Abstract
Background:
Lower extremity asymmetry has been shown to be associated with increased risk of anterior cruciate ligament injury. Return-to-sport screens commonly involve assessing the restoration of symmetrical strength and balance. Therefore, it is important to understand how these measures are related.
Hypothesis/Purpose:
To determine if relationships exist between the Lower Quarter Y-Balance Test (LQ-YBT) component scores, composite scores, and isokinetic knee strength in healthy, female athletes.
Methods:
Female adolescent athletes completed the LQ-YBT and isokinetic knee strength as a part of a comprehensive evaluation in competitive level athletes (Tegner activity scale≥7). LQ-YBT anterior, posteromedial, and posterolateral component scores for the each leg were normalized to leg length, and composite scores for each leg were calculated for each participant. Knee flexion/extension strength was collected at 120°/second using a Biodex System 4. Peak torque was normalized by body weight, and paired t-tests were used to compare legs (α<0.05). Spearman correlation coefficients were calculated to test whether any LQ-YBT measures were associated to knee strength.
Results:
A total of 106 participants (age 13.8±2.4 years; BMI 20.2±3.0) were tested, and all were right leg dominant. No differences were found between LQ-YBT right and left component (Table 1), or composite scores (right 97.9 vs left 98.2, p=0.29). Flexion and extension strength were significantly increased on the right side (p=0.02, <0.01 respectively). There were significant, weak to moderate correlations between all LQ-YBT scores (components and composite) versus knee flexion strength (r=0.26 to 0.40) (Table 2). Left knee extension strength was weakly correlated to left anterior and posteromedial component scores (r=0.24, 0.34 respectively), as well as the left composite score (r=0.29). Right knee extension strength was only correlated to the right posteromedial component score (r=0.21) and the right composite score (r=0.22).
Conclusion:
Weak to moderate relationships exist between both component and composite LQ-YBT scores and knee strength. The strongest correlations were found between the LQ-YBT composite scores and knee flexion strength. LQ-YBT composite scores were relatively high, indicating a low chance of injury while differences were seen in knee strength between legs. Future injury prevention programs would benefit from utilizing both tools as the Y-Balance test evaluates motor control and isokinetic strength identifies muscular imbalance, both of which are important in reducing future injury risk.
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