Abstract
Objectives: This study investigated the performance variability between limb type (dominant versus non-dominant leg) with regard to time (over season with three categories: pre-, start- and end-season) of professional soccer players. Methods: A total of 88 out of 124 male soccer players aged 16-30 years were asked to perform the specific athletic tasks single leg squat (SLS) and single leg landing (SLL) during different times in a full sports season. These functional tasks were evaluated using outcome measures of coefficient of variation, including frontal plane projection angle (FPPA) and hip adduction angle (HAA). Results: No significant difference was observed across all events between the dominant and non-dominant leg of the participants between screening sessions over time, for both SLS and SLL functional activities, except for one event in both second-order coefficient of variation for FFPA (FPPA V2) and HAA in SLS (at the start of season, p =0.006). The variations in FPPA and HA are clinically irrelevant, as no statistically significant differences were observed between limb types (dominant versus non-dominant leg) between screening sessions over a season, thereby suggesting that the performance variability is fairly consistent over time. Conclusions: There is consistency across the sports season in the performance variability of SLS and SLL.
Highlights
Among athletes, evaluation of biomechanical tasks is an important assessment tool and is commonly used for appraising performances, and for rehabilitation on the field and in clinical practice [1,2,3]
Single leg squat (SLS) and single leg landing (SLL) are two important simple physical examination tests that are commonly utilized to identify abnormal frontal plane lower extremity kinematics, which could be associated with a large number of factors responsible for the lower limb injuries [4,5]
The present literature suggests that the highest incidence of Anterior cruciate ligament (ACL) injuries is observed among soccer players, followed by gymnasts, costing billions of dollars for treatment and rehabilitation and sometimes taking almost a year for the athlete to return to pre-injury levels [6]
Summary
Evaluation of biomechanical tasks is an important assessment tool and is commonly used for appraising performances, and for rehabilitation on the field and in clinical practice [1,2,3]. Using SLS and SLL as early screening tools for individuals at higher risk of ligament injury is crucial, as they are found to be associated with classical abnormal kinematics, including increased hip medial rotation and adduction, and medial tibial rotation resulting in medial knee displacement known as dynamic knee valgus [4,7,8,9,10,11,12] This suggests that while there are a number of studies to establish the performance of the tasks and their correlation to lower limb injuries, very few studies, to date, have examined the effects of performance variability on lower limb kinematics to explore their possible connection with lower limb injuries
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