# Effects of Different Moments of Inertia on Neuromuscular Performance in Elite Female Soccer Players During Hip Extension Exercise to Prevent Hamstring Asymmetries and Injuries: A Cross-Sectional Study

## TL;DR

This study examines how different flywheel inertial loads affect neuromuscular performance in elite female soccer players during hip extension exercises to reduce hamstring injury risks.

## Contribution

The study provides new insights into how varying inertial loads influence eccentric strength and limb asymmetry in female athletes.

## Key findings

- Higher inertia significantly reduced peak and mean acceleration and speed during hip extensions.
- Eccentric peak power increased in the non-dominant limb with higher inertial loads.
- Eccentric-to-concentric ratios remained stable across both inertia conditions.

## Abstract

Background: High-intensity actions like accelerations and decelerations, often performed unilaterally, are crucial in elite female football but increase the risk of interlimb asymmetries and injury. Flywheel resistance training enhances eccentric strength, yet limited research has assessed how different inertial loads affect mechanical outputs in unilateral exercises. Purpose: This study investigated how two inertial loads (0.107 kg·m2 and 0.133 kg·m2) influence power, acceleration, speed, and asymmetry during unilateral hip extensions in elite female footballers. Methods: Eighteen professional players (27 ± 4 years, 59.9 ± 6.5 kg, 168.2 ± 6.3 cm, BMI 21.2 ± 1.8) completed unilateral hip extensions on a conical flywheel under both inertia conditions. A rotary encoder measured peak/average power, acceleration, speed, and eccentric-to-concentric (E:C) ratios. Bilateral asymmetries between dominant (DL) and non-dominant (NDL) limbs were assessed. Paired t-tests and Cohen’s d were used for analysis. Results: Higher inertia reduced peak and mean acceleration and speed (p < 0.001, d > 0.8). Eccentric peak power significantly increased in the NDL (p < 0.001, d = 3.952). E:C ratios remained stable. Conclusions: Greater inertial loads reduce movement velocity but increase eccentric output in the NDL, offering potential strategies to manage neuromuscular asymmetries in elite female football players.