Sleep. Very few of us get enough of it, because of stressors with work, family, or in my case, school. Indeed, two years ago I went back to school to get a Doctor of Physical Therapy (DPT) degree. Since that time I’ve unwillingly been a test subject in my own perverse sleep deprivation study.
But I’m going to follow Beyonce’s lead and make some “lemonade” by sharing some facts with you about sleep. We’ll start with the most logical question…
Why do you need sleep?
For eons, scientists have known that sleep is restorative and essential for memory formation. That’s why we need it. But until recently, they weren’t really sure how sleep is restorative. In 2013, a landmark study in the revered Science journal helped explain what’s going on.
While you’re awake, little pieces of protein called beta-amyloid clump together and form plaques. These beta-amyloid plaques are found in the small spaces between the brain’s nerve cells. But if these plaques hang around those small spaces for too long, they can wreak havoc by blocking signals and triggering inflammation in the brain.
In fact, an accumulation of beta-amyloid plaques is closely linked with Alzheimer’s Disease. Yep, that’s how bad those suckers are.
Now, back to the study. The researchers found that sleep opens up small areas of the brain that allows cerebral spinal fluid (CSF) to rush in and clear out the beta-amyloid plaques that accumulated during the day (Xie et al, Science, 2013). Think of CSF as being your brain’s housekeeper.
Sleep’s other function – the formation of memories – is also really important. But I’m not just talking here about learning how to remember calculus formulas or a list of random facts for History class, I’m also talking about memories related to movement. Motor learning, in other words.
When you’re training to improve your technique in, say, an Olympic lift, the brain must increase the strength of its synapses related to that exercise in order to learn how to do it better. How does the brain increase its synaptic strength? While you sleep, it rehearses that Olympic lift.
Let’s say you practiced the snatch lift yesterday afternoon. When you were sleeping last night, your brain activated the same neurons necessary for that movement to occur. It was literally rehearsing what you did so those synapses could get stronger – that’s how motor learning occurs.
However, this mental movement retraining only happens during the rapid eye movement (REM) sleep cycle. There are four stages of sleep that range from drowsiness (stage I) to deep sleep (stage IV). It takes about an hour to get through all four stages. REM is a separate aspect of sleep and it occurs 4-5 times during a normal night of sleep. Each phase of REM sleep gets progressively longer, from 10 minutes early in the night to 50 minutes before waking up.
During REM, your brain releases the neurotransmitter, glycine, which blocks the normal connection you have between your brain and muscles while awake. This glycine release, in essence, makes your body paralyzed, which allows your brain to rehearse the snatch lift without any actual movement taking place. This is akin to a pilot learning how to fly on a flight simulator.
Pretty cool, eh?
How much sleep do you need?
According to research, most people get around 7.5 hours of sleep each night. That falls within the 7-9 hour range recommended for adults (18-64 years) by the National Sleep Foundation.
But if you get 7.5 hours of sleep every night, I can say two things. First, I’m jealous. Second, you’re not like the vast majority of people I know. Indeed, I believe that sleep deprivation is a more widespread problem than some research indicates.
If you sleep any less than 7 hours your risk of weight gain, heart disease and diminished brain function significantly increases. Surprisingly, these same risks are associated with getting more than the recommended 9 hours each night. However, I’m willing to bet that the people who consistently get 10 or more hours of sleep per night are unhealthy because of other reasons related to laziness and poor nutrition.
For me, one night of 10 continuous hours of sleep makes my brain sharper and my body stronger. So I’ll take it whenever I can – maybe after I graduate?
If you can’t get 7 hours of sleep at night, make a point to squeeze in a nap during the day. It’s best to get 60-90 min if possible (Mednick et al, Nat Neurosci, 2003), but a nap as short as 6 minutes has been shown to be beneficial and can improve brain function (Lahl et al, J Sleep Res, 2008). There’s no better recovery aid than a nap after you train.