Exploring the Science Behind Resting Athletes
It seems not a week or even a day goes by without another sport story in the media on rest. In football, Jose Mourinho has bemoaned his team’s fixture congestion over Christmas and recently with the Europa League and domestic scheduling. Perhaps with a strong case considering Leicester City won the Premier League last season with only 43 games in their season and Champions-Elect Chelsea can only play a maximum of 47 this year (Manchester United would play 64 this season if they reach the Europa League final). With no European involvement and therefore less games, Leicester and Chelsea used the least number of different players in a squad in their respective successful seasons. With more “rest” time available within their season there is less need for rotation.
The sport with possibly the most intense speculation on this topic is the NBA. Always under the media spotlight, LeBron James recently told reporters “I’ll rest when I retire” but has since said that he is trusting his coach when it comes to the scheduling of rest games. Quite a stir has been caused in the NBA with teams resting players for games, supposedly to the detriment of the fans and the media, such as the primetime matchup between the Spurs and the Warriors. In response, the NBA has sent a memo to team owners urging them to be more involved in the decision making process. Apparently resting starters in some games has become “an extremely significant issue for our league” according to NBA Commissioner Adam Silver. There has certainly been an increase in the use of “DNP-Rest” (Did Not Play) in the last few seasons, as discussed here by Tom Haberstroh with ESPN. Haberstroh has gone on to argue that due to the frequency of DNP-Rest, the 82 game regular season has already been lost:
Sportsmen and women often have punishing travel and sleep schedules to contend with as well as the physical and mental demands of their specific sport. On top of this, although sometimes forgotten, are the “normal” stresses that we all have to contend with in life (career pressures, relationships, crying newborns, the school run etc.) Some of these athletes may be lucky to have access to more luxurious methods of travel and accommodation but that does not completely remove the associated fatigue of travel. So when we consider rest, it is not just the physical aspect of sport that we are trying to aid our athletes in recovering from.
Consequently, adjustments are being made in professional sport to try and combat this, with rest and reducing workload one intervention that is amassing a great deal of attention. Traditionally some sports may employ a short practice on the morning of an evening game – such as a shoot around in basketball, a morning skate in ice hockey or a pitcher’s stretch around lunchtime in baseball. Removing this session to help reduce workload and increase the focus on sleep and recovery has become a hotly debated topic this season in the NHL for example.
As Sports Scientists it is our responsibility to constantly revisit the science on topics such as these. Rest and recovery are pertinent areas in Sports Science and one that has already been mentioned on Sports Discovery. Previously Jonny discussed this in his post entitled ‘What precisely is the role of the Sports Scientist?’, in response to suggestions in the media that Sports Science is turning athletes ‘soft’. The increased understanding of the balance of training and rest, as well as greater awareness and availability of recovery strategies, have perhaps augmented our interventions in this area. Such interventions may be an attempt to maximise performance, minimise injury risk, prolong athlete careers, or perhaps a combination of all three reasons. The data to assess such outcomes remain to be seen but for now let’s explore some of the scientific basis behind rest and recovery.
The Science of Rest and Recovery
Rest and/or recovery have always been important components in training, underpinning theories of periodization and supercompensation. With the chance to rest after a training stimulus the body can, in theory, repair and regenerate itself and thus adapt to greater levels than the baseline. Conversely, a lack of sufficient recovery after training can proliferate the effects of fatigue and over time non-functional overreaching and overtraining syndrome may develop. These states are associated with a prolonged decrement in performance, immune suppression, sleep disturbances, and reduced self-perceptions and mood states. For more on overtraining, I would direct you to the joint consensus statement from the European College of Sport Science and the American College of Sports Medicine here. Clearly, optimising the balance between training and recovery and avoiding overtraining are priorities for professional athletes and those working with them – as Cook, Kilduff and Jones (2014) wrote: “Recovery is marked by the athlete’s return to resting function and physical performance… Clearly, recovering effectively is one of the most critical determinants of sport success.”
