Effect of Isometric Mid-Thigh Pull Asymmetry and Change of Direction Speed on Reactive Agility and in Young Football Players

Background: Reactive agility (RA) and change of direction speed (CODs) are fundamental abilities that determine performance effectiveness in football. Biomechanical and motor factors, such as lower limb strength, asymmetry, and speed, may influence the level of these abilities. Moreover, reactive agility is a complex ability and may be partially dependent on the level of CODs. Methods: This study aimed to identify the key motor abilities responsible for shaping reactive agility in young football players. The study involved 55 boys aged 15.63±1.56 years. The following tests were used: the isometric mid-thigh pull (IMTP) for strength assessment, a 30 m sprint test, the 505 change of direction test, and reactive agility tests with and without a ball, utilizing the Skillcourt system. Results: Isometric strength and sprint speed were significantly correlated with the results of the 505 test. However, asymmetry in lower limb strength did not cause statistically significant changes in the analyzed parameters. Reactive agility without the ball showed significant correlations with speed, change of direction performance, and isometric strength. In the case of reactive agility with the ball, significant correlations were observed primarily with change of direction performance and reactive agility without the ball. Additionally, stepwise regression models revealed significant models for the 50 Random Run without the ball, the Star Run Random without the ball, and the 50 Random Run with the ball. Conclusions: Asymmetry in the isometric lower limb strength does not significantly affect the level of reactive agility or the ability to quickly CODs. Similarly, asymmetry in directional changes during running did not significantly impact the level of reactive agility. However, it may still be a contributing factor to increased injury risk in young football players.