Biomechanical assessment of the kicking and non-kicking limb during forward leaning over the ball versus leaning backwards in female professional soccer players

BACKGROUND:
Women’s sports, including soccer, have experienced exponential growth in recent years. Kicking, a fundamental asymmetrical skill in soccer, involves various techniques used in both offensive and defensive scenarios to enable passing, maintain possession, and achieve scoring opportunities. Effective kicking relies more on skill than power, as skill level significantly influences performance in specific game situations.(1) The kinematic sequence of a kick is divided into five phases: preparation, backswing, leg cocking, acceleration, and follow-through. These phases are defined by six key events: heel strike, toe-off, peak hip extension, peak knee flexion, ball strike, and toe velocity inflection.(2) Research indicates that greater ball velocity improves scoring success. However, no studies have examined differences in ground reaction forces (GRF) when striking the ball while leaning forward versus leaning backward, highlighting a gap for further investigation.

AIM:
This study examined the phase differences in GRF between the kicking and non-kicking limbs when striking a football while leaning forward and backward.

METHODS:
Twelve female professional Celtic FC Footballers (age: 22.8±4years; mass: 62.9±7.1kg) participated in a kicking biomechanical study. A 10-camera 3D Vicon motion analyses system integrated with 4 Kistler Force Plates were used. The task involved examining the kicking and non-kicking limb whilst forward leaning over the ball versus leaning backwards. The forward leaning kick mimicked a shot at goal while the backward leaning kick mimicked a clearance shot. Data was categorised into offensive and defensive player groups. Descriptive statistics for the Peak GRF of the Support Leg and Peak GRF of the Foot on Impact with the ball were reported with respect to player position, limb, and lean.

RESULTS:
With respect to player position, the Peak GRF of the Support leg were 1836.42±382.27N (95% CI [1688.19,1984.65] and 1741.81±339.17N (95% CI [1583.08,1900.55]) for the defensive and offensive players respectively. Peak GRF of the Foot on Impact with the ball were 24.07±20.30N (95% CI [16.20,31.94]) and 25.76±14.90N (95% CI [18.78,32.73]) for the defensive and offensive players respectively. Peak GRF was higher for the right limb and backward lean compared to the left limb and forward lean, respectively.

CONCLUSION:
The results provide valuable insights for professional female footballers, both defensive and offensive, regarding GRF during forward and backward leaning motions, involving both the kicking and non-kicking limbs.