Accordingly, we view recovery as a tool that may help achieve success, potentially as a process that can gain a cutting edge and/or competitive advantage if well structured. In addition, we now have a greater understanding of the physiology of our sports and the time course of different aspects of recovery. For example, exercise-induced muscle damage may be present after a football match for at least 72 hours (Nédélec et al, 2012). Recently, post-match fatigue was examined further to dichotomise neuromuscular fatigue into peripheral and central drivers helping to highlight the complexity with the notion of “fatigue” (Thomas et al, 2017). Neuromuscular fatigue is recovered at 60 hours post- but not 36 hours post-match in a study in professional rugby union (West et al, 2014) and up to 48 hours post-match in rugby league (McLellan and Lovell, 2012). Perceptual wellness markers in Division I-A college (American) footballers are still reduced three and four days post-game compared to the day before the game (Fullagar et al, 2016).
We cannot wait until athletes reach baseline before training again but this information can assist with the planning and periodization of training and recovery in the days after competition, as well as allowing us to track individual responses. Whilst it is important to consider variations by sport, position, and individuals as well as the context and intensity of each game, research such as this gives us a starting point in understanding the physiological state of our athletes in the days after competition.
As well as understanding the subsequent effects of match-play on physical and perceptual markers on recovery, there is now a plethora of research available that investigate the effects of various recovery modalities. Whilst almost an endless amount of research is required to fully understand the effects of each modality to different sports and individuals, we have literature available on everything from compression garments, to water based recovery, and now cryotherapy. With this increased understanding of recovery, it is surely our duty as Sports Scientist to try to educate on, and strive to provide, the optimal recovery to each individual we work with as much as the setting allows – after all we have already established efficient recovery as a critical determinant of success in sport.
What does seem clear in recovery research is that sleep and nutrition are two essential pillars of good recovery. Sleep is a fascinating area that we still have so much to learn about and certainly the full effects of sleep on recovery and athletic performance are beyond the scope of this blog post. In recent times we have seen a growing focus on trying to assist sleep in the sporting world; from Swansea City’s snoozeboxes to AFC Bournemouth’s sleep packs. There is also a number of interesting case studies investigating the effects of sleep, travel and time changes, that have emerged over the past couple of years, such as:
- The Effect of Travel on Sleep and Recovery (Whoop Case Study) (Breslow, 2016)
- Effects of long-haul transmeridian travel on player preparedness: Case study of a national team at the 2014 FIFA World Cup (Fowler et al, 2017)
- Effects of northbound long-haul international air travel on sleep quantity and subjective jet lag and wellness in professional Australian soccer players (Fowler et al, 2015)
- Sleep, Travel, and Recovery Responses of National Footballers During and After Long-Haul International Air Travel (Fullagar et al, 2016)
- Evening electronic device use: The effects on alertness, sleep and next-day physical performance in athletes (Jones et al, 2017)
Whilst more work is needed, this work can provide a more scientific understanding of considerations surrounding travel. The discussion around sleep and travel also seems to be entwined in the debate of scheduling and resting, such as this great piece by Baxter Holmes about the NBA.
As the article discusses, Dr Cheri Mah (@CheriMah), NBA sleep consultant and research fellow at the UC San Francisco Human Performance Center, constructed the Mah Score based on eight fatigue factors, which in turn creates a “Schedule Alert” for those games that are most unwinnable based on the schedule. This system had 78% accuracy last season (2015/16) and 76% accuracy this regular season (2016/17) predicting so called “Red Alert” results, based purely on the scheduling and travel of certain back-to-back games. Of course we all know that performance is highly elaborate and extremely difficult to “predict” especially in a team setting, but it may well be that the schedule is at times having a substantial impact on the result.
The scheduling of sporting fixtures is a complex task and ensuring a completely level playing field throughout a season must be near-impossible. Therefore, understanding the impact of games and schedules on our athletes, as well as trying to establish best practice interventions to optimise recovery, are important responsibilities for the Sports Performance team. With this in mind, a number of research papers have investigated the effects of fixture congestion in professional football. Whilst more research is required, the current findings seem to suggest that physical and technical performance may not be affected but injury rates associated with matches during these times may be higher (Carling et al, 2011; Bengtsson et al, 2013; Dellal et al, 2013). There is a brief summary of research into congested periods here by Michael C. Rumpf.
