Operational definitions used in the study
| Training session | Team training that involved physical activity under the supervision of the coaching staff |
| Match | Competitive or friendly match against another team |
| Injury | Any physical complaint sustained by a player that resulted from a football match or football training and led to the player being unable to take a full part in future football training or match play |
| Slight/minimal injury | Injury causing 0–3 days lay off |
| Mild injury | Injury causing 4–7 days lay off |
| Moderate injury | Injury causing 8–28 days lay off |
| Severe injury | Injury causing >28 days lay off |
| Traumatic injury | Injury with sudden onset and known cause |
| Overuse injury | Injury with insidious onset and no known trauma |
| Hamstring injury | A traumatic distraction or overuse injury to the hamstring muscle group (the musculotendinous complex of biceps femoris, semitendinosus and semimembranosus) |
| Reinjury | Injury of the same type and at the same site as an index injury occurring within 2 months after return to full participation from the index injury (ie, early recurrent injury) |
| Injury prevalence | The proportion of players affected by at least one injury during a season |
| Injury rate | Number of injuries per 1000 player-hours ((Σ injuries/Σ exposure-hours)×1000) |
| Injury burden | Number of lay off days per 1000 player-hours ((Σ lay off days/Σ exposure-hours)×1000) |