Association of past 12-month sports injury history with hop limb symmetry index in physically active university students: a cross-sectional study of field-based functional asymmetry profiles.

BACKGROUND

Physically active university students are exposed to relatively high levels of sport and training, and unrecognized functional asymmetry may persist after sports injury. The hop limb symmetry index (hop LSI) is a feasible field-based assessment measure in university physical education and training settings and may help describe residual functional asymmetry at the group level and inform decisions about further functional monitoring.

OBJECTIVE

To examine whether past 12-month sports injury history is associated with lower hop LSI in physically active university students and to describe their lower-limb and trunk functional asymmetry profiles.

METHODS

This cross-sectional study included 263 physically active university students, including 202 participants without injury and 61 with injury. The primary exposure was past 12-month sports injury history, and the primary outcome was hop LSI. Hop LSI, the proportion of low LSI, ankle dorsiflexion asymmetry, Y-Balance Test (YBT) mean reach asymmetry, and side-bridge asymmetry were compared between groups. The primary analysis used ordinary least squares (OLS) linear regression with sequential adjustment for demographic characteristics, training exposure, activity background, low back pain, and functional asymmetry measures. Standard errors were estimated using cluster-robust standard errors based on class_id.

RESULTS

The injury group had lower hop LSI than the no-injury group (91.96 ± 3.63% vs. 94.88 ± 1.97%; mean difference = -2.92 percentage points, 95% confidence interval (CI): -3.89 to -1.96, p < 0.001). In supplementary threshold-based analyses, the injury group showed higher proportions of both moderate asymmetry (LSI < 92%, exploratory threshold) and marked asymmetry (LSI < 90%, conventional threshold) were 42.6% and 23.0% in the injury group and 7.9 and 2.0% in the no-injury group, respectively [odds ratio (OR) = 8.64 and 14.54]. The injury group also showed greater ankle dorsiflexion asymmetry (15.05% vs. 7.41%), YBT mean reach asymmetry (3.48 cm vs. 2.20 cm), and side-bridge asymmetry (12.82% vs. 9.80%). Regression analyses showed that past sports injury history was associated with lower hop LSI in the unadjusted model (β = -2.92, 95% CI: -3.74 to -2.11), the covariate-adjusted model (β = -3.13, 95% CI: -3.86 to -2.40), and the fully adjusted model further including functional asymmetry measures (β = -2.48, 95% CI: -3.29 to -1.66) (all p < 0.001). Findings remained consistent after excluding outliers and after additional adjustment for core_composite_z.

CONCLUSION

Past 12-month sports injury history was associated with lower hop LSI and greater functional asymmetry in physically active university students. Combining hop LSI with multidimensional functional asymmetry assessment may help characterize current residual functional asymmetry profiles and guide post-injury functional monitoring in university physical education and training settings. These findings are descriptive and should not be interpreted as evidence of individual injury prediction; longitudinal studies are needed to evaluate predictive validity.