Understanding Training Load
As well as an increasing understanding of recovery, we are also better placed to understand the load our athletes are subjected to, thanks to greater research and application of monitoring training load. Coupled with objective and subjective markers that permit the measurement of the individual response, we have the ability to build a powerful picture to understand each athlete’s programme. The focus with monitoring training load is to try to objectively prescribe the optimal balance between work and rest/stimulus and recovery. Whilst we have considered the importance of rest and recovery in this post, recent research suggests that chronic workloads, when achieved via a progressive increase, can assist in developing physical tolerance and resilience to injury (Bowen et al, 2016). Therefore, wrapping athletes in cotton wool and over-prescribing rest and recovery may in fact have detrimental affects on their physical capacity.
We have made great leaps in training load research in recent times but we must always remember the individuality of athletes as well as the complexity surrounding responses. First and foremost, the characteristics of an individual athlete, such as age, training age, and injury history, are the foundation for injury risk upon which internal and external factors are applied. Furthermore, we have so much to learn especially in emerging areas such as the gut microbiome, the brain’s influence in both the psychological and neurological aspect, the influence of genetics and epigenetics and a more thorough understanding of the biology of sleep. Monitoring training load and measuring fatigue responses have clearly become a key responsibility of Sports Science support and it may be based upon some of this information that decisions regarding rest and recovery are made. However, like with everything we must consider this is only one piece of a complex puzzle.
“Not in Our Day” vs “It’s Getting Tougher at the Top”
Much of these scheduling issues have always been the case, as ex-players are often quick to point out. For instance, there were previously many more back-to-backs as well as four games in five nights in the NBA. Manchester United played 63 games in their successful 1998-9 treble winning season. Plus, those playing in years gone by may have had it even tougher without chartered flights and swanky hotels to help them cope.
However, we also know that the physical and technical demands are increasing in many sports. Bradley and colleagues (2015) demonstrated various increases in physical and technical metrics in English Premier League matches between 2006 to 2013. The largest increase came in teams classified as Tier B - those finishing in 5th-8th place. This suggests an increase in competition in the top two tiers and a narrowing of the performance gap between them. Data across the same period of time also demonstrated an increase by 30% in high intensity distance and by 35% in sprint distance between the first and last seasson (Barnes et al, 2014). In another sport, a recent Sports Medicine review by McNamara et al (2016) demonstrated an increase in fast bowling workload over the past 20 years.
It would also seem that the mental demands surrounding sport have also increased, if we consider the impact of social media, technology and commercial demands for example. Neuroscientist Professor Vincent Walsh of UCL suggested elite sports performance has the highest mental demand of any activity, with the exception of military combat (2014). How often do we consider the mental rest required, as well as the physical rest? Do we only utilise recovery in response to physical load or do we also acknowledge the need to recover from the psychological demands of professional sport?
As always, it is important to ask “why” of any intervention we are putting in place and this goes for the topic of rest. We have only scratched the surface of complex topics such as recovery, sleep, training load, and the physiological demands of matchplay in this broad discussion on rest. Other areas such as nutrition, heart rate variability, measuring fatigue, psychology and early specialisation should also be considered. There are also more grand and somewhat philosophical questions such as “what is fatigue” and “what are we actually recovering from” that can make your head spin when contemplating this topic!
For now, I think I can summarise the preceding ramblings into the following points:
- We have a more quantified understanding of the physiological demands of matchplay and the time course of recovery across a variety of sports.
- We have a more in-depth understanding of the physiology of recovery and the effect of different modalities. Given that recovery has been identified as a critical determinant to sporting success, it is a substantial responsibility of performance support staff.
- We have more research available on monitoring training load and fatigue responses and, in many cases, now have access to more data pertaining to this area in the applied environment.
