title: Electromechanical delay of the hamstrings during eccentric muscle actions in males and females: Implications for non-contact ACL injuries.
abstract: Sex differences in neuromuscular functioning has been proposed as one of the factors behind an increased relative risk of non-contact anterior cruciate ligament (ACL) injury in females. The aim of this study was to explore sex differences in electromechanical delay (EMD) of the hamstring muscles during eccentric muscle actions and during a range of movement velocities. This study recruited 110 participants (55 males, 55 females) and electromyography of the semitendinosus, semimembranosus and biceps femoris was determined during eccentric actions at 60, 120 and 240°/s. No significant sex differences were observed irrespective of muscle examined or movement velocity. Irrespective of sex EMD significantly increased with increasing movement velocity (P < 0.01). There was no significant difference in the EMD of the 3 muscles examined. Our findings suggest that during eccentric actions of the hamstrings that there are no sex differences, irrespective of movement velocity. This would suggest that other factors are probably responsible for the increased relative risk of non-contact ACL injury in females compared to males.
authors.affiliation: Exercise and Sport Research Centre, School of Sport and Exercise, University of Gloucestershire, UK. Electronic address: mdestecroix@glos.ac.uk.
authors.forename: Mark B A
authors.initials: MB
authors.lastname: De Ste Croix
authors.affiliation: Exercise and Sport Research Centre, School of Sport and Exercise, University of Gloucestershire, UK.
authors.forename: Youssif O
authors.initials: YO
authors.lastname: ElNagar
authors.affiliation: Wolverhampton Wanderers Football Club, Wolverhampton, UK.
authors.forename: John
authors.initials: J
authors.lastname: Iga
authors.affiliation: Exercise and Sport Research Centre, School of Sport and Exercise, University of Gloucestershire, UK.
authors.forename: David
authors.initials: D
authors.lastname: James
authors.affiliation: Sports Research Centre, Miguel Hernández University of Elche, Alicante, Spain; ISEN University Formation, Center affiliate to the University of Murcia, Murcia, Spain.
authors.forename: Francisco
authors.initials: F
authors.lastname: Ayala
mesh_terms: D000328:Adult; D000070598:Anterior Cruciate Ligament Injuries; D005260:Female; D006801:Humans; D007866:Leg / Q000502:physiology; D008297:Male; D009119:Muscle Contraction; D018482:Muscle, Skeletal / Q000502:physiology*; D011930:Reaction Time; D012737:Sex Factors
keywords: Eccentric; Electromechanical delay; Injury risk; Sex