BENEFITS

Sleep has such an enormous impact on athletics that scientists have called it "the most potent performance-enhancing activity that we know of."^30b Put differently, "there's nothing that you can do, there's no drug, there's no routine, there's no food you can eat that's going to have a bigger impact on your performance scientifically than the sleep you get at night."¹⁰¹ While age-group coaches remain largely unaware of this research, collegiate and professional teams are not. In fact, many teams have sleep consultants, including the Boston Bruins – who credit sleep scientist Dr. Peter Czeisler with helping them win the Stanley cup – the Portland Trail Blazers, Chicago Bulls, Boston Celtics, Miami Dolphins, New England Patriots, Philadelphia Eagles, Jacksonville Jaguars, Cleveland Browns, Chicago Cubs, Manchester United soccer, Chelsea soccer, Real Madrid Soccer, Team Sky Cycling, the entire United States Tennis Association, Tennis Australia, Stanford University, Oklahoma State University Football, Tennessee Volunteers Football, and the list goes on.^{30b, 30c, 30d, 30e, 43c, 30f,, 101} When defending national champion Clemson opened its new $55 million football complex in January, “its greatest benefit to player performance was its dedicated nap room.” ^30b So why is sleep now considered “the most cost-effective secret to sporting success”? ^30e As explained in detail below, sleep directly affects (1) reaction times, (2) skill and motor development, (3) muscle recovery and growth, (4) judgment, and (5) mental toughness.

(1) Reaction times

Sleep deprivation significantly impairs athletes' reaction times and ability to quickly spot visual signals.^{39a, 29, 66} This is in part because during sleep the body replenishes neurotransmitters, which are the chemicals that relay signals within the body.^39b As a result, athletes' reaction times speed up by at least 7 percent for every hour of improved sleep.¹⁰¹When elite collegiate swimmers increased their sleep as much as possible and Major League Baseball players slept 1.1 hours more per night for just five nights, their reaction times improved by 150 milliseconds (17%) and 122 milliseconds (13%, a fastball takes 400 milliseconds), respectively.^{31, 31a}. On the flipside, if adolescents get a moderate amount of sleep but not the 8-10 hours they need each night, the neurotransmitter "messengers" don't work as well and reaction time can diminish by over 18%.^30b And after just one night without sleep, or one week of sleeping four to five hours a night, reaction times triple.^{40a, 41b, 42b} This is an impairment in reaction times equivalent to being legally intoxicated.^{40a, 41b, 42b} As sports writers have pointed out, these slower reaction times result in more injuries, missed tackles, lost races, and "dunks that end up on SportsCenter" rather than "timely defensive rotations." ^{42a, 43b}

(2) Learning skills and motor development

Even elite athletes are constantly honing their motor movements and learning new strategies and skills, which is another reason why adolescents need to sleep at least 8-10 hours.^{37, 32} The first night following training is when the human brain learns whatever a person practiced during the day. ^{33, 40a, 32, 1, 2, 27} So contrary to the popular saying, it’s not practice that makes perfect but “practice, with sleep, that makes perfect”:^{33, 33a}

“Solidifying knowledge requires both REM and deep sleep. The first aspect, which happens during deep sleep, is basically a rehearsal: the brain files away the facts and practices the moves learned that day. The second part is integrating those facts and lessons into existing knowledge. This happens during REM.”^40a

Most REM sleep occurs in the “final quarter” of a full night of sleep³² – the time when we are currently waking up our teens to get ready for school. The result is that athletes “learn some new plays in practice, but it doesn’t become automatic, and come game time it might look as if they never practiced at all.” ^{32, 33, 40a} And catching up on sleep even on the very next night after practice doesn’t change this result, making “quality sleep on the first night after training critical.”^{32,33, 40a}

This is one of the many reasons that both the NCAA³² and the International Olympic Committee³⁶ have released guides for coaches and athletes explaining the adolescent sleep cycle shift and encouraging coaches and athletes to do whatever they can to adapt daily schedules to adolescents’ sleep cycle, rather than trying to adapt student athletes’ sleep cycles to current schedules. As the International Olympic Committee explained, there’s “a prevalence of insufficient sleep among adolescents, often prompted by early school-start times” and “interventions (tailored training and even perhaps schooling schedules) to support adequate sleep in youth athletes should be implemented.”³⁶

