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.
InjuryAny physical complaint sustained by a player that resulted from a football match or football training and led to the player being unable to take full part in future football training or match play.
Hip and groin injuryInjury located to the hip joint or surrounding soft tissues or at the junction between the anteromedial part of the thigh, including the proximal part of the adductor muscle bellies, and the lower abdomen.
ReinjuryInjury of the same type and location as a previous injury that occurred within 2 months of a player’s return to full participation.
Slight/minimal injuryInjury causing 0–3 days lay-off.
Mild injuryInjury causing 4–7 days lay-off.
Moderate injuryInjury causing 8–28 lay-off.
Severe injuryInjury causing >28 days lay-off.
Acute injuryInjury with sudden onset and known event.
Overuse injuryInjury with insidious onset and no identifiable event.
Injury rateNumber of injuries per 1000 player hours ((Σ injuries/Σ exposure hours)×1000).
Injury burdenNumber of lay-off days per 1000 player hours ((Σ lay-off days/Σ exposure hours)×1000)