By Jeremy R. Hawkins, PhD, LAT, ATC; Michael Reeder, DO; and Alli Powell, DAT, LAT, ATC
Sleep – that magical state where our bodies recuperate, our minds rejuvenate, and we are free of the everyday stresses of the world – is a necessary physiological process that all humans require. This article, the second in a series, will explore the role of sleep in performance, an area that is just now gaining traction in both sports and the business world.
Sports and exercise scientists have studied many aspects of how to improve performance, including physical training, nutrition, and supplements, as well as changes in equipment, with a significant amount of time, resources and money directed at these approaches, all with the goal to improve our capabilities. An area of more recent study in exercise science, and financial investment in both the athletic and corporate world, is sleep and its impact on performance. From the University of Oregon to the Boston Red Sox to Manchester United to Google, athletic teams and businesses are very interested in optimizing sleep for their athletes and employees in order to gain the competitive edge on the court, the field, or in business. These investments and interventions include the use of sleep pods, personalized mattresses, daily sleep-related smartphone questionnaires, and the hiring of “sleep coaches,” all in order to optimize the quality and benefits of sleep. While most of us do not have access to many of these resources, the benefits of sleep related to performance still apply to all.
Sleep is essential to many biological functions related to memory, cognition, and learning, as well as numerous physiological processes. This has been recognized since ancient times but has become a prominent topic of discussion more recently, perhaps related to the technological advances in measurement of sleep. Although the exact mechanism of sleep related to these physical and mental functions is not clearly understood, most experts agree on the overall importance. As we had noted in our first article (“Sleep Series Part I: Basics of Sleep and Its Role with Injury,” January 2021, page 37), the general reason we sleep is to allow recovery from wakefulness and prepare for the demands of the next day, making it a restorative and reparative process.1 Unfortunately, when we sleep poorly for several nights, the impact spreads across very different areas of our lives, including changes in appetite regulation, immune function, cognitive impairment, and neuromotor performance, as well as fluctuations in mood/mental health.2,3,4 These mental and physiological process changes impact the physical and mental performance of our daily lives.
Sleep debt, also called a sleep deficit, is the difference between the amount of sleep someone needs and the amount they actually get. For example, if your body needs 8 hours of sleep per night, but you only get 6—you have 2 hours of sleep debt. – National Sleep Foundation
Sleep and Mental Performance
Regarding our mental performance, effective cognitive functioning is essential in all walks of life and adequate sleep has been shown to be imperative for optimal mental function. The loss of even a few hours of sleep has been shown to have detrimental impact on language processing, attention, working memory, inhibitory control, and decision making.5 These areas have a direct effect on our executive function and memory consolidation, both of which have significant impact on our occupations and personal relationships.
These specific effects on mental function likely contribute to the findings from studies of general workers in the United States that have demonstrated evidence for loss of employee productivity and worsening performance and safety outcomes secondary to loss of sleep.6 In the medical field, the hours worked by providers was first evaluated in physicians in the 1980’s. These initial studies indicated that resident physician fatigue negatively impacted their cognitive functioning and performance resulting in increased medical errors. In addition to having a relationship to patient health, more recently it is recognized that fatigue and lack of sleep likely impacts the health and well-being of physicians and other medical providers themselves.7 Many of these initial studies in both industry and medicine looked at the impact of the “night shift” or shift work, and the research demonstrated that this disruption in sleep had a negative impact on normal circadian rhythms and caused sleep debt with multiple physiological changes, elevated risk of poor health, and increased risk to overall safety.8 Within medicine, these studies led to the accrediting bodies restricting work hours for resident physicians in 2003. In some industries, these findings also have led to the promotion of sleep education, flexible work schedules, and even nap pods.
