title: Musculoskeletal Asymmetry in Football Athletes: A Product of Limb Function over Time.
abstract: Asymmetrical loading patterns are commonplace in football sports. Our aim was to examine the influence of training age and limb function on lower-body musculoskeletal morphology.
  
  
  
  Fifty-five elite football athletes were stratified into less experienced (≤3 yr; n = 27) and more experienced (>3 yr; n = 28) groups by training age. All athletes underwent whole-body dual-energy x-ray absorptiometry scans and lower-body peripheral quantitative computed tomography tibial scans on the kicking and support limbs.
  
  
  
  Significant interactions between training age and limb function were evident across all skeletal parameters (F16, 91 = 0.182, P = 0.031, Wilks Λ = 0.969). Asymmetries between limbs were significantly larger in the more experienced players than the less experienced players for tibial mass (P ≤ 0.044, d ≥ 0.50), total cross-sectional area (P ≤ 0.039, d ≥ 0.53), and stress-strain indices (P ≤ 0.050, d ≥ 0.42). No significant asymmetry was evident for total volumetric density. More experienced players also exhibited greater lower-body tibial mass (P ≤ 0.001, d ≥ 1.22), volumetric density (P ≤ 0.009, d ≥ 0.79), cross-sectional area (P ≤ 0.387, d ≥ 0.21), stress-strain indices (P ≤ 0.012, d ≥ 0.69), fracture loads (P ≤ 0.018, d ≥ 0.57), and muscle mass and cross-sectional area (P ≤ 0.016, d ≥ 0.68) than less experienced players.
  
  
  
  Asymmetries were evident in athletes as a product of limb function over time. Chronic exposure to routine high-impact gravitational loads afforded to the support limb preferentially improved bone mass and structure (cross-sectional area and cortex thickness) as potent contributors to bone strength relative to the high-magnitude muscular loads predominantly afforded to the kicking limb.
authors.affiliation: 1Exercise Medicine Research Institute, Edith Cowan University, Perth, WA, AUSTRALIA; 2Fremantle Dockers Football Club, Perth, WA, AUSTRALIA; 3Centre for Exercise and Sport Science Research, Edith Cowan University, Perth, WA, AUSTRALIA; 4School of Health Science, University of Notre Dame, Perth, WA, AUSTRALIA; and 5School of Exercise and Nutrition Sciences, Deakin University, Melbourne, VIC, AUSTRALIA.
authors.forename: Nicolas H
authors.initials: NH
authors.lastname: Hart
authors.forename: Sophia
authors.initials: S
authors.lastname: Nimphius
authors.forename: Jason
authors.initials: J
authors.lastname: Weber
authors.forename: Tania
authors.initials: T
authors.lastname: Spiteri
authors.forename: Timo
authors.initials: T
authors.lastname: Rantalainen
authors.forename: Michael
authors.initials: M
authors.lastname: Dobbin
authors.forename: Robert U
authors.initials: RU
authors.lastname: Newton
mesh_terms: D015502:Absorptiometry, Photon; D000328:Adult; D000886:Anthropometry; D056352:Athletes; D015519:Bone Density; D000072226:Computed Tomography Angiography; D003430:Cross-Sectional Studies; D006801:Humans; D007866:Leg / Q000033:anatomy & histology*; D053580:Muscle Strength; D018482:Muscle, Skeletal / Q000033:anatomy & histology*; D012916:Soccer; D013977:Tibia / Q000033:anatomy & histology*; D055815:Young Adult