Air, and Land Operators who participate in year round physical and tactical training. Full recovery from injury including restoration of strength is necessary for safe participation in training and performance of missions. Inadequate recovery may predispose the Operator to risk of future injury. OBJECTIVE: The purpose of this study was to examine isokinetic knee and shoulder strength of previously injured Operators who had returned to full duty. METHODS: Two previously injured cohorts, a knee injury group (n = 46) and a shoulder injury group (n = 55), were created from a larger group of Operators (n = 305) who had undergone strength testing. A comparison cohort was also created from each injury group (knee injury control group (n = 77) and shoulder injury control group (n = 121). All participants underwent isokinetic strength testing of their group assigned joint. This included knee flexion/extension strength testing for the knee group and shoulder internal/external rotation strength testing for the shoulder group. Side-to-side comparisons were made within each injury group and to the control group (injured extremity to strongest extremity of the control group). Individual counts within the injured Operators with strength deficits greater than 10% in their injured extremity were also performed. RESULTS: No significant side-to-side or between group differences were observed for the knee injury group. No significant side-to-side or between group differences were observed except for shoulder external rotation strength which was significantly different between groups (p = 0.003). Side-to-side strength deficits greater than 10% were observed in 20 to 25% of the injured Operators. CONCLUSION: The group comparisons demonstrate the effectiveness of the military group's rehabilitation and performance training programs, but continued vigilance and tracking of injured individuals are necessary to insure full recovery and return to duty as a small number of each injured cohort did have strength deficits bilaterally.






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Sell, TC, NC Clark, JP Abt, M Lovalekar and SM Lephart (2016). Isokinetic strength of fully operational U.S. Navy Seals with a previous history of shoulder and knee injury. Isokinetics and Exercise Science, 24(4). pp. 349–356. 10.3233/IES-160637 Retrieved from

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Timothy Crawford Sell

Associate Consulting Professor in the Department of Orthopaedic Surgery

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