Influence Of Sex And Limb Dominance On Functional Performance Symmetry And Loading In Entry-level Marines

Limb symmetry index (LSI) is a common tool for evaluating functional performance. An LSI of ≥90% is a common target for musculoskeletal injury patients to achieve before returning to activity. PURPOSE: Evaluate LSI between sexes and determine the impact of limb dominance on loading in healthy, active U.S. Marines. METHODS: In total, 651 entry-level U.S. Marines with no current injuries (187F/464M, 19.9 ± 2.4y, limb dominance 59 L/592R, 4.8 ± 3.2 months of service) completed a single testing session. Limb dominance was defined as the preferred limb to kick a soccer ball. Participants completed five repetitions of bodyweight bilateral squats. Participants completed five repetitions of the Abalakov jump by vertically jumping as high as possible using a natural arm swing. Peak eccentric and concentric force (N) were recorded bilaterally on dual force plates for the squat and jump. Participants completed an isometric mid-thigh pull by standing atop force plates with their knees and hips flexed at approximately 40-50° and 35°, respectively. A bar was fixed at the midpoint between the hips and knees. Participants pulled up as hard and as fast as possible and held a maximal effort for 3-5 seconds for three repetitions. Peak vertical force (N) was recorded bilaterally. Force values were normalized to patient’s body mass (N/kg). LSI was calculated as nondominant limb/dominant limb*100%. Independent samples t tests determined significant differences in LSI force variables and sexes. Paired t tests evaluated significant differences in loading between dominant and nondominant limbs. RESULTS: There were no differences in LSI values between sexes (p > 0.05; Table 1). Participants loaded the dominant limb more than the nondominant limb (p < 0.001; Table 1). CONCLUSIONS: Sex does not appear to influence LSI performance; however, limb dominance may influence loading patterns in healthy individuals. Limb dominance may need to be considered when evaluating LSI in injured patients. Supported by: This work was funded by the Office of Naval Research (N00014-21-12892) under WU 62331.The study protocol was approved by the University of Kentucky Institutional Review Board (#62029). The views expressed are the authors and do not reflect the official policy or position of the Uniformed Services University, Department of Defense, Department of Veterans Affairs, or the U.S. Government.