Affiliations: Warrior Human Performance Research Laboratory, University of Pittsburgh, Pittsburgh, PA, USA
Correspondence:
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Corresponding author: Timothy C. Sell, Department of Orthopaedic Surgery, School of Medicine, Duke University, Director, Michael W. Krzyzewski Human Performance Laboratory (K-Lab), DUMC 102916, Durham, NC 27705, USA. Tel.: +1 919 684 1355; E-mail:timothy.sell@duke.edu
Abstract: 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.
