By Charlie Fethney
It is widely accepted that a ‘good night’s sleep’ will elicit optimum performance in sport through both physiological and cognitive avenues (Halson, 2008). In Rugby (both Union and League), studies have documented the sleep patterns of elite players at different times of the year (Dunican, Walsh, et al., 2018; Eagles & Lovell, 2016; Shearer, Jones, Kilduff, & Cook, 2015; Thornton, Delaney, Duthie, & Dascombe, 2018).
How is sleep measured?
The gold standard is Polysomnography. This method measures brain activity, neuromuscular activity, respiration, blood oxygen saturation, heart rate, body position, and snoring (Dunican, Walsh, et al., 2018). This is usually done in controlled laboratory conditions, and can be expensive and logistically challenging.
A more commonly used measurement is actigraphy (Eagles & Lovell, 2016; Shearer et al., 2015; Thornton et al., 2018). An actigraph is a small watch-like device worn on the wrist or arm, and uses accelerometers to record body movements.
When measuring sleep, 3 attributes are measured: –
- Sleep duration – the onset of sleep to waking (measured in hours)
- Sleep efficiency – can either be calculated using algorithms built into the actigraph (Eagles & Lovell, 2016; Thornton et al., 2018), or by dividing the time spent asleep by the time spent in bed (multiplying by 100 to give a percentage) (Dunican, Walsh, et al., 2018; Shearer et al., 2015)
- Time awake after onset (or time awake) – how much time is spent in bed not asleep, after falling asleep (measured in minutes)
Sleep duration, sleep efficiency and time awake have been measured in 4 Rugby studies during the off-season, pre-season, and in-season (match and training days) (Dunican, Walsh, et al., 2018; Eagles & Lovell, 2016; Shearer et al., 2015; Thornton et al., 2018). Below, we compared the findings from these studies to the recommended guidelines set by the National Sleep Foundation (Hirshkowitz et al., 2015; Ohayon et al., 2017).
Interestingly, the night before a match players spent 9 hours in bed but only slept for 7.5 – recording a sleep efficiency of 78% and a time awake of 90 minutes after the onset of sleep (Shearer et al., 2015).
In one study, Dunican et al., (2018) investigated the following sleep disorders in 25 professional Super Rugby players using questionnaires and polysomnography during one night’s sleep in a sleep laboratory.
- Insomnia – inability to sleep/staying asleep too long/waking too early
- Excessive daytime sleepiness – likelihood of dozing or falling asleep in normal waking situations
- Obstructive Sleep Apnoea (OSA) – repeated partial or full closures of the upper airway during sleep
- Restless Leg Syndrome (RLS) – the need to continuously move the legs during waking hours
- Periodic Limb Movements (PLM) – repeated sudden movements of the limbs during sleep. A PLM index (PLMI) was calculated to give the number of leg movements per hour.
All players reported some symptoms of insomnia without the required levels to be clinically diagnosed. Also, each player reported excessive daytime sleepiness.
24% of players were found to have mild levels of OSA. Mild OSA is defined as more than five but less than fifteen airway closures per hour. OSA has been associated with increased daytime sleepiness which can lead to difficulty retaining information.
12% of players recorded a PLMI exceeding 15 movements per hour which is classified as a mild condition. Interestingly, players experiencing PLMs had no differences in duration or efficiency of sleep, nor OSA, compared to athletes without mild levels of PLMs.
Caffeine taken in the late afternoon, prior to an evening kick off, could be a contributing factor to late onset of sleep resulting in a short sleep duration (Eagles & Lovell, 2016). This suggestion is supported by Dunican(2018b), who found that consuming caffeine prior to evening Super Rugby matches reduced sleep duration and efficiency.
Post-game socialising and press commitments may decrease post-match sleep duration (Dunican, Higgins, et al., 2018). Related, alcohol consumption has been shown to reduce sleep quality (reduced sleep duration) (Halson, 2008).
Travel should also be considered when attempting to optimise sleep quality of professional athletes. For example, journey time after an evening match could delay sleep onset, thereby reducing sleep duration. With that said, sleep efficiency is less affected by short trips (including domestic flights) (Fowler, Duffield, & Vaile, 2015). Long distance international travel commitments however (common in a Super Rugby season), can disrupt sleep quality and induce fatigue (Fowler et al., 2015).
Team activities, such recovery sessions or travel, after match days could be postponed to the afternoon to allow for the recommended seven to nine hours of sleep (Hirshkowitz et al., 2015). For example, Dunican (2018b) reported players fell asleep later than 2am after a match and were expected to attend a team recovery session at 10h30am – resulting in less than five hours of sleep (Dunican, Higgins, et al., 2018).
Sleep duration, sleep efficiency, and time spent awake should be considered when designing team timetables to allow for optimal training adaptations and recovery from matches.
