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 symptom sustained by a player as a result of a football match or football training that led to the player being unable to take full part in future football training or match play |
| Hamstring injury | A traumatic distraction or overuse injury to the hamstring muscle group (the musculotendinous complex of biceps femoris, semitendinosus and semimembranosus) including both first-time and recurrent lesions |
| Rehabilitation | A player was considered injured until team medical staff allowed full participation in training and availability for match selection |
| Lay-off | Number of days until the player resumed full team training |
| Early recurrence | Injury of the same type and at the same site as an index injury occurring within 2 months of returning to full participation after the index injury |
| Slight/minimal injury | Injury causing 0–3 days absence |
| Mild injury | Injury causing 4–7 days absence |
| Moderate injury | Injury causing 8–28 days absence |
| Severe injury | Injury causing >28 days absence |
| Traumatic injury | Injury with sudden onset and known cause |
| Overuse injury | Injury with insidious onset and no known trauma |