Sports Performance and Sleep
In the athletic world, performance has long been recognized as multifaceted and many studies have focused on the importance of training, conditioning, and nutrition related to improving performance in the athlete. More recent studies that have looked at the importance of sleep and the athlete’s performance have illustrated that both increase and decrease in quantity of sleep has an effect on performance.9,1 It has been recognized that in addition to the basic benefits of sleep in athletes, sleep is an important component of recovery.10 Clearly, overall athletic performance is impacted by neuromotor control, cognition, motor memory, balance, and focus, and sleep can have an impact in all of these areas. In general, when looking at the benefit of sleep related to different areas of performance, most studies have shown less effect related to single bouts of exercise or maximal performance with decreased quantity of sleep. More prominently, the most common consequences linked to performance are associated with deficits in the essential skills of many athletic contests and pursuits.9,10
Loss of Sleep is Detrimental to Performance
When looking at the impact of impaired sleep in athletes, studies indicate that maximal measures of strength appear to have minimal change with sleep loss but sustained efforts, sports specific skills, reaction time, fine motor movements and physical recovery, appear to show the most impairment.9,10
The effect of sleep loss or deprivation has been studied in many very different sports, such as strength athletes, judo, competitive darts, swimmers, volleyball, and shooting sports. These studies have shown an interesting and varied impact on performance, such as decrease in lap times in swimmers, decline in accuracy in competitive dart throwers, changes in strike zone judgement in baseball, and a decrease in overall power in the judo athlete.11
In an interesting study which combines performance, sleep loss, and the social aspect of the athlete, Jones and colleagues looked at the tweeting behavior of 90 NBA players and showed that late night tweeting was associated with a decrease in points scored and shooting percentage.12
Sleep Extension Improves Performance
In contrast, while there are methodological challenges when evaluating sleep in general and the impact of sleep extension, the majority of the research related to sleep extension has demonstrated the benefits for the athlete. For example, Mah et al had Division I basketball players purposefully increase their sleep quantity to 10 hours in bed per night. The athletes reported improved subjective feelings of physical and mental well-being and had improved sprint times and shooting percentage.13 Another similar study evaluated the effect of increase in sleep time with a collegiate tennis team and found that the increase in sleep quantity was related to an improvement in service accuracy.14 In studies involving baseball players, a small increase in average sleep time over 5 days improved visual attention and cognition, essential skills for success as a hitter in baseball.15 In a professional rugby pre-season training camp, Swinbourne et al showed that a sleep extension program resulted in improved total sleep time and quality as well as improved reaction time. In addition, they also found beneficial changes in stress hormone expression in the rugby athletes, which would be important to performance, recovery, and overall wellness.16
In addition, sleep extension has been considered in professions where there are unique sleep circumstances and work demands, such as military, law enforcement, and fire fighters, who are sometimes called “tactical athletes.” As an example, in a study looking at young ROTC participants, participants undergoing a sleep extension intervention demonstrated improved executive functioning, motivation, and psychomotor vigilance. 17
What Is Sleep Quality?
Generally, good sleep quality is defined by the following characteristics: (1) You fall asleep soon after getting into bed, within 30 minutes or less. (2) You typically sleep straight through the night, waking up no more than once per night. (3) You’re able to sleep the recommended amount of hours for your age group. (4) You fall back asleep within 20 minutes if you do wake up. (5) You feel rested, restored, and energized upon waking up in the morning. – National Sleep Foundation
Recovery or Extra Benefits?
One of the very interesting parts of this research brought up by Kutscher and Silva, is that it is unclear whether the benefits of extra sleep are from recovery of a baseline sleep deficit or does extra sleep provide physiological benefits to improve performance. These authors point out the many challenges of evaluating sleep, concerns regarding how it is analyzed, and the normal variation that is found with sleep in individuals, all of which make sleep extension or “sleep banking” evaluations challenging.18,1
While there is reasonably clear evidence that adequate sleep is important for optimal functioning in many walks of life, there is still much to learn about how much sleep is needed and what is the best way to evaluate sleep both during research studies and for the average person with a watch/fitness tracker that attempts to quantify their sleep. Although the application of the technique of sleep extension or banking sleep may be an important intervention in many walks of life, there is still much to learn in this area of sleep science. It is likely more important to first work on simply obtaining adequate sleep as an initial step to improve performance, no matter your occupation.
It is important to spread awareness of the importance of sleep to our family, friends, employees, and athletes to improve many physiological and psychological factors in their lives. In addition, in many avenues of life, adequate sleep may lead to improved performance, productivity, and an improved general well-being. 7
So perhaps the daily nap remains very important!
Stay Tuned. The third installment in this series will cover practical suggestions to improve sleep for our patients and ourselves, including the athlete looking to optimize their performance by maximizing the benefits of sleep.
Jeremy R. Hawkins, PhD, LAT, ATC, is an associate professor and the Department Head for the Department of Kinesiology, Colorado Mesa University, Grand Junction, Colorado. He also serves as the Program Director for the Master of Science in Athletic Training program. Hawkins routinely conducts therapeutic modality research, focusing on whether common treatment approaches help or hinder the healing process.