Dunican, I. C., Higgins, C. C., Jones, M. J., Clarke, M. W., Murray, K., Dawson, B., … Eastwood, P. R. (2018b). Caffeine use in a Super Rugby game and its relationship to post-game sleep. European Journal of Sport Science, 18(4), 513–523. https://doi.org/10.1080/17461391.2018.1433238
Dunican, I. C., Walsh, J., Higgins, C. C., Jones, M. J., Maddison, K., Caldwell, J. A., … Eastwood, P. R. (2018). Prevalence of sleep disorders and sleep problems in an elite super rugby union team. Journal of Sports Sciences, 1–8. https://doi.org/10.1080/02640414.2018.1537092
Eagles, A., & Lovell, D. (2016). Changes in sleep quantity and efficiency in professional rugby union players during home based training and match-play. J Sports Med Phys Fitness, (56), 565–571. Retrieved from http://www.ncbi.nlm.nih.gov/pubmed/25369280
Fowler, P., Duffield, R., & Vaile, J. (2015). Effects of simulated domestic and international air travel on sleep, performance, and recovery for team sports. Scandinavian Journal of Medicine and Science in Sports, 25(3), 441–451. https://doi.org/10.1111/sms.12227
Halson, S. L. (2008). Nutrition, sleep and recovery. European Journal of Sport Science, 8(2), 119–126. https://doi.org/10.1080/17461390801954794
Hirshkowitz, M., Whiton, K., Albert, S. M., Alessi, C., Bruni, O., DonCarlos, L., … Adams Hillard, P. J. (2015). National sleep foundation’s sleep time duration recommendations: Methodology and results summary. Sleep Health, 1(1), 40–43. https://doi.org/10.1016/j.sleh.2014.12.010
Ohayon, M., Wickwire, E. M., Hirshkowitz, M., Albert, S. M., Avidan, A., Daly, F. J., … Vitiello, M. V. (2017). National Sleep Foundation’s sleep quality recommendations: first report. Sleep Health, 3(1), 6–19. https://doi.org/10.1016/j.sleh.2016.11.006
Shearer, D. A., Jones, R. M., Kilduff, L. P., & Cook, C. J. (2015). Effects of competition on the sleep patterns of elite rugby union players. European Journal of Sport Science, 15(8), 681–686. https://doi.org/10.1080/17461391.2015.1053419
Thornton, H. R., Delaney, J. A., Duthie, G. M., & Dascombe, B. J. (2018). Effects of preseason training on the sleep characteristics of professional rugby league players. International Journal of Sports Physiology and Performance, 13(2), 176–182. https://doi.org/10.1123/ijspp.2017-0119
Charlie Fethney is a BSc Sport and Exercise Medical Sciences student at the University of Exeter (UK). He is currently completing a research internship at the University of Cape Town (South Africa). His current research interests are concussion, sport injury prevention and rehabilitation. Charlie also plays rugby for the University of Exeter.
In February 2015, we posted an article “Research in Rugby growing exponentially-Rugby Research’s Top 15” https://rugbyscientists.com/2015/02/20/research-in-rugby-growing-exponentially-rugby-researchs-top-15/. Based on a Scopus search (scopus.com) at the time (February 2015), we illustrated the growth of rugby research and the top rugby researchers and rugby research institutions. Here is the 3-year update (April 2018).
Before we get into the results, these are the search terms we entered into Scopus. For those unfamiliar with Scopus, it’s a database of peer-reviewed published research. Like any search database, you in type in a search term and it retrieves all the relevant data.
Below are our search terms: –
“Rugby” (will include rugby union, rugby league, rugby, etc)
“Rugby Union” (only rugby union)
My research interest is the tackle in rugby, so I also searched for: –
“Rugby” AND “Tackle”
“Rugby Union” AND “Tackle”
Only research with the above terms in the title, abstract or keywords were retrieved. The search includes all subject areas.
We report the number of articles by year, the top 15 rugby researchers, the top 15 rugby publishing journals, and the top 15 rugby research institutions.
Articles by year for “Rugby”
5031 articles on “rugby” since 1847.
3150 (63%) articles produced in the last 10 years. Average of 315 articles a year. 1338 published since the 2015 post.
Top 15 “Rugby” Publishing Journals
Top 15 “Rugby” Researchers
Articles by year for “Rugby Union”
1157 “Rugby Union”articles.
864 (75%) over the last 10 years. That’s an average of 86 articles a year. 391 published articles since 2015.
Top 15 “Rugby Union” Publishing Journals
Top 15 “Rugby Union” Researchers
Top 15 “Rugby Union” Research Institutions
Articles by year for “Rugby” AND “Tackle”
Top 15 “Rugby” AND “Tackle” Researchers
Top 15 “Rugby” AND “Tackle” Research Institutions
Articles by year for “Rugby Union” AND “Tackle”
Top 15 “Rugby Union” AND “Tackle” Publishing Journals
Top 15 “Rugby Union” AND “Tackle” Researchers
Top 15 “Rugby Union” AND “Tackle” Institutions
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