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PURPOSE: Running-related injuries are most often single-sided and are partially attributed to lower limb movement and loading asymmetries.1 Gluteus Medius (GM) plays a significant role in lower limb alignment, especially in the frontal and transverse planes by its influence on the pelvis and the femur.2 Female runners are more prone to GM weakness which has been proposed to be a risk factor for overuse injuries.3 These strength deficits contribute to abnormal lower limb kinematics and kinetics during dynamic tasks like running and jumping.4 These changes include an increase in peak hip adduction angle (HA), hip internal rotation angle (HI), knee abduction moment (KA) and rearfoot eversion angle (RE).4 Symmetry Angle (SA) is a commonly-used, robust measure of determining symmetry.1 No study has evaluated the role of unilateral GM strength on interlimb asymmetry for HA, HI, KA and RE during running. We hypothesized that female runners with stronger GM would demonstrate decreased interlimb asymmetry for HI, HA, KA and RE during running. METHODS: Thirty healthy female recreational runners (Age: 35.40±10.52 yrs, Height: 1.66±0.06 m, Weight: 61.61±7.31 kg) running at least 10 km per week participated in this study. Isometric GM strength was measured using a handheld dynamometer for the right lower limb and participants were divided into two groups of stronger and weaker. 3D gait analysis was conducted as participants ran on an instrumented treadmill at 2.98 m/s. Peak HA, HI, KA and RE were generated for the bilateral lower extremities and interlimb asymmetry using SA was calculated for all variables. A Shapiro-Wilk test for normality was conducted and it showed that all variables were not normally distributed. Wilcoxon Two-Sample Test was performed to look at differences between the two groups for HA, HI, KA and RE. RESULTS: Female runners with weaker GM demonstrated significantly increased asymmetry for HA (18.80±24.11 vs 12.20±24.11 %, p=0.02), HI (18.47±24.11 vs 12.53±24.11 %, p=0.03), and KA (18.33±24.11 vs 12.67±24.11 %, p=0.04). For RE, the weaker group had greater asymmetry (16.13±24.11 vs 14.87±24.11 %, p=0.35), but the relationship was not significant. CONCLUSIONS: This study suggested that runners with weaker GM on one side exhibited increased interlimb asymmetry during running for certain kinematic and kinetic variables. Future studies should determine how unilateral and bilateral strength deficits contribute to interlimb asymmetry and running biomechanics in healthy and injured runners.
Biomechanics | Exercise Science | Other Kinesiology
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REFERENCES: 1. Zifchock et al. (2006). J Biomech Vol 39; p.2792-2797. 2. Verrelst R, et al. (2014). BJSM Vol. 48; p.1564–1569. 3. Niemuth PE et al. (2005). CJSM Vol. 15; p. 14-21. 4. Mucha et al. (2017). JSMS Vol. 20; p. 349-355. Other references on poster PDF.