Sleep, the overlooked recovery and performance tool

There is no exercise in rest, but there is the making of exercise in it (a nod to Victorian art critic John Ruskin).

The body recovers and restores during sleep, readying itself for the next day of activities. However, many athletes and active consumers shortchange their nightly slumber, foregoing the cognitive, emotional and physical benefits rest provides.

Adults need 7 to 10 hours of sleep per night, and younger athletes need even more, 8 to 10 hours, according to the American Sleep Association. Overall, the organization reported 35.3 million U.S. adults have a sleep disorder, with 37% of 20- to 39-year-olds and 40% of 40- to 59-year-olds admitting to short sleep duration.

Collegiate athletes have particularly challenging schedules that affect sleep habits and quality. In a 2015 survey by American College Health Association (ACHA), 29% of student athletes reported significant sleep difficulties, and 40% reported getting enough sleep on only ≤3 nights.¹ Among the sleep challenges, extreme difficulty falling asleep (for 3 nights or more) plagued 25% of student-athletes, while sleepiness was “a big problem” for more than 15% of respondents. Showing the compound issues these athletes face, more than 50% admitted sleep problems impacted academic performance.

A 2015 Pacific-12 Conference (PAC-12) report found student-athletes said sleep is the primary negative consequence of their sports time commitments, and 77% believed they got less sleep than non-athletes.²

The University of Arizona has been looking at sleep habits of student athletes and the effects of sleep on performance. Michael Grandner, assistant professor of psychiatry and psychology and director of the Sleep Health Research Center at the UA College of Medicine, and Amy Athey, director of clinical and sport psychology services for Arizona Athletics, were awarded an NCAA Innovations in Research and Practice Grant in 2016 and have added to their ongoing roster of sports sleep studies.

They developed Project REST, a sleep intervention model that uses education, tracking and technology to improve sleep for collegiate athletes. The initial study involved 40 student-athletes who undertook a two-hour education session on good sleep, followed by 10 weeks of tracking sleep habits using Fitbits, which detailed sleep duration and quality in conjunction with sleep diaries.

Results showed improved sleep quality and more energy, while insomnia and time lying awake in bed decreased. Specifically, roughly 83% of the student-athletes reported better sleep, nearly 89% believed their athletic performance was improved, and most reported less stress and more focus.

“With a really simple educational intervention and opportunities for learning over a number of weeks, student-athletes were able to make changes that had a real impact,” Athey said.

Grandner noted Project REST is a low-cost model that can be adapted nationwide for all students. "It's just education and support," he said. "There's no reason this should be limited to student-athletes."

The pair of researchers have continued their study of sleep in student athletes.

In 2019, they reported results of a study conducted with University of Arizona colleagues on the effects of insomnia and daytime sleepiness on concussion risk in 190 Division I athletes.³ Using a survey battery including the Insomnia Severity Index (ISI) and National Health and Nutrition Examination Survey (NHANES) Sleep module, they found an almost 15% higher risk of concussion among athletes with clinically moderate-to-severe insomnia and excessive daytime sleepiness two or more times per month.

Grandner was also involved in a 2019 study publication concluding insomnia, insufficient sleep and other sleep difficulties were associated with increased driving after drinking alcohol, more so in student-athletes than non-athlete-students.⁴

Of course, sleep problems continue to dog all athletes including elite and professional.

A 2017 study out of Finland looked at sleep quality, the prevalence of sleep disorders and the impact of a structured sleep counselling protocol in professional athletes.⁵ Of the 107 professional ice hockey players surveyed as part of the one-year observational study, one in every four players had a significant problem sleeping. All the athletes said sleep was essential for their health, and 75% of them believed counselling would improve their performance. In fact, counselling was found to significantly improve sleep quality.

Likewise, a 2017 study examined sleep quality, mood and ensuing athletic performance in 576 Brazilian elite athletes (404 men and 172 women) of individual and team sports.⁶ Researchers evaluated mood states (Brunel Mood Scale) and sleep quality (questionnaire) up to 60 minutes before the start of national and international sports competitions, and the relationship of sleep quality and mood states with performance (i.e., winning or losing) was evaluated using descriptive and inferential statistics (including logistic regression).

The results showed decreased odds of winning in athletes suffering poor sleep quality and low vigor and anger, whereas odds of winning were increased in athletes experiencing higher tension. “Thus, coaching staff and athletes should monitor athletes' sleep quality before competitions to ensure athletes are in the optimal condition for performance,” the researchers wrote.

Exploring the link between sleep and training load, Belgian researchers studied sleep patterns and training parameters in elite female artistic gymnasts, including youth (under 13), junior (age 14 to 15) and senior (World Championship) athletes.⁷ Using sleep logs, Rate of Perceived Exertion (sRPE) scale (training) and world rankings (performance), the researchers found total sleep time and sleep efficiency were highest in junior athletes; yet, these athletes had the highest training load, monotony and strain—under 13 and seniors had lowest training load.

