Table 1

Operational definitions used in the study

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 participate fully in future training or match play (ie, time-loss injury)
RehabilitationA player was considered to be injured until team medical staff allowed full participation in training and availability for match selection
ReinjuryInjury 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
MCL injuryA traumatic injury to the superficial MCL, deep MCL and the posterior oblique ligament leading to a player being unable to participate fully in training or match play
Slight/minimal injuryInjury causing lay-off of 0–3 days from training and match play
Mild injuryInjury causing lay-off of 4–7 days from training and match play.
Moderate injuryInjury causing lay-off of 8–28 days from training and match play
Severe injuryInjury causing lay-off of more than 28 days from training and match play
Traumatic injuryInjury with sudden onset and known cause
Overuse injuryInjury with insidious onset and no known trauma
Non-contact injuryInjury occurring without contact with another player or object
Dominant legPreferred kicking leg
Foul playViolation of the laws of the game according to the match referee
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)
  • MCL, medial collateral ligament.