Table 1

Operational definitions

Training sessionTeam training that involved physical activity under the supervision of the coaching staff
MatchCompetitive or friendly match against another team
InjuryInjury resulting from playing football and leading to a player being unable to fully participate in future training or match play (ie, time-loss injury)
Hamstring injuryA traumatic distraction or overuse injury to the hamstring muscle leading to a player being unable to fully participate in training or match play
RehabilitationA player was considered injured until team medical staff allowed full participation in training and availability for match selection
Lay-offNumber of days until the player resumed full team training
Re-injuryInjury 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
Minimal injuryInjury causing absence of 1–3 days from training and match play
Mild injuryInjury causing absence of 4–7 days from training and match play
Moderate injuryInjury causing absence of 8–28 days from training and match play
Severe injuryInjury causing absence of over 28 days from training and match play
Traumatic injuryInjury with sudden onset and known cause
Overuse injuryInjury with insidious onset and no known trauma