Overall, total sleep time proportionally impacted the next day’s training load, while higher training load negatively impacted the following night’s sleep. Senior athletes had lower total sleep time the night before World Championship meets, compared to the average for the entire championship season, and a higher training load correlated to lower ranking.

Similarly, Australian researchers investigated the impact of training schedules on sleep in 70 nationally ranked athletes from seven different sports.⁸ Based on data collected from wrist activity monitors and self-reported sleep/training diaries over two weeks of normal training, researchers reported the athletes spent an average 8 hours and 18 minutes in bed, starting an hour before midnight. However, they only got an average 6.5 hours of sleep per night, waking up a little before 7 a.m., on average.

Sleep/wake behavior was different between training and rest days, with shorter time spent in bed, earlier sleep onset and offset, and less total sleep time on nights before training days, compared to rest days. The study also found sleep duration linked to fatigue, with less sleep leading to more pre-training fatigue.

The researchers suggested training schedule design should consider sleep and fatigue. “In cases where early morning starts are unavoidable, countermeasures for minimizing sleep loss—such as strategic napping during the day and correct sleep hygiene practices at night—should be considered,” they advised.

Sleep has a direct and measurable effect on performance, according to a 2019 study on endurance cycling athletes.⁹ In a crossover design, cyclists completed endurance time-trials on two consecutive days, once after normal sleep and once after sleep deprivation. Researchers found finishing time after twodays of sleep deprivation was 11% slower than after one day of sleep deprivation, and 10% slower than after two days of normal sleep. Intensity ratio, the rate of perceived exertion (RPE) to heart rate, was higher on the second day of deprivation than on the first day of deprivation and two days of normal sleep. The researchers concluded sleep helps to optimize endurance performance.

Sleep efficiency may impact the athlete’s metabolism, including the krebs cycle for energy production, according to a 2019 Japanese study on volleyball athletes.¹⁰ Those with better sleep quality (assessed with NemuriSCAN) had better sleep efficiency than those with lower sleep quality, despite similar total sleep time between the groups. Analyses of saliva samples also revealed differences in urea cycle and krebs cycle metabolites between the two sleep groups. Ultimately, better sleep quality was associated with faster difficult-task response time during heavy exercise.

Nutrition, sleep and performance

Sleep-wake cycles can be affected by nutrition, as well as lifestyle factors such as blue light exposure from device screen time.

One popular “energy” ingredient that has a potentially huge impact on sleep is caffeine—as high as 74% of elite athletes may use caffeine as an ergogenic aid prior to or during a competition.¹¹ Depending on dosage and timing, caffeine can negatively affect sleep latency, total sleep time, sleep efficiency and sleep quality.¹² This stimulant can also reduce high-rapid eye movement (REM) sleep while increasing wakefulness and arousal. The key factor may be intense exercise and caffeine consumption too close to bedtime.

Exercise physiology researchers from Catholic University San Antonio, Spain, reported supplementation with caffeine (6 mg/kg) did not improve the 800-meter running performance in male middle-distance runner, but did impair their sleep efficiency, awake times and awakenings, as measured by monitors.¹³ The results also showed caffeine reduced perceived sleep quality, including calm sleep, ease of falling asleep and feeling refreshed after sleep.

However, a major challenge for athletes is maintaining an optimal circadian rhythm, and caffeine can play a positive role. Traveling across time zones and engaging in early or late competitions can impact performance—on average, athletes’ peak performance is in late afternoon, with a low performance point around 3 a.m.¹⁴ Caffeine may improve daytime sleepiness after long travel by retraining hormonal rhythm and improving alertness and performance.

To adjust to odd schedules and travel, caffeine could be used in conjunction with melatonin, an endogenous hormone used to signal sleep. It lets the body know it’s time to sleep by regulating blood flow, blood pressure and sleep/wake-related hormones. The body’s melatonin levels rise in tune to darkness, which is one reason why too much screen light can be detrimental to sleep.

Grandner described supplemental melatonin as a potential clock-shifter, meaning it can reposition circadian rhythm to promote earlier sleep. Melatonin supplementation can help adjust to jetlag,¹⁵ but its effects on athletic performance are mixed. Performance can be reduced following melatonin ingestion; while cognitive effects can last as long as 5 hours, physical performance effects are usually more short-lived.¹⁶

One study investigated the effect of melatonin supplementation on short-term cognitive and physical performance in soccer players.¹⁷ The athletes underwent testing sessions eight, 12 and 16 hours after ingesting 5 mg of melatonin or placebo. Both cognitive and physical performance was better at 16 hours compared to eight hours for both melatonin and placebo. Medicine ball throw and handgrip strength performances were lower in the morning in the melatonin group compared to the placebo group. However, melatonin had no significantly different effect on performance at 12 and 16 hours compared to placebo. Therefore, the negative effects of melatonin were isolated to the morning (short-term), not the afternoon.

