Quadriceps Strength Correlations and Biomechanical Differences During the Single-Leg Squat Test With Posterior Versus...

Area of Science:

• Biomechanics
• Orthopedics
• Sports Medicine

Background:

• The single-leg squat test (SLST) is used for performance assessment after anterior cruciate ligament reconstruction (ACLR).
• Nonstance limb positioning during the SLST influences test outcomes and biomechanics, necessitating standardization for reliable ACLR outcome comparisons.

Purpose of the Study:

• To determine how nonstance limb position during the SLST affects the correlation between peak knee flexion limb-symmetry index (LSI) and quadriceps strength LSI.
• To analyze the influence of nonstance limb position on lower extremity biomechanics during the SLST in athletes post-ACLR.

Main Methods:

• A biomechanical cohort study involving 66 athletes 5-7 months post-ACLR.
• Athletes were grouped into posterior standardization (PS) or neutral standardization (NS) based on nonstance limb position during the SLST.
• Correlations between peak knee flexion LSI and quadriceps strength LSI were examined, alongside lower extremity joint biomechanics analyses.

Main Results:

• Posterior standardization (PS) showed a medium correlation (R=0.37) between peak knee flexion LSI and quadriceps strength LSI, while neutral standardization (NS) showed a small correlation (R=0.27).
• Both groups exhibited significantly less peak knee flexion and knee moment contribution in the surgical limb.
• Surgical limb anterior center of pressure change was greater with NS, and nonsurgical limb ankle moment contribution was greater with PS.

Conclusions:

• Peak knee flexion LSI may be a more reliable indicator of quadriceps strength LSI during the SLST with PS compared to NS after ACLR.
• PS is recommended for knee-specific performance testing and as an exercise regression for horizontal hopping post-ACLR.
• NS may be more suitable as an exercise regression for vertical hopping post-ACLR.