(3) Muscle recovery and growth

Sleep is also essential to muscle recovery and growth, tissue repair, and ordinary developmental growth in student athletes.^{41, 30b, 30e, 32, 32a, 33, 40a} Over 95% of (a) natural human growth hormone and (b) sexual maturation hormones are released during sleep.^{41, 30e, 32, 33}Human growth hormone is responsible for cell growth and regeneration – including muscle growth – and for regulating body composition.^{41, 30b, 32, 33} Testosterone, a sexual maturation hormone, has important beneficial effects on muscle mass, strength, vigor, and well-being in both male and female athletes.^{33, 40a}

When an athlete does not get enough sleep, the levels of both types of hormones drop dramatically.^{33, 40a} By way of example, after just one week of sleeping five hours or less each night, a man’s testosterone level falls as if he’s aged 11 years.^{43, 40a} And growth hormone drops so significantly with sleep loss that not only is there a negative effect on tissue healing and recovery, but research indicates that without enough sleep, a day’s training causes muscular atrophy, thereby making an athlete weaker rather than stronger.^{33, 44, 100}

(4) Judgement and mood

For beginning and professional athletes alike, getting more sleep reduces errors and improves judgment.^{32, 33, 40a, 40b, 30b, 43} For example, by sleeping more collegiate football players cut mental errors in half,^{30b, 101} while professional basketball players who slept less the night before a game committed significantly more technical fouls.^{40a, 44} Amongst younger athletes, sleeping 5 hours a night for only two nights has been shown to cause a 3x increase in lapses of attention⁴⁵ – even if the athletes are able to catch up on sleep on the weekends.⁴³

Why? Sleep loss causes a reduction in brain connections in the prefrontal cortex, which is responsible for judgment, and the amygdala, which is responsible for emotion.^40a Even minimal sleep loss lowers the threshold for containing anger because the amygdala can become 60 percent more reactive.^40b And, as the NCAA has explained, athletes need their prefrontal cortex functioning optimally because sports involve decision-making, and an athlete’s overall performance will suffer from errors caused by less sleep:

“Decision-making … is crucial on the field. In addition, as explained above, sleep loss also significantly decreases testosterone production which, for male and female athletes alike, impacts decision-making abilities in such a way that “there is no way a player is performing at his [or her] peak when testosterone is depleted.”^40aSleep loss impairs your ability to make creative thoughtful decisions. Worse, sleep loss even impairs individuals’ ability to be aware of their own impairments. This leads to overconfidence and a lack of insight into poor decisions.”³²

Sleep reduction also causes depression, poor moods, decreases in “vigor,” and, obviously, tired players.^{45, 46, 47} These are not the best mental states for any teen engaging in sports or even physical activity in general.

(5) Mental Toughness

Although some athletes seem to be naturally more resilient, mental toughness is a skill that that's improved through practice and sleep:

“The sneaky reality of mental toughness is buried in how well we recharge and recover. It's looking after ourselves physically and mentally so that we can "top up" our toughness for moments where we need it most.”^43e

Teenagers that sleep more have higher levels of mental toughness, in part, because sleep deprivation increases the perceived effort of a workout or competition, worsens mood as explained above, and causes an athlete's ability to stay focused to plummet.^{43e, 43g, 102}

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In sum and for the numerous reasons listed above, we now know that sleep may have “the most potential for positive impact on athletic performance”³⁰ – more than training modifications, coaching, nutrition, conditioning, etc. Even Michael Phelps, the most decorated Olympian in history, sleeps 11-12 hours a day and has said that training and sleep were equally important when it came to winning his 28 medals:⁶⁵

"I really can't say it enough. I don't think people really pay enough attention to how important sleep is.⁶⁵

And we also know that sleep deprivation causes athletes perform significantly worse and jeopardizes their safety, as illustrated in the info-graphic below. Simply put, sports scientists recommend that athletes and adolescent athletes in particular avoid early morning schedules -both in training and otherwise - to get more sleep.^{43d, 103} It is a unequivocal, scientific fact that student athletes cannot get the sleep they need each night to succeed to their full potential or stay safe unless middle and high school starts at 8:30 a.m. or later.^{66, 67} And it is an unequivocal, scientific fact that when schools have switched to later start times, students get more sleep.⁶⁷ In fact, students have had faster reaction times even when only one school day per week started an hour later.³⁶ The extra hour of sleep that these teenagers logged every week had a significant impact on their performance.³⁶ And many athletic directors at school districts that changed to later start times report that their teams performed better following the change and that general participation increased in their sports programs.^{37, 17} So as parents an coaches, it is time for us to read the science - like coaches and players in the NCAA and professional leagues - and stop using disruption of sports as an reason NOT to have later school start times. If we don't, much of our student athletes' efforts at practice will continue to go to waste.