Table 1 Study quality score key.

Study reference:	Score
How was allocation to the intervention group done?
2  =  random
1  =  cluster random
0  =  historical comparison/volunteer or convenience group
Was the assigned intervention concealed before allocation?
2  = adequate
1  =  unclear
0  =  inadequate/impossible
Were the outcomes of participants who withdrew described and included in the analysis (intention to treat/effect of compliance)?
2  =  withdrawals well described and accounted for in analysis
1  =  withdrawals described and analysis not possible
0  =  no mention, inadequate mention, or obvious differences and no adjustment
Were the outcome assessors blinded to treatment status?
2  =  effective action taken to blind assessors
1  =  small or moderate chance of unblinding of assessors
0  =  not mentioned or not possible
Were the inclusion and exclusion criteria (age, previous injury, sport) clearly defined?
2  =  clearly defined
1  =  inadequately defined
0  =  not defined
Were the intervention and control group comparable at entry?
2  =  good comparability of groups, or confounding adjusted for in analysis
1  =  confounding small; mentioned but not adjusted for
0  =  large potential for confounding, or not discussed
Were the interventions clearly defined?
2  =  clearly defined interventions are applied
1  =  clearly defined interventions are applied but the application is not standardised
0  =  intervention and/or application are poorly or not defined
Were the outcome measures used clearly defined? (injury: self‐reported injury/medically confirmed/severity defined)
2  =  clearly defined
1  =  adequately defined/recorded
0  =  not adequately defined/recorded
Was the surveillance period active and of clinically appropriate duration?
2  =  active surveillance and appropriate duration
1  =  active surveillance, but inadequate duration
0  =  surveillance not active or not defined
Total score (18  =  100%)