Ethics approval was received from the Ethics Review Committee (Human Research), Macquarie University, Sydney, Australia (reference number: 5201100183). Rugby players gave written consent to participate in the study. The study design was informed by the consensus statement on injury definitions and data collection procedures for studies of injuries in rugby .
Study population and sample
A prospective cohort study was conducted during the 2012 rugby season. Participants were recruited pre-season (March 2012) from one Australian amateur rugby club located in Sydney’s northern suburbs. All participants were registered male amateur club players, aged 18 years and older.
At recruitment, participants completed a self-reported questionnaire and underwent a physical assessment. The questionnaire gathered information regarding participant’s age, playing experience, position of play and the SF-36v2 health-related quality of life survey. The physical assessment consisted of free-standing height (cm) and body mass (kg) measurements using a Seca digital column scale.
Injury was defined according to the Rugby Union consensus statement  as any physical complaint, which was caused by a transfer of energy that exceeded the body’s ability to maintain its structural and/or functional integrity, that was sustained by a player during a rugby match or rugby training, irrespective of the need for medical attention or time-loss from rugby activities. In this study, only injuries that occurred during competition matches were recorded. A recurrent injury is defined as an injury of the same type and at the same site as an index injury and which occurs after a player’s return to full participation from the index injury. Injury severity was reported as the total number of days that have elapsed from the date of injury to the date of the player’s return to full participation in team training or available for match selection and injuries were categorised as slight (0–1 day), minimal (2–3 days), mild (4–7 days), moderate (8–28 days) and severe (>28 days). Actual time-loss was determined by conducting in-person or telephone follow-up of injured athletes. Finally, a non-fatal catastrophic injury was defined as a brain or spinal cord injury that results in permanent (>12 months) severe functional disability.
Match injuries were recorded by trained research assistants who were aligned with the rugby club’s sports medicine personnel (a registered chiropractor). The research assistants attended all matches and tracked injured participants throughout the season.
Injury data were collected using the Injury Report Form for Rugby Union as outlined in the Rugby Union data collection consensus document . Player grade was recorded at time of injury. Players were graded from 1st to 4th, with first grade players considered the highest level of play. In addition, a separate age-restricted grade; less than 21 years (Colts) was also followed. The time within the match that injury occurred was recorded as 1st quarter, 2nd quarter, 3rd quarter, 4th quarter or extra time. The position of play at the time of the injury was recorded, as was the injured body part, side of body and type of injury. The diagnosis of injury as identified by the club’s sports medical personnel was coded according to the Orchard Sports Injury Classification System version 10.1 (OSICS-10.1) . Details regarding whether their injury was recurrent, was caused by either overuse (repetitive strain) or single trauma and the type of contact were recorded. Details pertaining to whether the injury was a result of a violation of the laws of the game were recorded. The season for this cohort began on the 14th April and ended on the 25th August 2012, consisting of 17 rounds of competition.
Individual participant match-exposures were recorded over the course of the season. Each match typically lasted 60 min and exposure logs for each member were kept to the nearest half game, match-exposures were used to calculate the total match-hour exposure (MHE) during the 2012 season. Training exposure and training injuries were not recorded.
Injury incidence rates (IIRs) per 1000 h of match exposure were calculated by dividing the number of recorded injuries by the number of hours of match-play, multiplied by 1000. Player health-related quality of life (physical component summary [PCS] scores and mental component summary [MCS] scores), and physical characteristics (height, weight and BMI) were stratified by age-group and position of play, and expressed as means with standard deviations. SF-36v2 norm-based scores were calculated using gender/age-group matched Australian population data from The South Australian Health Omnibus Survey (SAHOS), 2008 . PCS and MCS were calculated using Australian factor score coefficient weights . In norm-based scoring, each scale is scored to have the same average (50) and the same standard deviation (10), meaning each point equals one-tenth of a standard deviation .
Regarding injuries, sub-groups were compared by calculating rate ratios (RR) of two IIRs. Ninety-five percent confidence intervals (95 % CIs) were calculated using standard formulae for Poisson rates . The 95 % CIs for RRs were used to determine whether two rates or proportions differed significantly from one another, that is, two IIRs were deemed statistically different from one another if the 95 % CI for their RR did not include the number 1.
Poisson mixed-effects generalised linear modelling was also used to explore the multivariate relationships between IIRs and potential predictors as hypothesised a priori (age, participation years, playing position (forwards versus backs), BMI and SF-36v2 summary scores). The mixed-effects model used a random intercept for each athlete to account for the correlation induced by multiple observations of the same person. All analyses were performed using the statistical software R version 3.0.2 “(The R Foundation for Statistical Computing, Vienna, Austria).