title: Seasonal change in bone, muscle and fat in professional rugby league players and its relationship to injury: a cohort study.
abstract: OBJECTIVE
  To examine the anthropometric characteristics of an Australian National Rugby League team and identify the relationship to type and incidence of injuries sustained during a professional season. It was hypothesised that body composition would not change discernibly across a season and that injury would be negatively related to preseason bone and muscle mass.
  
  
  METHODS
  A repeated measure, prospective, observational, cohort study.
  
  
  METHODS
  Griffith University, Gold Coast, Australia.
  
  
  METHODS
  37 professional male Australian National Rugby League players, 24.3 (3.8) years of age were recruited for preseason 1 testing, of whom 25 were retested preseason 2.
  
  
  METHODS
  Primary outcome measures included biometrics; body composition (bone, muscle and fat mass; dual-energy x-ray absorptiometry; XR800, Norland Medical Systems, Inc); bone geometry and strength (peripheral quantitative CT; XCT 3000, Stratec); calcaneal broadband ultrasound attenuation (BUA; QUS-2, Quidel); diet and physical activity history. Secondary outcome measures included player injuries across a single playing season.
  
  
  RESULTS
  Lean mass decreased progressively throughout the season (pre=81.45(7.76) kg; post=79.89(6.72) kg; p≤0.05), while whole body (WB) bone mineral density (BMD) increased until mid-season (pre=1.235(0.087) g/cm(2); mid=1.296(0.093) g/cm(2); p≤0.001) then decreased thereafter (post=1.256(0.100); p≤0.001). Start-of-season WB BMD, fat and lean mass, weight and tibial mass measured at the 38% site predicted bone injury incidence, but no other relationship was observed between body composition and injury.
  
  
  CONCLUSIONS
  Significant anthropometric changes were observed in players across a professional rugby league season, including an overall loss of muscle and an initial increase, followed by a decrease in bone mass. Strong relationships between anthropometry and incidence of injury were not observed. Long-term tracking of large rugby league cohorts is indicated to obtain more injury data in order to examine anthropometric relationships with greater statistical power.
authors.affiliation: Centre for Musculoskeletal Research,  School of Rehabilitation Sciences, Griffith Health Institute, Griffith University, Gold Coast, Queensland,  Australia.
authors.forename: Erin C
authors.initials: EC
authors.lastname: Georgeson
authors.forename: Benjamin K
authors.initials: BK
authors.lastname: Weeks
authors.forename: Chris
authors.initials: C
authors.lastname: McLellan
authors.forename: Belinda R
authors.initials: BR
authors.lastname: Beck