Table 7.

Results concerning sleep and injuries.

Study	Aim	Results	Findings
Chamari et al., [48]	To examine the effects over two consecutive years of the holy month of Ramadan on injury rates of a Tunisian top-level professional soccer team.	No significant differences between the three periods were observed for weekly mean training load, training strain, training duration, and Hooper’s Index (quality of sleep, and quantities of stress, delayed-onset muscle soreness, and fatigue). No significant difference in injury rates was observed between fasting and non-fasting players. Nevertheless, the rates of non-contact (6.8 vs. 0.6 and 1.1) and training overuse (5.6 vs. 0.6 and 0.5) injuries were significantly higher in RF than before or after Ramadan month.	Ramadan along with the corresponding changes in nutritional habits, sleeping schedule, and socio-cultural and religious events, significantly increased overuse and non-contact injuries in fasting players despite the fact that the training load, strain, and duration were maintained.
Gouttebarge et al., [29]	To explore the associations of severe musculoskeletal injuries (joint and muscles) and surgeries with symptoms of common mental disorders (distress, anxiety/ depression, sleeping disturbance, adverse alcohol behavior, smoking, adverse nutrition behavior) among male European professional soccer players.	Professional soccer players who had sustained three or more severe musculoskeletal injuries during their career were more than two times more likely to report sleeping disturbance (OR 2.3 and 95% CI 1.2–4.4) than professional soccer players who had not suffered from severe musculoskeletal injuries during their career. Professional soccer players who had sustained one or more severe joint injuries during their career were three to nearly four times more likely to report sleeping disturbance (OR 3.4 and 95% CI 1.9–6.2) than professional soccer players who had not suffered from severe joint injuries during their career.	European professional soccer players were 10–25% more likely to report symptoms of sleeping disturbance by every additional severe (joint or muscle) injury.
Kiliç et al., [49]	To explore the interaction between severe musculoskeletal time-loss injuries and symptoms of common mental disorders in professional soccer players over a 12-month period.	Symptoms of common mental disorders at baseline were not associated with the risk of severe musculoskeletal time-loss injury during the 12-month follow-up period, with relative risk of 0.6 (0.3–1.0) for sleep disturbance.	No relationship was found between symptoms of common mental disorders and the onset of severe musculoskeletal time loss injuries.
Krutsch et al., [50]	To investigate the factors influencing injuries in amateur soccer.	A total of 21.1% injuries happened during small-field soccer tournaments. The injury incidence of male players during match exposure was 469 per 1000 h soccer and significantly higher than in female players 313 (p = 0.025). Male players reported less and inadequate sleep the night before the tournament (p < 0.001).	Small-field tournaments in soccer have a high injury incidence. Male players have a higher injury incidence than female players and show a lack of sleep in the night before the tournament and poor warm-up performance on match day.
Laux et al., [19]	To examine the contribution of stress and recovery variables as assessed with the Recovery-Stress Questionnaire for Athletes (RESTQ-Sport) to the risk of injury in professional soccer players.	Overall, 34 traumatic injuries and 10 overuse injuries occurred. The recovery-related scale Sleep Quality (OR 0.53, p = 0.010) significantly predicted injuries in the month after the assessment.	The recovery-related scale sleep quality was a significant predictor implying that a lack of sleep or non-refreshing sleep also increases injury risk. It is suggested that a lack of recovery and sleep and high stress as well as a feeling of muscle strain and impending injury precede the injury and predict its occurrence.
Levitch et al., [51]	To provide a novel examination of the modifying role of sleep on the relationship between repetitive head impacts exposure and neuropsychological function in collegiate soccer players.	This sample had a high level of exposure to RHI, with a median count of 469 headers/year and 39 headers/two weeks, and they reported high levels of sleep disturbances, with over 50% of participants meeting criteria for “poor quality” sleep. With reduced sleep duration, a high level of recent heading exposure was related to worse sustained attention. However, with greater hours of sleep duration, heading exposure was related to preserved neuropsychological outcome in sustained attention.	Sleep may serve as a risk or protective factor for soccer players following extensive exposure to head impacts.
Nédélec et al., [18]	To examine the link between sleep and injury occurrence in an elite male soccer player competing in French League 1 and Union of European soccer Associations matches.	Three injuries were reported over the study period. Sleep onset latency, both in the single night (117 ± 43 min) and in the week (78 ± 50 min) before injury occurrence, was longer than pre-season baseline values (18 ± 13 min; ES: 3.1 and 1.6, respectively). Similarly, sleep efficiency in the single night (73 ± 7%) and the week (75 ± 7%) before injury occurrence was lower than baseline (90 ± 3%; ES: 3.2 and 2.8, respectively).	Sleep onset latency and efficiency were altered on the night and in the week before injury occurrence.
Silva et al., [17]	To investigate the relationship between sleep quality and quantity and injuries in elite soccer players. A secondary aim was to compare sleep-wake variables and injury characteristics.	The results indicated a moderate negative correlation between sleep efficiency and particular injury characteristics, including absence time, injury severity, and number of injuries. The linear regression analysis indicated that 44% of the total variance in the number of injuries (number) that can be explained by sleep efficiency, 24% of the total variance in the absence time after injury (days) that can be explained by sleep efficiency, and 47% of the total variance in the injury severity that can be explained by sleep efficiency.	Soccer players who exhibit lower sleep quality or non-restorative sleep show associations with increased amount and severity of musculoskeletal injuries.

RPE: rated perceived exertion; s-RPE: session rated perceived exertion; HR: heart rate; TL: training load; RF: Ramadan Fasting; RHI: repetitive head impacts; CI: confidence interval; OR: odds ration; ES: effect size.