DOES ANTERIOR CRUCIATE LIGAMENT INJURY ALTER MUSCLE COACTIVATION STRATEGY AND KNEE EXCURSION IN ADOLESCENT FEMALES AND MALES?

During high-demanding tasks, the role of neuromuscular control becomes crucial in preventing anterior cruciate ligament injury (ACLi). The coactivation strategy stands as a critical element in neuromuscular control for dynamic stabilization, and its impact can be particularly pronounced in the presence of ACL injury (ACLi), especially among adolescents. Therefore, identifying how ACLi impact in the coactivation level in adolescents can enhance the clinical decision-making and rehabilitation process. We explored differences in muscle coactivation level in pediatric ACLi males and females compared with their uninjured counterparts. A total of 122 adolescent athletes (37 ACL females: 15.2(1.4) years old, 64.1(9.8) kg, 164.8(6.1) cm height; 39 uninjured females: 13.2(1.6) years old, 50.8(11.1) kg, 161.7(8.1) cm height; 17 ACL males: 15.4(1.2) years old, 69.4(16.1) kg, 174.5(9.5) cm height; 29 uninjured males: 13.2(1.7) years old, 51.7(13.1) kg, 164.4(13.9) cm height) performed bilateral drop vertical jumps. The first land of drop vertical jump was analyzed and was divided into 3 phases: preparatory (100ms prior to initial contact), deceleration (initial contact until peak knee flexion) and acceleration (peak knee flexion until take-off). Quadriceps to hamstrings (Q:H) lateral and medial coactivation indexes were estimated using the electromyography (EMG) of vastus lateralis and biceps femoris, and vastus medialis and semitendinosus, respectively. Knee excursion in frontal plane was estimated as maximal Euclidean distance of the knee joint center throughout each phase. Comparison of coactivation (lateral and medial) and knee excursion between ACL females and males with their uninjured counterparts were made using statistical parametric mapping for each drop vertical jump phase. ACLi females presented higher levels of both lateral (48-70%, p=0.010) and medial (0-100%, p ) ACLi females exhibited higher coactivation during the preparatory phase before initial contact. This may serve as a protective mechanism in preparation for the deceleration phase, that can lead to a stiffer landing. While ACL males increased coactivation at the onset of the deceleration phase, possibly to enhance landing absorption. This highlights distinct strategies employed by males and females to stabilize the knee during landing. In summary, ACLi patients require a higher level of neuromuscular control to maintain knee excursion.