Not All Sleep is "Good Enough" Sleep. What is Restorative Sleep and Why is it Important.
Updated: May 24, 2021
I recently heard an Army leader say "physical fitness will win a battle, but cognitive fitness will win a war." We spend our days challenging our brains and bodies at a very high operational tempo, but oftentimes, we forget about the most critical weapon system for benefiting both physical & cognitive performance: sleep. It is pretty clear that sleep is important. Technologies and products aimed to improve sleep is a billion dollar business. But what people often do not acknowledge is that not all sleep is the same. In order to perform at your best athletically and tactically, it is necessary and critical for sleep to be restorative.
What is restorative sleep?
Restorative sleep can be objectively and subjectively defined. Objectively, restorative sleep is sleep comprised of > 40% of the deepest stage (stage 3) of non-rapid eye movement sleep (NREM) and rapid eye movement (REM) sleep. During stage 3/NREM sleep, the body and brain shift from a catabolic to an anabolic state, replenishing energy stores at the level of the cell (e.g., ATP; Plante et al. 2014) and muscle (e.g., glycogen; Schmidt et al. 2014) to name a few. The body also releases anabolic hormones such as testosterone, growth hormone, and insulin growth factor, in order to further augment recovery (reviewed in Schmidt et al. 2014). The brain also clears waste/toxins from the brain (Eide et al. 2021). During REM sleep, the brain undergoes neuroplasticity. Neuronal connections and networks are re-defined and re-wired in order to help an individual retain and recall information the next day (Tononi et al. 2011). Subjectively, restorative sleep is defined by how "refreshed" or "rejuvenated" an individual feels upon awakening. Some people experience sleep inertia meaning that there is a lag between one's actual wake time and when one's brain actually performs and is vigilant/alert (Balkin et al. 1988). Sleep inertia can be conveniently masked or mitigated though by a cup of coffee (Newman et al. 2013).
Ways restorative sleep can be improved holistically rests on one's sleep environment. The three keys are:
o Dark room
o Cool room
o Noise-free room
What about limited opportunities for restorative sleep?
Achieving restorative sleep while traveling for competition, competing in competition, or during a military training exercise is limited and not easy. However, there are several fatigue management strategies developed by military science laboratories and academic partners that can be leveraged. A top three list and explanation of each are below. The bottom line up front (BLUF) is to plan ahead to get sleep prior to "go time" and set your sleeping environment up to be as sleep friendly as possible.
1. Sleep banking is a real thing.
There are several studies from the Army and in elite college athletes showing how extending sleep of normal, healthy young adults prior to anticipated sleep deprivation improve performance (Mah et al. 2017; Rupp et al. 2013) and emotional stability (Alger et al. 2019). Sleeping in > 60 minutes goes a long way.
2. Exercise tactical napping.
There are again several studies from elite college athletes showing that a < 30 min can help/preserve physical performance and cognition under high stress and fatigue/exhaustion resulting from training (Waterhouse et al. 2007; Soussi et al. 2020). For full effectiveness, it is best to align napping when fatigue and daytime sleepiness naturally set in in the middle of the afternoon. The circadian rhythm of daytime sleepiness is natural and an indication that the brain and body wants to rest.
3. Try to sleep at night as much as possible.
While sleep is like a bank account in that hours sleep during the day counts towards minimizing overall sleep debt, the most restorative sleep is pre-programmed for nighttime sleep (Tarokh et al. 2021). Humans have evolved to be day-active (diurnal) creatures for a reason. Even when sleep opportunities are limited, try to get as many hours at night before shifting to multiple naps across the day.
To conclude, how high performers think about sleep ought to be different than the general population. High performers must routinely perform under high stress and therefore, high performers have to leverage, exploit, and maximize the latest and greatest science of sleep and performance in order to leverage, exploit, and maximize recovery. Sleep technologies and products can help coax the process of restorative sleep but not to the extent that setting up one's environment and mindset can. An athlete's motto should and ought to be "sleep to perform!"
Major Allison J. Brager, PhD is an active duty Army neuroscientist leveraging sleep science discoveries to provide fatigue management solutions for military operations. She sits on fatigue management working groups for NATO, the United States government, and the Army Surgeon General. She has > 30 peer-reviewed publications in flagship sleep and neuroscience journals focused on identifying biomarkers that promote resiliency to sleep deprivation and expedite restorative sleep in extreme environments. MAJ Brager has co-authored chapters on sleep and performance for the NCAA and NASM in addition to serving as a sleep and performance consultant for professional, Olympic, and collegiate athletic programs. Her popular science book, "Meathead: Unraveling the Athletic Brain," bridges her own athletic anecdotes as a Crossfit Games and collegiate athlete with the latest neuroscience on elite athlete performance. At present, she is an astronaut applicant undergoing selection for upcoming missions via NASA. She trained under Dr. Mary A. Carskadon as an undergraduate at Brown University, received her PhD with Dr. David Glass at Kent State University, and did post-doctoral research with Dr. Ketema Paul at Morehouse School of Medicine and Dr. Tom Balkin at the Walter Reed Army Institute of Research.