Michael Reeder, DO, board-certified in emergency medicine, is Director of the Monfort Family Human Performance Lab, Colorado Mesa University, Grand Junction, Colorado. He is Director of Medical Education for Cycling CME, a provider of continuing medical education for physicians, Physician Assistants, and other healthcare providers. Reeder holds a Certificate of Added Qualifications Fellowship in Primary Care Sports Medicine.
Alli Powell, DAT, LAT, ATC, is an assistant professor in the Department of Kinesiology, Colorado Mesa University, Grand Junction, Colorado. She also serves as the Coordinator of Clinical Education for the Master of Science in Athletic Training program. Powell’s scholarly interests focus on quality patient care through a variety of novel treatment paradigms.
- Silva AC, Silva A, Edwards BJ, et al. Sleep extension in athletes: what we know so far – a systematic review. Sleep Med. 2021;77:128-135.
- Belenky G, Wesensten NJ, Bamundi A, et al. Patterns of performance degradation and restoration during sleep restriction and subsequent recovery: a sleep dose-response study. J Sleep Res. 2003;12(1):1-12.
- Speigel K, Leproult R, Van Cauter E. Impact of sleep debt on metabolic and endocrine function. Lancet. 1999;354(9188):1435-9.
- Grandner MA. Healthy sleep for student-athletes: a guide for athletics departments and coaches. http://www.ncaa.org/ health-and-safety/sport-science-institute/ healthy-sleep-student-athletes-guide- athletics-departments-and-coaches.
- Diekelmann S. Sleep for cognitive enhancement. Front Syst Neurosci. 2014;8:46.
- Rosekind MR, Gregory KB, Mallis, MM, Brandt SL, Seal B, Lerner D. The cost of poor sleep: workplace productivity loss and associated costs. J Occup Environ Med. 2010;52(1):91-98.
- Gates M, Wingert A, Featherstone R, Samuels C, Simon C, Dyson MP. Impact of fatigue and insufficient sleep on physician and patient outcomes: a systematic review. BMJ Open. 2018;8(9):e021967.
- Patterson PD, Ghen JD, Antoon SF, et al. Does evidence support “banking/extending sleep” by shift workers to mitigate fatigue, and/or to improve health, safety, or performance? A systematic review. Sleep Health. 2019;5(4):359-369.
- Bonnar D, Bartel K, Kakoschke N, Lang C. Sleep interventions designed to improve athletic performance and recovery: a systematic review of current approaches. Sports Med. 2018;48(3):683-703.
- Halson SL, Juliff LE. Sleep, sport, and the brain. Prog Brain Res. 2017;234:13-31.
- Fullagar HH, Skorski S, Duffield R, Hammes D, Coutts AJ, Meyer T. Sleep and athletic performance: the effects of sleep loss on exercise performance, and physiological and cognitive responses to exercise. Sports Med. 2015;45(2):161-86.
- Jones JJ, Kirschen GW, Kancharla S, Hale L. Association between late-night tweeting and next-day game performance among professional basketball players. Sleep Health. 2019 Feb;5(1):68-71.
- Mah CD, Mah KE, Kezirian EJ, Dement WC. The effects of sleep extension on the athletic performance of collegiate basketball players. Sleep. 2011;34(7):943-950.
- Schwartz J, Simon RD. Sleep extension improves serving accuracy: a study with college varsity tennis players. Physiol Behav. 2015;15:541-544.
- American Academy of Sleep Medicine. “Sleep extension improves response time, reduces fatigue in professional baseball players: Short-term sleep loading can improve sports performance.” ScienceDaily. ScienceDaily, 5 June 2017. sciencedaily.com/releases/2017/06/170605085329.htm.
- Swinbourne R, Miller J, Smart D, Dulson DK, Gill N. The effects of sleep extension on sleep, performance, immunity and physical stress in rugby players. Sports (Basel). 2018;6(2):42.
- Ritland BM, Simonelli G, Gentili RJ, et al. Effects of sleep extension on cognitive/motor performance and motivation in military tactical athletes. Sleep Med. 2019;58:48-55.
- Kutscher S. Sleep and elite athletic performance. Practical Neurology. March 2019. Available at https://practicalneurology.com/articles/2019-mar-apr/sleep–elite-athletic-performance. Accessed June 10, 2021.