Table 1

Operational definitions

InjuryInjury resulting from playing football and leading to a player being unable to fully participate in future training and match play (ie, time-loss injury)
Muscle injuryIndirect or direct injury to the muscle leading to a player being unable to fully participate in training or match play
Return to playFull participation in training and availability for match selection
Indirect muscle injuryA muscle injury caused without the influence of a direct external trauma
 Functional muscle injuryPainful muscle injury/disorder (acute or chronic) without macroscopic evidence of muscle fibre damage (seen in ultrasound/MRI)
 Structural muscle injuryAny acute indirect muscle injury with macroscopic evidence of muscle fibre damage (seen in ultrasound/MRI)
Direct muscle injuryA traumatic muscle injury caused by a direct (blunt or sharp) external trauma
ContusionTissue bruise without concomitant injuries classified elsewhere
Muscle contusionDirect muscle trauma, caused by blunt external force
LacerationDirect trauma including skin and subcutaneous tissue, caused by sharp external force
Foul playViolation of the laws of the game according to the match referee
Lay-off/absenceNumber of days until the player resumed full team training
Re-injury/recurrencyInjury of the same type and at the same site as an index injury occurring no more than 2 months after a player's return to full participation from the index injury