title: Effects of maturation on combined female muscle strength and ACL structural factors.
abstract: OBJECTIVE
  Relations between lower limb muscle strength and female ACL injury risk are well documented. How these relations combine with key ACL geometries however, is unknown. Identifying how these combined factors are impacted by maturation would benefit current risk screening and prevention efforts. This study compared hamstrings and quadriceps strength and ACL cross sectional area (CSA) indices across three maturation groups.
  
  
  METHODS
  Cross-sectional human experimental.
  
  
  METHODS
  MRI scans of the dominant knee were collected in 35 females stratified into early (9.7±0.8yrs), middle (12.9±1.7yrs), and late (14.8±0.6yrs) maturation groups. Hamstring and quadriceps muscle volumes and ACL CSA measures were obtained. Isokinetic strength data were quantified for dominant knee flexors and extensors. Peak hamstring and quadriceps concentric and eccentric strength per unit volume magnitudes (QCSPV, HCSPV, QESPV, HESPV) were determined. Metrics and select ratios were submitted to a one way ANOVA to determine the main effect of maturation.
  
  
  RESULTS
  Significant decreases occurred in HESPV (N/cm(3)) and ACL CSA (cm(2)/kgm), respectively, from early (0.188±0.023N/cm(3), 0.007±0.002cm(2)/kgm) to middle (0.157±0.029N/cm(3), 0.005±0.002cm(2)/kgm, p=0.034, p=0.029), and middle to late (0.132±0.031N/cm(3), 0.003±0.001cm(2)/kgm, p=0.044, p=0.018) maturation. A significant decrease in HESPV:QCSPV occurred between early (1.795±0.496) and middle (1.362±0.277, p=0.018) maturation.
  ACL CSA was significantly greater in late (37.26±13.35) compared to middle (25.81±9.17, p=0.021) maturation.
  
  
  CONCLUSIONS
  Key ratios between female knee quadriceps and hamstring strength and ACL size parameters, which may directly impact ACL injury risk, are substantially different among three maturation states. The results are potentially hazardous strength mismatches in mid-pubertal females, where a smaller (weaker) ACL may be unable to stabilize quadriceps dominated loading strategies.
authors.affiliation: Human Performance Innovation Laboratory, School of Kinesiology, University of Michigan, United States. Electronic address: stevepd@umich.edu.
authors.forename: S P
authors.initials: SP
authors.lastname: Davidson
authors.affiliation: Human Performance Innovation Laboratory, School of Kinesiology, University of Michigan, United States; Departments of Athletic Training and Movement Science, School of Kinesiology, University of Michigan, United States.
authors.forename: S G
authors.initials: SG
authors.lastname: McLean
mesh_terms: D000293:Adolescent; D000367:Age Factors; D000704:Analysis of Variance; D016118:Anterior Cruciate Ligament / Q000033:anatomy & histology / Q000502:physiology*; D000070598:Anterior Cruciate Ligament Injuries; D002648:Child; D003430:Cross-Sectional Studies; D005260:Female; D000070633:Hamstring Muscles / Q000033:anatomy & histology / Q000502:physiology*; D006801:Humans; D053580:Muscle Strength / Q000502:physiology*; D052097:Quadriceps Muscle / Q000033:anatomy & histology / Q000502:physiology*; D012307:Risk Factors; D055815:Young Adult
keywords: Ligaments; Lower extremity; Muscle strength; Risk factors