Abstract
Fatigue is known to influence dynamic knee joint stability from a neuromuscular perspective, and electromechanical delay (EMD) plays an important role as the feedback activation mechanism that stabilizes the joint. The aim of this study was to investigate the influence of soccer-specific fatigue on EMD in U13-, U15-, and U17-year-old female soccer players. Thirty-six youth soccer players performed eccentric actions of the hamstrings in a prone position at 60, 120, and 180°/s before and after a soccer-specific fatigue trial. Surface electromyography was used to determine EMD from the semitendinosus, biceps femoris and gastrocnemius. A time × age × muscle × velocity repeated measures analysis of variance was used to explore the influence of fatigue on EMD. A significant main effect for time (P = 0.001) indicated that EMD was significantly longer post- compared with pre-fatigue (58.4% increase). A significant time × group interaction effect (P = 0.046) indicated EMD was significantly longer in the U13 age group compared with the U15 (P = 0.011) and U17 (P = 0.021) groups and greater post-fatigue. Soccer-specific fatigue compromised neuromuscular feedback mechanisms and the age-related effects may represent a more compliant muscle-tendon system in younger compared with older girls, increasing risk of injury.
Highlights
Anterior cruciate ligament (ACL) injury is a common and potentially traumatic sports related injury, presenting with substantial short- and long-term morbidities (Griffin et al 2005)
Post hoc analysis revealed that Electromechanical delay (EMD) was significantly longer in the U13 age group compared with the U15 (p = 0.011) and U17 (p = 0.021) groups and this difference was greater post fatigue
The current study indicates that soccer specific fatigue significantly increases the EMD post fatigue, compromising neuromuscular control required to stabilise the joint, in female youth soccer players
Summary
Anterior cruciate ligament (ACL) injury is a common and potentially traumatic sports related injury, presenting with substantial short- and long-term morbidities (Griffin et al 2005). ACL tears tend to occur during activities including sudden acceleration and deceleration, rapid changes of direction, jumping and landing tasks; where rapid and unanticipated movement responses of the medial and lateral hamstring muscles are necessary to stabilize the knee joint and successfully counteract the extreme load forces generated (McLean et al 2010; Smith et al 2012). During these movements numerous muscle actions occur with differing co-contraction strategies required to stabalise the joint. Considering this additional time lapse and the need to develop sufficient muscular tension rapidly enough to provide dynamic joint stability, EMD should be considered when evaluating muscular responses to an imposed perturbation or injurious stress (Shultz and Perrin, 1999)
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Published Version
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