title: The effect of gender on force, muscle activity, and frontal plane knee alignment during maximum eccentric leg-press exercise.
abstract: OBJECTIVE
  To investigate for gender differences during eccentric leg-press exercise. Tears of the anterior cruciate ligament (ACL) are considered to be related to eccentric tasks, altered neuromuscular control (e.g., reduced co-contraction of hamstrings), and increased knee abduction (valgus alignment). Based on these observations and the fact that ACL tears are more common in women, it was hypothesized that men and women differ significantly with regard to key parameters of force, knee stabilization, and muscle activity when exposed to maximum eccentric leg extension.
  
  
  METHODS
  Thirteen women and thirteen men were matched for age and physical activity. They performed maximum isokinetic eccentric leg-pressing against footplates of varied stability. The latter was done because earlier studies had shown that perturbational test conditions might be relevant in respect of ACL injuries. Key parameters of force, frontal plane knee stabilization, and muscle recruitment of significant muscles crossing the knee were recorded.
  
  
  RESULTS
  The 'force stabilization deficit' (difference between maximum forces under normal and perturbed leg-pressing) did not differ significantly between genders. Likewise, parameters of muscle activity and frontal plane leg stabilization revealed no significant differences between men and women.
  
  
  CONCLUSIONS
  This study is novel, in that gender differences in parameters of force, muscle activity, and leg kinematic were investigated during functional conditions of eccentric leg-pressing. No gender differences were observed in the measured parameters. However, the conclusion should be viewed with caution because the findings concurred with, but also contrasted, previous research in this field.
  
  
  METHODS
  Diagnostic study, Level III.
authors.affiliation: Department of Orthopaedic Surgery, Innsbruck Medical University, Anichstrasse 35, 6020, Innsbruck, Austria. michael.liebensteiner@i-med.ac.at
authors.forename: Michael C
authors.initials: MC
authors.lastname: Liebensteiner
authors.forename: Hans-Peter
authors.initials: HP
authors.lastname: Platzer
authors.forename: Martin
authors.initials: M
authors.lastname: Burtscher
authors.forename: Friedrich
authors.initials: F
authors.lastname: Hanser
authors.forename: Christian
authors.initials: C
authors.lastname: Raschner
mesh_terms: D000328:Adult; D000070598:Anterior Cruciate Ligament Injuries; D015444:Exercise / Q000502:physiology*; D005260:Female; D006801:Humans; D007719:Knee Joint / Q000502:physiology*; D007866:Leg / Q000502:physiology*; D008297:Male; D009119:Muscle Contraction / Q000502:physiology; D018482:Muscle, Skeletal / Q000502:physiology*; D012421:Rupture; D012737:Sex Factors