By Matt McNamara
The line between simply being good and great is very narrow. Indeed it is often noted that the difference between the top tier of riders in the European peloton is between 1% and 3% in any given race, and that’s erring on the extreme side of generosity. As we’re seeing right now at the 2010 Olympics, podium placings and four years of training can be separated by hundredths of a second. The search for an advantage is ongoing and contributes to the continual evolution of technology and training. Think of the changes in aerodynamics and component design over the last ten years. Previously I’ve written about some of the cutting edge strategies employed in hydration and nutrition in the search for additional performance. Today we look a little deeper at the role of sleep in performance. First let’s look at sleep in general.
The Sleep Cycle
Sleep is defined as “a natural periodic state of rest for the mind and body,” characterized by a general decrease in activity and the onset of a rhythmic brain-wave cycle. The cycles of brain-wave activity are broken into four (or five) different stages as measured by an electroencephalogram (EEG). A normal cycle lasts about 90 minutes.
Stage one lasts five to ten minutes and is considered a transitional state. Theta waves, slow brain waves of 4-7 cycles per second (CPS), predominate. A typical night’s sleep is about 5% stage one.
Stage two is longer at approximately twenty minutes per cycle, and represents 45 – 55 percent of a regular night’s sleep. During this stage Theta waves continue to deepen and there is a decrease in heart rate, breathing rate, and body temperature. This stage also sees the onset of intermittent “sleep spindles,” short bursts of high activity that are primary markers of entry into Non-REM sleep (NREM). More on that in a minute.
Stage three sees the start of delta wave activity in the 3 cycles per second range. This stage is often considered a transitional stage towards true deep sleep and is measured in combination with stage four.
Stage four, or deep sleep, is often 30 minutes or more and delta waves make up more than 50% of brain activity. In concert with stage three they represent roughly 15-25% of a night’s sleep. Dreams can occur here, but this is not the start of REM sleep.
After stage four the mind transitions itself back to stage one and the onset of REM sleep. REM or Rapid Eye Movement, sleep is the state where dreams occur. Heart rate often rises and brain activity is close to levels seen when awake. Initially REM lasts about ten minutes, but lasts longer with each successive stage, and can reach nearly an hour. REM sleep represents approximately 25% of a nights rest. The graph below illustrates the stages of sleep very well:
In a normal nights rest one can expect to cycle through the different stages three to five times. This is where, for the performance athlete, the rubber meets the road.
Classical Sleep Research
Researchers have looked at the role of sleep on performance for many years. During that time the studies have looked primarily at the effects of sleep deprivation on performance.
In a classic 1984 Study Bruce Martin at Indiana University looked at the “Effect of Sleep Deprivation on Tolerance of Prolonged Exercise.” He sought to investigate the physiological, psychological, and performance effects of acute sleep deprivation.
Participants in the study were asked to perform extended treadmill walking at 80% of VO2max after a normal night’s sleep, and after being deprived of sleep for 36 hours before the treadmill test. In the sleep deprived trial total endurance was decreased by 11% on average. Interestingly, perceived exertion was significantly higher, while heart rate and metabolic rate were unchanged between the two trials, suggesting that psychological factors played an important role.
Also of note was the trending of participants to be either resistant or susceptible to the effects of sleep deprivation. Half of the participants showed performance decreases of less than 5%, while the other half trended more susceptible to sleep deprivation with performance declines of between 15 – 40%.
In a 1998 study Meney, Waterhouse, et al looked at the effects of one night of sleep deprivation on mood, physical performance and temperature for a group of individuals of varying regular activity levels.
This study had participants perform a series of tests every four hours over two days, with sleep deprivation being induced in the second round of trials. Participants were measured on core temperature, muscle strength (grip strength and back/leg strength), and self selected work rate on a cycle ergometer. They also completed a “Profile of Mood States” self evaluations at each phase to track variables like tension, depression, anger, vigor, and fatigue across trials.
The results showed no significant impact on physical performance as measured by perceived exertion, heart rate, or self selected work rate after a single bout of sleep deprivation. Of interest was a tendency to have a significant decrease in muscle strength that tracked with a similar decrease in core temperature and self reported vigor at a single point in the trial (specifically the 6th round of testing). The authors speculated that these factors may indicate the role of circadian rhythms (the natural changes in numerous physiological factors over the course of a day) or a de-activation of the central nervous system.
So it seems that acute sleep deprivation, for example in the night before a competition, is not an impediment to the physiological systems of performance, but may contribute to psychological impairment.
