Box 1 Outcome measures and injury definitions

Primary outcomes

• Shoulder and knee injury—Reporting a score of ≥ 40 points for shoulder or knee problems with the OSTRC-O. The responses to each of the four questions in the OSTRC-O are given a value from 0 to 25, where 0 equals no problems and 25 equals the maximum level for each question

• Injury rate—the number of first-time shoulder or knee injury events during the study follow-up per 1,000 h of handball play

Secondary outcomes

• Time-loss shoulder and knee injury—Reporting at least reduced participation or inability to participate due to a shoulder or knee problem with the OSTRC-O

 Substantial shoulder and knee problems—Reporting at least a moderate reduction in training volume or performance due to a shoulder or knee problem with the OSTRC-O

• Any shoulder and knee problem—Reporting anything but “full participation without any shoulder/knee problem” with the OSTRC-O

• Weekly prevalence of substantial shoulder and knee problems—The number of players who reported a substantial shoulder or knee problem with the OSTRC-O in each group divided by the total number of player reports in the group each week

• Weekly prevalence of any shoulder and knee problems—The number of players who reported any shoulder or knee problem with the OSTRC-O in each group divided by the total number of player reports in the group each week

Definitions

• Acute injury—Injury with a sudden onset

• Gradual onset injury—Injury not reported as having an acute onset