Like caffeine, creatine may be useful following sleep deprivation. In a small study of elite rugby players undergoing exercise trials following normal sleep (seven to nine hours) or sleep deprivation (three to five hours), acute supplementation with caffeine (1 or 5 mg/kg) or creatine (50 or 100 mg/kg) at 1.5 hours before exercise maintained skill level, even in sleep deprivation.¹⁸ Skill performance reduced significantly in the placebo group following deprivation.

The brain may be responsive to creatine supplementation, but the doses required for cognitive response may be larger than those typically taken for muscle benefits, according to a 2019 publication.¹⁹

“It appears that creatine is most likely to exert an influence in situations whereby cognitive processes are stressed, e.g., during sleep deprivation, experimental hypoxia or during the performance of more complex, and thus more cognitively demanding tasks,” the researchers wrote, adding evidence that creatine can reduce the severity of or improve recovery from brain injuries, such as concussions, is limited.

Gamma-aminobutyric acid (GABA) is an amino acid that serves as an inhibitory neurotransmitter in the brain. It relaxes neuronal excitability in the nervous system and can relieve anxiety and mental stress while promoting relaxation and sleep.^20,21,22,23 As a bonus, GABA affects pituitary gland function and controls growth hormone (GH) secretion, which can promote muscle growth and maintenance.²⁴

A 2019 publication revealed healthy men taking 100g of GABA (as PharmaGABA, from Pharma Foods International Co. Ltd) plus 10 g of whey protein daily for 12 weeks more effectively added muscle than did healthy men taking just 10 g of whey protein.²⁵ Resting growth hormone levels were significantly increased after four and eight weeks in the GABA group compared to elevation at just eight weeks in the whey-only group.

Monocot grasses (corn grass, wheat grass, bamboo grass) contain a metabolite (6-methoxybenzoxazolinone) that influences serotonin levels. A pair of sports nutrition researchers measured mood state (Profile of Mood States), sleep quality (Pittsburgh Sleep Quality Index), and sleep patterns (ZEO Sleep Monitor) before and after four weeks of supplementation with monocot grass extract in male and female athletes.²⁶ They found the supplement group had less tension, depression and irritability, compared to placebo; the extract group also fell asleep 33% faster, had 50% better sleep and 40% better sleep quality, and woke up 30% less than the placebo group.

Also from the plant world, ashwagandha (Withania somnifera) has been used in Ayurvedic medicine to induce sleep. Ashwagandha is considered an adaptogen, as it regulates or balances stress. The mechanisms of this plant’s constituents are not fully known, but its adaptogenic properties have shown promising psychological and physiological benefits, including strength adaptations and recovery leading to muscle increases.²⁷ In 2017, researchers reported a water extract of ashwagandha containing triethylene glycol as a major component induced significant amount of non-REM sleep with a slight change in REM sleep, while an alcohol extract high in active withanolides was ineffective at inducing sleep.²⁸ Additional research has indicated ashwagandha components may interact with GABA receptors to exert cognitive benefits such as improved sleep.²⁹

The research on nutritional interventions in sleep is still emerging but shows potential for micronutrients, amino acids and botanicals. (See page 21 for more info.) The research on supplementation, sleep and performance specifically in athletes is even more limited. However, when considering the mounting empirical and clinical evidence of the impact of sleep on athletic performance, brands have a ripe opportunity for formulation of sports nutrition products to include a primary or secondary focus on improved sleep.

References

1. American College Health Association. ACHA-NCHA II Spring 2015 Reference Group Data Report. Hanover, MD: ACHA; 2015 https://www.acha.org/documents/ncha/NCHA-II%20WEB_SPRING_2015_REFERENCE_GROUP_DATA_REPORT.pdf

2. Penn Schoen Berland. Student-Athlete Time Demands: Penn Schoen Berland; 2015. https://sports.cbsimg.net/images/Pac-12-Student-Athlete-Time-Demands-Obtained-by-CBS-Sports.pdf

3. Raikes AC et al. “Insomnia and daytime sleepiness: risk factors for sports-related concussion.” Sleep Med. 2019 Jun;58:66-74.

4. Bastien CH et al. “Driving After Drinking Alcohol Associated with Insufficient Sleep and Insomnia among Student Athletes and Non-Athletes.” Brain Sci. 2019 Feb 20;9(2).

5. Tuomilehto H et al. “Sleep of professional athletes: Underexploited potential to improve health and performance.” J Sports Sci. 2017 Apr;35(7):704-710.

