How Do Tired Muscles Contribute to The Risk of ACL Injury?

Researchers looked at the effects of fatigue on muscle responsiveness in U13-, U15-, and U17-year-old female soccer players.  By measuring the time difference between muscle activation and muscular force production, they found that muscle responsiveness was lower both after a soccer workout (as compared to pre-workout measurements), and for younger girls (as compared to older girls). The authors concluded that their results may demonstrate “a more compliant muscle-tendon system in younger compared with older girls”, suggesting that the decreased muscle responsiveness measured may contribute to an increased risk of injury to the ACL when fatigued or when younger.