Biomechanical Characteristics of the Support Leg During Side-Foot Kicking in Soccer Players With Chronic Ankle Instability

Abstract

Background: Chronic ankle instability (CAI) in soccer players can increase the risk of recurrent ankle varus sprains and damage the articular surface of the ankle joint, thus increasing the risk of osteoarthritis. It is important to understand the biomechanical characteristics of the support leg during kicking in soccer players with CAI. Purpose/Hypothesis: The purpose of this study was to clarify the kinematics of the kicking motion of soccer players with CAI. It was hypothesized that at the point before ball contact when the support leg makes flat-foot contact with the ground, soccer players with CAI will land with ankle inversion in the support leg during a side-foot kick compared with players without CAI. Study Design: Controlled laboratory study. Methods: The study cohort included 19 male college soccer players (mean age, 20.5 ± 0.9 years) with greater than 8 years of soccer experience who were recruited from August 2019 to March 2020. Of these athletes, 10 had CAI and 9 had no CAI in the support leg, as diagnosed according to the Cumberland Ankle Instability Tool. Kinematic data for the trunk, hip, knee, and foot of the support leg during a side-foot kick were obtained using a 3-dimensional, motion-analysis system. The Mann-Whitney U test or Student t test was selected to identify differences in variables between the CAI and non-CAI groups. Results: There were no significant differences in physical characteristics between the CAI and non-CAI groups. At the point when the support leg made flat-foot contact with the ground, the players with CAI had more eversion of the hindfoot with respect to the tibia (-28.3° ± 12.1° vs -13.9° ± 14.2°; P = .03), a more varus alignment of the knee (26.0° ± 10.7° vs 13.7° ± 10.5°; P = .03), and a lower arch height index (0.210 ± 0.161 vs 0.233 ± 0.214; P = .046) compared with non-CAI players. Conclusion: Significant differences between players with and without CAI were seen in the support leg kinematics at flat-foot contact with the ground during the kicking cycle. Clinical Relevance: The biomechanical alignment of the support leg during a side-foot kick in players with CAI may reflect a subconscious attempt to avoid inversion of the foot and further ankle sprains.

Leg and Joint Stiffness of the Supporting Leg during Side-Foot Kicking in Soccer Players with Chronic Ankle Instability

“…Although the kicking motion was in the sagittal plane, the results of this study represented affected knee stiffness in the frontal plane. In a previous biomechanical study, the medial and lateral GRF components were generated in the supporting leg during the kicking cycle [17]. In addition, players with CAI had greater knee varus and hindfoot eversion angles at the flat-foot contact point [17].…”

“…A three-dimensional motion analysis system (Vicon MX system, Oxford Metrics, Oxford, UK) and AMTI force plates with an amplifier (MSA-6 Mini Amp, AMTI, Watertown, MA, USA) were used to measure the kinetic data and GRF during testing, according to a previous study [17]. The sampling rate was set to 250 Hz for the three-dimensional motion analysis system and to 1000 Hz for the AMTI force plates.…”

“…Thirty-nine reflective markers (14 mm) were placed to create the coordinate systems of the head, torso, arm, pelvis, and leg segments, according to the Vicon Plug-in Gait full-body model (Oxford Metrics, Oxford, UK) [28]. Reflective markers were placed on the head (left/right front head and back head), the torso (7th cervical vertebrae, 10th thoracic vertebrae, clavicle, sternum, and right scapula), the upper arm and forearm (left/right acromion, upper arm, lateral epicondyle, forearm, radial styloid, ulnar styloid, and the head of the second metacarpal), the pelvis (left/right anterior superior iliac spine and posterior superior iliac spine), and the thigh and tibial segments (left/right lower lateral third of the thigh, lateral epicondyle, lower third of the shank, second metatarsal head, calcaneus) [17,28]. This segment model was used to create coordinate systems and to obtain the lower extremity kinematic and kinetic data.…”

“…Previous studies have suggested that CAI in soccer players is associated with poor dynamic balance of the supporting leg [8] and foot eversion during foot strikes [17], indicating potential difficulties in withstanding the impact during foot strike. However, individuals with CAI have greater knee stiffness during jump landings than those without, suggesting a possible compensatory mechanism for poor ankle joint stability and knee stiffness [21].…”

“…Successful side-foot kicking involves efficiently transferring energy from the supporting leg to the proximal-to-distal of the kicking-leg during the inside kick [14,15]. Recently, the supporting leg kinematics and kinetics of side-foot kicking have been noted as key factors in kicking performance and injury development [14,16,17]. A previous biomechanical study reported that the supporting leg generates a greater vertical ground reaction of 2.28 body weight during the initial heel strike in the instep kick [18].…”