The Underlying Importance of Sleep

by on December 6, 2012
in Injury Prevention

Originally published in Los Angeles Sport & Fitness, December 2012.

In college, I set my alarm for 5A.M. so that I could wake up, grab a banana, and drive to the Marina Del Rey boathouse to be on the water with the crew team by 5:30 A.M. Rowing early in the morning was practical, as the water was calm before the hubbub of the daily marina activities. Also, our meets were in the morning; we trained in a similar state to our performance state in terms of our Circadian rhythms.

The early-morning practices made sense practically, but they were not without consequences. One semester, I drove from the marina to campus for an 8:00 A.M. class. It was an easy class filled with athletes from various sports. The entire back of the lecture hall was filled with sleeping student-athletes who had morning practices or weight sessions.

Many sports teams practice before school; in sports such as swimming and rowing, early-morning practices are a fact of life. For other sports, like basketball, early-season practices take place prior to school due to the number of teams using the gym with overlapping volleyball and basketball seasons. Other coaches choose an early-morning practice time because of a belief that it develops toughness, discipline, commitment, or other important traits.

Every fall, as basketball season begins, writers celebrate coaches and players who wake early to practice. These players are described as tougher, and these coaches are praised for instilling discipline. Should we celebrate these coaches? Are early-morning practices good for adolescents?

Athletes and coaches are beholden to the old adage, “While you’re sleeping, someone else is getting better, and when you meet him or her in competition, he or she will beat you.” Is the adage true? Do the early risers have an advantage?

According to the American Academy of Sleep Medicine, teenagers require nine hours of sleep each night. Many adults believe that nine hours is excessive. My summertime sleep patterns as a teenager frustrated my parents who rose early for work. However, when one understands the important physiological, behavioral, and neurocognitive processes that occur during sleep, nine hours of sleep for a teenager makes sense. Sleep affects recovery, energy restoration, learning, memory, cognition, muscle growth and more.  Because children and teenagers are exposed constantly to new environments, skills, and information, they need time to consolidate these memories and skills, and this occurs while asleep.

A study published in Pediatrics found that adolescents lost as much as two hours of sleep during the week after school started (Hansen et al., 2005). Despite an earlier bed time, I would estimate that I lost at least two hours of nightly sleep when rowing. A 2008 study found that moving back the starting time for school by 40 minutes increased the students’ amount of sleep by 33 minutes (Htwe, 2008), suggesting that the students took advantage of the extra opportunity to sleep rather than staying up later at night. Students in early morning classes have reported being more tired, being less alert, and expending greater effort (Hansen et al., 2005), whereas the students who started their school day later reported less sleepiness during the school day (Htwe, 2008). An early-morning practice would have the same effect as moving up the start of the school day, meaning players who are less alert, more tired, and expending more energy.

Another study found that after sleep reduction, there was an 11% reduction in time to exhaustion and an increased perceived exertion (Martin, 1981). At a sports practice, a reduction in time to exhaustion and an increased perceived exertion will have a negative effect on practice performance. Athletes who tire more easily will engage in fewer quality repetitions, and increased perceived exertion will lead to less intensity. As an example, sub-maximal and maximal lifts were shown to decrease after four days of sleep restriction (Reilly & Piercy, 1994). Whereas the public believes that these athletes are working harder because they awake earlier, in reality, they may not work as hard as they would later in the day or after a full night’s sleep.

Sleep not only affects time to exhaustion or perceived exertion, but skill performance. In a study by Cheri Mah at Stanford University, players improved their sprint time, free-throw accuracy, and three-point accuracy after increasing their sleep time by 90 minutes (Mah et al., 2011). Sleep deprivation also can affect one’s ability to make split-second decisions, according to a 2009 study in Sleep. Whereas the study tested members of the military, successful athletic performance in most sports requires split-second decision-making.

Sleep also affects injuries in sports. In a study by Dr. Matthew Milewski presented at the 2012 American Academy of Pediatrics national conference, athletes who slept eight hours or more each night were 68 percent less likely to be injured than those who slept less. Sleep reduces mental and physical fatigue, and a less fatigued athlete likely is less prone to injuries.

Beyond sports and academic performance, sleep is important for health. A 2012 study published in Sleep found that insulin resistance can improve by 9% in teenagers if teenagers who slept six hours per night added one additional hour of sleep. Another study by Eve Van Cauter of the University of Chicago found that young adult males metabolized glucose less efficiently and had higher levels of cortisol when sleeping four hours per night compared to eight hours per night.

Whereas some people may concede that teenagers need more sleep, they will suggest that teenagers can go to bed earlier to compensate for the early-morning practices. This may not be within their control. Oxford professor Russell Foster suggested that the body clock of teenagers is programmed two hours later. The Washington Post reported that Mary Carskadon of Brown University found that melatonin, a sleep-promoting hormone, rose later in the night than in children or adults and remained higher in the morning. This may make it harder for teenagers to get to sleep earlier at night or to wake up earlier in the morning regardless of their intentions.

The National Sleep Foundation suggested that the strongest circadian dips — time period for sleep — occur between 3:00 and 7:00 A.M. A practice at 5 or 6:00 A.M. cuts into this peak period for sleep. Furthermore, Robert Sapolsky, author of Why Zebras Don’t Get Ulcers, described a study that found that participants’ stress hormones started to rise an hour before they woke up whether they woke up naturally (around 9:00 A.M.) or whether they were told when they would be awakened (6:00 A.M.). The implication was that an early alarm led to less quality sleep than one might expect as the body anticipated the alarm. For a teenager waking up for a 6:00 A.M. practice with a 5:15 A.M. alarm, his or her stress hormones would begin to secrete at 4:15 A.M., right in the middle of his or her peak sleep rhythms.

In basketball, early-morning practices have been celebrated at least since John Chaney started 6:00 A.M. practices at Temple University in the 1980s. There is a strong belief that these practices teach players something important. However, are these lessons worth the increased risk of injury, the skill decrements, and the potential health consequences from insulin resistance and elevated levels of cortisol? Parents often cannot determine practice times, and sometimes coaches have no control either, but in situations where there is control, are the benefits of early-morning practices worth it?

As a society, we tend to ignore the importance of sleep because we cannot see the important physiological, behavioral, and neurocognitive processes that occur when we are asleep. We can see a player run hard and appreciate the effort. However, we cannot see that his speed and effort are inhibited by a lack of sleep. If we understood these processes or could see the brain consolidating memories or the body secreting growth hormone to repair tissue damage, we would appreciate the role of sleep in academic, athletic, and daily performance more, and we might not be in such a rush to wake teenagers from bed.

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