Association between back-leg-chest muscle strength and kicking speed in soccer players: an observational study

Several studies have been performed on soccer kicks and stressed the significance of strength/power and coordination between the agonist and antagonist muscles of the lower limb. Along with accuracy, speed is also an important factor in a successful kick. It is reported that trunk musculature, hip and knee extensors of the non-kicking extremity, and hip adductors of the kicking side have a role in increasing the foot velocity while kicking. Since muscles do not work in isolation while kicking and several muscle groups of the leg and trunk have been reported to have a role in high-speed kicks, therefore measuring the combined strength of the leg, trunk, and arm muscles will be an appropriate method to examine their association with the kicking speed. The aim of this study was to examine the association of the combined strength of the lower extremities, back, chest, and arm muscles with the kicking speed of soccer players.

Forty male soccer players (mean age 15.7 years) participated in the study. The back-leg-chest (BLC) dynamometer (Baseline, New York, NY, USA) and the mobile camera measured isometric muscle strength and kicking speed, respectively. The BLC dynamometer measured the isometric strength of the knee, hip, back extensors, and arm muscles. The kicking speed was measured by asking participants to kick a football in three directions - right, middle, and left - from 11 meters.

Significant (P<0.001) negative correlations of isometric strength of the back, leg, chest, and arm muscles and kicking speeds were found in all three directions. In all three correlations, Pearson's correlation coefficient was -0.989. Simple linear regression results showed that 97.8% (adjusted R²) of the variance observed in kicking speed (KS; RT), KS (MD), and KS (LT), was explained by the movement in BLC muscle strength values.

Kicking speeds in the right, middle, and left directions were negatively associated with the isometric strengths of the back, leg, chest, and arms muscles, measured using the BLC dynamometer, in participating soccer players.