Hip and Knee Bilateral Deficit Across Bilateral, Unilateral, and Split-Load Leg Press Conditions

Area of Science:

• Biomechanics
• Sports Science
• Human Movement Analysis

Background:

• Understanding limb strength symmetry is crucial for performance and injury prevention.
• Bilateral deficit and asymmetry are key metrics in assessing neuromuscular function.
• Previous research has explored these concepts, but comparisons across different leg press modalities are less common.

Purpose of the Study:

• To investigate bilateral strength asymmetry, asymmetry index, and deficit ratio during one-repetition maximum (1RM) leg press under bilateral, unilateral, and split-load conditions.
• To examine the associations between these leg press metrics and isokinetic knee and hip strength asymmetries.

Main Methods:

• 31 resistance-trained males performed 1RM leg press tests in bilateral, unilateral, and split-load conditions.
• Isokinetic knee flexion/extension and hip extension strength were assessed at 60°·s^-1.
• Repeated measures ANOVA and correlation analyses were used to compare conditions and examine relationships.

Main Results:

• Split-load leg press demonstrated a significantly higher bilateral deficit ratio (14.29%) compared to the bilateral condition (5.16%).
• Significant inter-limb differences were found in isokinetic knee flexion and extension, but not hip extension.
• Bilateral strength asymmetry varied across tasks, while the bilateral asymmetry index remained lower and did not differ significantly across leg press conditions.
• Knee flexion bilateral asymmetry index correlated with hamstring-to-quadriceps ratios and cross-limb flexor-extensor ratios.

Conclusions:

• Split-load leg press is a viable method for detecting lower limb bilateral deficits due to easily measurable deficit values.
• Unilateral leg press can be utilized to identify lateral strength imbalances, showing relationships with isokinetic strength of knee flexors and extensors.