Current Sleep Research
The sleep deprivation studies serve as an important baseline, but they miss a couple of critical components I think. Specifically the role of chronic sleep deprivation on performance and the restorative role of sleep physiologically.
In a 2005 presentation Dr. William Dement from the Stanford Sleep Disorders Clinic and Research Center, discussed the role of Sleep Extension and getting as much sleep as possible.
He looked at the role of “chronic partial sleep loss” and the cumulative effect it has on day to day alertness. Dement summarized research around the idea of sleep latency, or how quickly one tends to fall asleep during the daytime (sleepiness). When subjects have their nightly sleep reduced by exactly the same amount over time they tend to exhibit more proclivity to fall asleep during the day. For athletes this general trend may not seem very important, but let’s look at the next component, sleep debt.
Sleep Debt is the term used to define the total amount of lost sleep over time. That is to say that it appears that every hour of lost sleep has an impact, and that the impact is inclusive of hours lost last night as well as hours lost weeks ago. Fortunately, this debt can be repaid by simply sleeping more. Dement noted that several landmark studies have shown that extending one’s sleep allows the debt to be paid back and that there is an optimal amount of sleep extension needed to do so.
In his summary of research Dement pointed to one of his studies showing improvement in sleep debt after just four days of sleep extension. Another study showed that when allowed to maximize sleep, participants would tend to sleep between 10 -12 hours in the first seven days, gradually dropping to an equilibrium point of about 8.5-9 hours per night after 21 days. This means that essentially you need to sleep a lot to pay back the debt, but that once repaid you can maintain equilibrium by optimizing sleep. Note that these studies were not conducted on athletes in a training environment.
Sleep and Performance
As laboratory performance is impacted by acute sleep deprivation, it can be assumed that athletic performance is as well. Dement included a quick summary of the role of sleep on performance. Unfortunately, there is little substantive research on the role of sleep extension on performance. Anecdotal evidence points to improvements in performance measures in self reporting.
Despite the paucity of rigorous study on sleep’s role in performance, there are areas where the benefits are substantive. Specifically in recovery and regeneration of essential proteins like Human Growth Hormone (HGH). It has been shown that HGH is an important building block responsible for increasing calcium retention, muscle mass (sarcomere hyperplasia), and promoting gluconeogenesis (glucose from non-carbohydrate sources).
HGH production peaks approximately an hour after the onset of sleep, but importantly it has been suggested by Mehta et al that over 50% of HGH production occurs during the third an fourth REM cycles. Given an average sleep cycle of 90 minutes, that means you need at least six hours of continuous sleep to start to maximize HGH production
Most athletes agree that sleep is an essential component of performance. The specific role of sleep on performance falls into two categories: acute sleep deprivation and chronic sleep debt. It has been shown in numerous studies that the physiological parameters of performance are not negatively impacted by short bouts of sleep deprivation prior to exercise, but that nearly all of us are sleep deprived and carry some amount of sleep debt everyday. Fortunately, by dramatically increasing your sleep over a period of time you are able to pay down this debt. This sleep extension has proven anecdotally beneficial to athletes and is an area for much greater research in the future. One area where additional sleep is particularly beneficial is in the production of Human Growth Hormone. HGH production peaks about 60 minutes after the onset of sleep, but more than 50% of HGH production occurs after the third REM cycle.
Boree, George C. – Sleep via Online Sleep Article (including image used above). Psychology Department, Shippensberg University 2003
Dement, William C. Sleep Extension: Getting as Much Extra Sleep as Possible, Clinics in Sports Medicine. 2005. 251-268
Martin, Bruce. Effects of Sleep Deprivation on Tolerance of Prolonged Exercise, European Journal of Applied Physiology. 1981 47: 345-354
Mehta, Ameeta and Hindmarsh, Peter. 2002. The use of somatropin (recombinant growth hormone) in children of short stature. Pediatric Drugs. 4: 37-47.
Meney, Isabelle, Waterhouse, Jim, et al: The Effects of One Nights Sleep Deprivation on Temperature, Mood, and Physical Performance in Subjects with Different Amounts of Habitual Physical Activity. Chronobiology International 1998 15 (4), 349 – 363.
About Matt McNamara: Matt is a USA Cycling Level 1 coach with over 20 years of racing, coaching and team management experience. This spring he is continuing his Performance Webinar Series that explores a variety of ways to improve your racing and training. He is the founder and president of Sterling Sports Group. Learn more by visiting his website at www.sterlingwins.com.