title: Pre-menarcheal physical activity predicts post-menarcheal lean mass and core strength, but not fat mass.
abstract: OBJECTIVE
  Youth exercise is associated with improved body composition, but details regarding timing and persistence are limited. We examined pre- and circum-menarcheal organized physical activity exposure (PA) as a factor in development of early post-menarcheal lean mass, fat mass and muscle strength.
  
  
  METHODS
  Participants in a longitudinal study of musculoskeletal growth using dual energy X-ray absorptiometry (DXA) were included based on: 1) Whole body DXA scans: 0.5-1.5 years pre-menarche, 0.5-1.5 years post-menarche; 2) PA records for ⋝6 months preceding the first DXA (prePA) and for the inter-DXA interval (circumPA). Dominant arm grip strength and sit-ups tests coincided with DXA scans; PA, height and maturity were recorded semi-annually. Regressions correlated PA with lean mass/fat mass/strength, accounting for maturity, body size, and baseline values.
  
  
  RESULTS
  Seventy girls [baseline: 11.8 yrs (sd 1.0), follow-up: 13.9 years (sd 1.0)] demonstrated circum-menarcheal gains of 25-29% for lean and fat mass and 33% for grip strength. PREPA correlated with pre- and post-menarcheal lean mass, sit-ups and pre-menarcheal fat mass (p<0.05), but not grip strength. CIRCUMPA correlated with only post-menarcheal sub-head lean mass (p=0.03).
  
  
  CONCLUSIONS
  Lean mass and core strength at 1-year post-menarche were more strongly predicted by pre-menarcheal organized PA than by recent circum-menarcheal PA.
authors.affiliation: University of Wisconsin School of Medicine and Public Health, Madison, WI.
authors.forename: M A
authors.initials: MA
authors.lastname: Day
authors.forename: J N
authors.initials: JN
authors.lastname: Dowthwaite
authors.forename: P F
authors.initials: PF
authors.lastname: Rosenbaum
authors.forename: G G
authors.initials: GG
authors.lastname: Roedel
authors.forename: A A
authors.initials: AA
authors.lastname: Brocker
authors.forename: T A
authors.initials: TA
authors.lastname: Scerpella
mesh_terms: D015502:Absorptiometry, Photon; D000273:Adipose Tissue / Q000254:growth & development* / Q000502:physiology; D000293:Adolescent; D001823:Body Composition / Q000502:physiology*; D002648:Child; D005260:Female; D006801:Humans; D008137:Longitudinal Studies; D008572:Menarche; D009043:Motor Activity / Q000502:physiology*; D053580:Muscle Strength / Q000502:physiology*; D018482:Muscle, Skeletal / Q000254:growth & development* / Q000502:physiology