Differences in Kinematic and Muscle Activity Between ACL Injury Risk and Healthy Players in Female Football: Influence of Change of Direction Amplitude in a Cross-Sectional Case-Control Study

Abstract

Background and Objectives: Anterior cruciate ligament (ACL) injury rates remain high and have a significant impact on female football players. This study aims to evaluate knee kinematics and lower limb muscle activity in players at risk of ACL injury compared to healthy players through three side-cutting tests. It also investigates how the amplitude of a change in direction influences stabilization parameters. Materials and Methods: A cross-sectional case-control study was conducted with 16 second division female futsal players (23.93 ± 5.16 years), divided into injured (n = 8) and healthy groups (n = 8). Injured players had a history of non-contact knee injury involving valgus collapse, without undergoing surgical intervention. Three change of direction tests, namely the Change of Direction and Acceleration Test (CODAT), Go Back (GOB) test, and Turn (TURN) test, were used for evaluation. The peak and range of knee joint angles and angular velocities across three planes, along with the average rectified and peak envelope EMG signals of the Biceps Femoris (BF), Semitendinosus (ST), Vastus Medialis (VM), and Lateral Gastrocnemius (LG), were recorded during the preparation and load phases. Group differences were analyzed using two-factor mixed-model ANOVA with pairwise comparisons. Statistical significance was set at p < 0.05. Results: Injured players demonstrated lower external tibial rotation angular velocity and a greater range of motion in tibial external rotation compared to healthy players. Additionally, the injured group showed significantly higher average rectified muscle activity in VM and LG both increased by 4% during the load phase. The CODAT and TURN tests elicited higher BF and VM muscle activity, compared to the GOB test. The TURN test also showed greater extension angular velocity in the sagittal plane. Conclusions: The results revealed differences in knee kinematics and muscle activity between players at risk of ACL injury and healthy players, influenced by the amplitude of directional changes. Players altered transverse plane mechanics and increased VM and LG activation during LOAD may reflect a dysfunctional motor pattern, while the greater sagittal plane angular velocity and VM and BF activation from the CODAT and the TURN test highlight their higher potential to replicate ACL injury mechanisms compared to the GOB test.

Keywords: anterior cruciate ligament; biomechanics; electromyography; female football; injury prevention.

Figure 1

Functional change of direction test: CODAT, GOB test, and TURN test. Starting position is indicated with the dark circle and the cross identifies the change of direction task that was recorded. (A) Change of Direction and Acceleration Test (CODAT)—this test combines sprinting mechanics with the stabilization and acceleration required for change of direction movements. It consists of four diagonal change of direction tasks: two at 45° and two at 90°, interspersed with 3 m sprints and culminating in a 10 m sprint. (B) Go and Back (GOB) test—this test involves a 10 m frontal sprint at maximum possible speed, followed by deceleration and a final backward sprint. It simultaneously incorporates a change of direction and a deceleration task, both of which are common mechanisms associated with ACL injuries. (C) TURN test—this test is a modified version of the T-test. It involves a frontal sprint followed by a single pre-planned 90° change of direction, performed once in each direction.

Figure 2

Sagittal plane for angular velocity of TURN, GOB, and CODAT mean values during the LOAD phase.

Figure 3

Transverse plane for injured and healthy players based on mean player angular velocity data from functional tests (CODAT, GOB, and TURN) in the CODAT test during the LOAD phase.