Sleep is one of the most effective and underused recovery modalities in the United States.  Before the advent of electricity, humans averaged 10 hours of sleep a night.  According to the latest gallop pole, Americans average 6.8 hours of sleep a night (down an hour from 1942).  It is still not fully understood why we sleep although there are many theories as to why.  One theory is that sleep allows for procedural learning, brain stimulation, and localized recuperation processes; while another theory is that sleep allows for the growth and development of the brain and nervous system (Siegel, 2005).  Sleep is not only necessary from brain functioning however, it is mandatory for weight loss, improved health, and muscle gain as well.

Sleep is divided into different stages.  There is stage W (or wakefullness), stage R (REM or rapid eye movement), and non-rapid eye movement sleep (NREM) which has three subdivisions (NREM 1,2, and 3).  Human adults enter NREM first and rapidly descend through the stages of NREM sleep within 15-20 minutes and cycle through the various stages of NREM and REM three to four times prior to waking with REM increasing in length each time.  It has been theorized that REM sleep is vital for encouraging brain and nervous system growth and NREM is vital for replenishing sugar in the brain and brain functioning (Caia, Kelly, and Halson).

The circadian rhythms are composed of different physiological and behavioral processes such as the sleep-wake cycle, body temperature, and hormonal regulations.  Various things wreck havoc on our circadian rhythms like the light-dark cycle, disruptions to our environment (traveling and staying somewhere new or in a different time zone), and stress.  All of these can cause our sleep-wake cycle to become desynchronized which can affect emotional regulation, core temperature, and circulating levels of melatonin (a hormone that is released when the sun goes down to relax our bodies and prepare them for sleep) and all of this delays the onset of sleep.  If this occurs for long periods of time, this leads to sleep deprivation.

Sleep deprivation is an insufficient amount of sleep and it leads to poor performance, reduced motivation and arousal levels, and reduced cognitive processes leading to poor attention and concentration (Marshall and Turner).  Obviously, whether your goal is to learn a new skill (learn how to squat, learn how to power clean, learn the newest Zumba moves, or improve agility) sufficient sleep is going to be your best friend.  Sleep deprivation also effects us physiologically as well as mentally.

Lack of sleep is a major factor in injuries.  A study by Milewski et al. looked at athletes and their average amount of sleep per night over 21 months.  For the athletes who slept 5 hours per night on average, there was a 60% chance of injury.  The athletes who slept 6 hours per night on average had a 75% chance of injury.  The athlete’s who slept 7 hours per night on average had a 65% chance of injury.  8 hours of sleep dropped the risk of injury from 65% to 35% and 9 hours of sleep dropped the risk of injury to 18%.  This shows that the more sleep a person gets, the less likely they are to get injured, so the goal should be to get 8-9 hours of sleep per night.

If fat loss is your goal, the more sleep you get the better.  Sleep deprivation has been associated with increased body fat levels.  Partial sleep deprivation leads to increased caloric intake with no effect of caloric expenditure, which leads to a net positive energy balance, which leads to increased fat gain (Khatib, Harding, Darzi, and Pot).  Studies show that sleep deprivation enhances pleasure seeking processing in the brain underlying the desire to consume food (Chaput and Tremblay).  Sleep deprivation also changes the way glucose (sugar) is metabolized and ALL carbohydrates are broken down into sugar.

To build muscle tissue, an increase in muscular strength needs to happen.  Knowles, Drinkwater, Urwin, Lamon, and Aisbett found that inadequate sleep decreased muscular strength on compound movements (ex. squats, bench press, and deadlifts).  It has been found that resistance training can prevent muscle loss due to sleep deprivation but, there are no improvements in muscle mass and strength.  It goes without saying, if your goal is to bet bigger or stronger, this is far from optimal.

Now that you know how important sleep is and the downfalls of inadequate sleep, the question becomes what can you do to improve sleep?  There are many steps that you can take to increase the likelihood of a good nights sleep.  The first step is to turn off all electronics 60-90 minutes before bed time.  Electronics like phones, tablets, and computers emit a blue light that suppresses melatonin levels delaying the onset of sleep.  Develop a pre-bed routine that you do everywhere, this will tell your mind and body that it is time for sleep.  Go to bed and wake up at the same times everyday as doing so will develop routine to make it easier to fall asleep and wake up.  Stress is a major source of sleep disturbances.  Find ways to de-stress before bed like meditation, writing in a journal, talking about what is bothering you, or taking a hot bath.  Make your room as dark as possible as light disrupts sleep (even from an alarm clock) and as cool as possible (65 degrees is the best room temperature to sleep in).  The last step is to avoid caffeine at least three hours before bed (preferably five hours before bed).  If you have a bad nights sleep, napping for no more then 30 minutes can make up the sleep debt and consuming a cup of coffee before hand can eliminate the grogginess after a nap.

References:

Fullagar, Hugh, H.K., Skorski, Sabrina, Duffield, Rob, Hammes, Daniel, Couttes, Aaron, J., Meyer, Tim.  Sleep and Athletic Performance: The Effects of Sleep Loss on Exercise Performance, and Physiological, and Cognitive Responses to Exercise  Journal of Sports Medicine 45 (2): pp. 161-182 2015

Khatib, HK, Al., Harding SV, Darzi, J., Pot, GK. The Effects of Partial Sleep Deprivation on Energy Balance: A Systematic Review and Meta-Analysis. European Journal of Clinical Nutrition (2016) 1-11 https://doi.org/10.1038/ejcn2016.201

Chaput, Jean-Philippe, Tremblay, Angelo. Insufficient Sleep as a Contributor to Weight Gain: An Update. (2012) 1:245.  https://doi.org/10.1007/s13679-012-0026-7

Marshall, Geoff, Turner, Anthony, N. The Importance of Sleep for Athletic Performance. Strength and Conditioning Journal: February 2016 38(1) pp. 61-67 https://doi.org10.1519/SSC.000000000000189

Knowles, Olivia, E., Drinkwater, Eric, J., Urwin, Charles, S., Lamon, Severine, Aisbett, Brad. Inadequate Sleep and Muscle Strength: Implications for Resistance Training. Journal of Science and Medicine in Sport 21(2018) 959-968 https://doi.org/10.1016/jsams.2018.01.012

Gao, Burke, Dwivedi, Shashank, Milewski, Matthew, D., Cruz, Aristides, I. Chronic Lack of Sleep is Associated With Increased Sports Injury in Adolescents: A Systematic Review and Meta-Analysis. Orthopedic Journal of Sports Medicine 2019.  7(3) https://doi.org/10.1177/2325967119S00132