Numerous studies have found links between sleep quality and or quantity and injury risk in athletes of various ages and levels. This has encouraged the development of novel sleep technologies and popularized the implementation of sleep-monitoring sports teams. However, one of the limitations of traditional research is the focus on mean data reporting from groups of subjects. While mean data is certainly useful to generalize results to a broad population, individual responses tend to get lost in the mix. For coaches and sports medicine practitioners, it is the outliers and individual responses that are most meaningful and interesting. This is because in high performance sports, there is considerable inter-individual variability in how athletes respond and adapt to training. For this reason, case-study research can be very useful for influencing practice.
A new case study published ahead of print in the Journal of Strength and Conditioning Research explored the association between markers of sleep quality the night before as well as the week leading up to an injury in an elite UEFA soccer player (7-year starter). Sleep was monitored nightly throughout 4 months of a competitive season via wrist actigraphy. In addition, the athlete rated perceived sleep quality and regularly reported potential causes of disturbed sleep to coaching staff. The athlete sustained three separate injuries during the observation period. On day 12 the athlete suffered a groin injury (sidelined for 13 days), on day 26 the athlete suffered a hamstring strain (sidelined for 10 days) and on day 115 the athlete suffered an ankle sprain (sidelined for 29 days).
The results showed that sleep onset latency (i.e., how long it took the athlete to fall asleep) the night before injury as well as the week leading up to the injury was significantly longer than baseline values obtained during the preseason (effect sizes = 3.1 and 1.6, respectively). Additionally, sleep efficiency (i.e., the ratio of the total time spent asleep compared to the total amount of time in bed) the night before injury as well as the week leading up to the injury was significantly lower than baseline values (effect sizes = 3.2 and 2.8, respectively). The athlete slept worse following night games due to late meals and post-match interviews. Other contributors of poor sleep were feelings of anxiousness about the next match and general soreness. The authors conclude that sleep quality was substantially worse than the athletes baseline sleep performance prior to injury occurrence. Thus, monitoring sleep quality and intervening when sleep quality deteriorates may be a useful strategy for reducing injury risk in athletes.
Nedelec, M. et al. Case study: sleep and injury in elite soccer. A mixed method approach. Journal of Strength and Conditioning Research. In press.