- The demands of our sports are increasing, both physically and mentally. Applying evidence-based science to our athletes to try to protect from injury and help optimize performance and potentially extend careers is a key responsibility.
Perhaps the biggest challenge in Physical Preparation/Strength and Conditioning/Sports Science has always been, and will always be, getting the balance right between stimulus and rest. Furthermore, this balance should always be considered on an individual athlete level. The media attention surrounding such a topic should not change our decisions but it does serve as a timely reminder to review and reflect on our philosophies and interventions and always ask why!
Barnes, C., Archer, D. T., Hogg, B., Bush, M., & Bradley, P. S. (2014). The evolution of physical and technical performance parameters in the English Premier League. International Journal of Sports Medicine, 35(13), 1095-1100.
Bengtsson, H., Ekstrand, J., & Hägglund, M. (2013). Muscle injury rates in professional football increase with fixture congestion: an 11-year follow-up of the UEFA Champions League injury study. British Journal of Sports Medicine, 47(12), 743-747.
Bowen, L., Gross, A. S., Gimpel, M., & Li, F. X. (2016). Accumulated workloads and the acute: chronic workload ratio relate to injury risk in elite youth football players. British Journal of Sports Medicine, bjsports-2015.
Bradley, P. S., Archer, D. T., Hogg, B., Schuth, G., Bush, M., Carling, C., & Barnes, C. (2016). Tier-specific evolution of match performance characteristics in the English Premier League: it’s getting tougher at the top. Journal of Sports Sciences, 34(10), 980-987.
Carling, C., Le Gall, F. and Dupont, G. (2011) Are physical performance and injury risk in a professional soccer team in match-play affected over a prolonged period of fixture congestion? International Journal of Sports Medicine, 33(1): 36-42.
Cook, C.J., Kilduff, L.P. and Jones, M.R. (2014) Recovering effectively in high performance sport. In: High-Performance Training for Sports. Human Kinetics, pp. 319-330. ISBN 978-1450444828
Dellal, A., Lago-Peñas, C., Rey, E., Chamari, K., & Orhant, E. (2013). The effects of a congested fixture period on physical performance, technical activity and injury rate during matches in a professional soccer team. British Journal of Sports Medicine, bjsports-2012.
Fullagar, H. H., Govus, A., Hanisch, J., & Murray, A. (2016). The Time Course of Perceptual Recovery Markers Following Match Play in Division IA Collegiate American Footballers. International Journal of Sports Physiology and Performance, 1-11.
McLellan, C. P., & Lovell, D. I. (2012). Neuromuscular responses to impact and collision during elite rugby league match play. The Journal of Strength & Conditioning Research, 26(5), 1431-1440.
McNamara, D. J., Gabbett, T. J., Naughton, G., & Orchard, J. W. (2016). How submarine and guided missile technology can help reduce injury and improve performance in cricket fast bowlers. British Journal of Sports Medicine, 50(16).
Meeusen, R., Duclos, M., Foster, C., Fry, A., Gleeson, M., Nieman, D., … & Urhausen, A. (2013). Prevention, diagnosis, and treatment of the overtraining syndrome: joint consensus statement of the European College of Sport Science and the American College of Sports Medicine. Medicine and Science in Sports and Exercise, 45(1), 186-205.
Nédélec, M., McCall, A., Carling, C., Legall, F., Berthoin, S., & Dupont, G. (2012). Recovery in soccer. Sports Medicine, 42(12), 997-1015.
Thomas, K., Dent, J., Howatson, G., & Goodall, S. (2017). Etiology and Recovery of Neuromuscular Fatigue following Simulated Soccer Match-Play. Medicine & Science in Sports & Exercise.
Walsh, V. (2014). Is sport the brain’s biggest challenge?. Current Biology, 24(18), R859-R860.
West, D. J., Finn, C. V., Cunningham, D. J., Shearer, D. A., Jones, M. R., Harrington, B. J., … & Kilduff, L. P. (2014). Neuromuscular function, hormonal, and mood responses to a professional rugby union match. The Journal of Strength & Conditioning Research, 28(1), 194-200.
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