6. Brandt R et al. “Perceived Sleep Quality, Mood States, and Their Relationship With Performance Among Brazilian Elite Athletes During a Competitive Period.” J Strength Cond Res. 2017 Apr;31(4):1033-1039.

7. Dumortier J et al. “Sleep, training load and performance in elite female gymnasts.” Eur J Sport Sci. 2018 Mar;18(2):151-161.

8. Sargent C et al. “The impact of training schedules on the sleep and fatigue of elite athletes.” Chronobiol Int. 2014 Dec;31(10):1160-8.

9. Roberts SSH et al. “Effects of total sleep deprivation on endurance cycling performance and heart rate indices used for monitoring athlete readiness.” J Sports Sci. 2019 Dec;37(23):2691-2701.

10. Akazawa N et al. “Effect of sleep efficiency on salivary metabolite profile and cognitive function during exercise in volleyball athletes.” Eur J Appl Physiol. 2019 Oct;119(10):2215-2223.

11. Del Coso j et al. “Prevalence of caffeine use in elite athletes following its removal from the World Anti-Doping Agency list of banned substances.” Appl Physiol Nutr Metab. 2011 Aug;36(4):555-61.

12. Clark I and Landolt HP. “Coffee, caffeine, and sleep: A systematic review of epidemiological studies and randomized controlled trials.” Sleep Med Rev. 2017 Feb;31:70-78.

13. Ramos-Campo DJ et al. “Impact of Caffeine Intake on 800-m Running Performance and Sleep Quality in Trained Runners.” Nutrients. 2019 Sep 1;11(9).

14. Baird MB and Asif IM. “Medications for Sleep Schedule Adjustments in Athletes.” Sports Health. 2018 Jan/Feb;10(1):35-39.

15. Herxheimer A et al. “Melatonin for the prevention and treatment of jet lag.” Cochrane Database Syst Rev. 2002;(2):CD001520.

16. Atkinson G et al. “The relevance of melatonin to sports medicine and science.” Sports Med. 2003;33(11):809-31.

17. Ghattassi K et al. “Morning melatonin ingestion and diurnal variation of short-term maximal performances in soccer players.” Physiol Int. 2016 Mar;103(1):94-104

18. Cook CJ et al. “Skill execution and sleep deprivation: effects of acute caffeine or creatine supplementation - a randomized placebo-controlled trial.” J Int Soc Sports Nutr. 2011 Feb 16;8:2.

19. Dolan E et al. “Beyond muscle: the effects of creatine supplementation on brain creatine, cognitive processing, and traumatic brain injury.” Eur J Sport Sci. 2019 Feb;19(1):1-14.

20. Abdou AM et al. “Relaxation and immunity enhancement effects of gamma-aminobutyric acid (GABA) administration in humans.” Biofactors. 2006;26(3):201-8.

21. Nakamura H et al. “Psychological stress-reducing effect of chocolate enriched with gamma-aminobutyric acid (GABA) in humans: assessment of stress using heart rate variability and salivary chromogranin A.” Int J Food Sci Nutr. 2009;60 Suppl 5:106-13.

22. Yoto A et al. “Oral intake of γ-aminobutyric acid affects mood and activities of central nervous system during stressed condition induced by mental tasks.” Amino Acids. 2012 Sep;43(3):1331-7.

23. Yamatsu A et al. “Effect of oral γ-aminobutyric acid (GABA) administration on sleep and its absorption in humans.” Food Sci Biotechnol. 2016 Apr 30;25(2):547-551.

24. Godfrey RJ et al. “The exercise-induced growth hormone response in athletes.” Sports Med. 2003;33(8):599-613.

25. Sakashita M et al. “Oral Supplementation Using Gamma-Aminobutyric Acid and Whey Protein Improves Whole Body Fat-Free Mass in Men After Resistance Training.” J Clin Med Res. 2019 Jun; 11(6): 428–434.

26. Talbott SM and Talbott JA. “Effect of Monocot Grass Extract (MGE) on mood state and sleep patterns in moderately stress subjects.” J Soc Sports Nutr. 2013 Dec; 10:P26.

27. Zeigenfuss TN et al. “Effects of an Aqueous Extract of Withania somnifera on Strength Training Adaptations and Recovery: The STAR Trial.” Nutrients. 2018 Nov; 10(11): 1807.

28. Kaushik MK et al. “Triethylene glycol, an active component of Ashwagandha (Withania somnifera) leaves, is responsible for sleep induction.” PLoS One. 2017 Feb 16;12(2):e0172508.

29. Candelario M et al. “Direct evidence for GABAergic activity of Withania somnifera on mammalian ionotropic GABAA and GABAρ receptors.” J Ethnopharmacol. 2015 Aug 2;171:264-72.