After all that talk about intense workouts, lactate and the punishment we subject our knees to, there is one rather obvious question left.
How does the body actually recover from all of this?
We drink lots of water. We eat lots of protein. We give our joints and muscles a break.
But eventually, our bodies will demand the ultimate recovery tool: Sleep.
After a particularly brutal workout, I don’t know about you, but I’d happily take a good eight-hour system reboot and call it a day. Otherwise, my brain gets foggy and refuses to function at its peak, while just about every other part of my body starts reminding me exactly how hard I worked out the day before.
And that is precisely why sleep is so important.
We tend to think of sleep as simply the period when our bodies shut down and take a break from being awake. But that isn’t quite what is happening.
While we’re lying there unconscious and apparently doing absolutely nothing, our brains are engaged in a remarkably complicated process of regulating neural activity, hormones and immune signalling. There is a considerable amount of biological housekeeping going on behind the scenes.
And to understand why sleep is so important for recovery, we need to look at what is happening inside the brain when we transition from “wide awake and ready to go” to “please don’t disturb me until morning.”
One of the most important pieces of this puzzle is a rather familiar molecule from biochemistry: glutamate.
While we’re awake, our brains need to remain sufficiently active for us to think, move, learn and respond to our surroundings. One of the major neurotransmitters involved in this excitatory signalling is glutamate. As this article states,
Glutamate has excitatory effects on nerve cells, and that it can excite cells to their death in a process now referred to as “excitotoxicity”. This effect is due to glutamate receptors present on the surface of brain cells. Powerful uptake systems (glutamate transporters) prevent excessive activation of these receptors by continuously removing glutamate from the extracellular fluid in the brain. Further, the blood–brain barrier shields the brain from glutamate in the blood. The highest concentrations of glutamate are found in synaptic vesicles in nerve terminals from where it can be released by exocytosis. In fact, glutamate is the major excitatory neurotransmitter in the mammalian central nervous system.
Glutamate binds onto glutamate receptors on the surfaces of brain cells to excite them. In this way, our brain cells can operate better when we’re awake and in an “excited” state with the aid of glutamate.
However, we don’t want our brains to remain in a state of excessive excitatory activity when it is time to sleep. An overactive brain is hardly conducive to falling asleep, particularly when stress is keeping our thoughts racing.
Interestingly, our brains have the capability to regulate a healthy balance between wakefulness and restfulness by fiddling around with the levels of glutamate in our brains.
They do that by synthesizing glutamate decarboxylase (GAD) enzymes, which are capable of converting glutamate to γ-aminobutyric acid (GABA). A necessary cofactor, pyridoxal-5-phosphate (also known as Vitamin B6), supports the conversion of glutamate to GABA.
GABA is a neural inhibitor. Where glutamate excites the brain, GABA helps to calm down the brain. In simplified terms, we can think of this as part of the biochemical machinery that helps shift the brain from “stay alert and process everything” towards “calm down, we’re going to bed.”
But, as it is usually the case with biological systems, it isn’t quite as simple as having one neurotransmitter for being awake and another for being asleep. Our brains don’t have a little glutamate meter that gradually falls throughout the evening before a GABA meter takes over at bedtime.
Sleep is regulated by a much larger network of neurotransmitters, hormones and neural circuits, all interacting with one another to determine whether we remain awake or transition into sleep.
And this is where things get rather more interesting.
Our sleep-wake cycle is also governed by our circadian rhythm, an internal biological clock that helps coordinate physiological processes according to the time of day. Light is one of the most important signals used to keep this clock synchronised with our environment.
As evening approaches and our biological clock signals that it is time to wind down, the pineal gland begins producing more melatonin. Melatonin doesn’t exactly knock us unconscious like a sleeping pill. Rather, it acts as one of the signals telling our body that the biological night has arrived.
Which means that getting to sleep isn’t simply a matter of having enough GABA floating around in our brains.
Our brains need to know that it is actually nighttime too.
And there is yet another player in this rather complicated recovery programme: inflammation.
We have already seen how inflammatory signalling can influence the degradation and repair of our joints. Interestingly, the relationship also works in the other direction. Poor or disrupted sleep can influence inflammatory signalling in the body, creating yet another biological feedback loop.
Suddenly, our eight-hour system reboot doesn’t look quite so optional anymore.
Because insufficient or disrupted sleep cycles has been associated with increased oxidative stress and reactive oxygen species (ROS) production. And this is where our old friend oxidative stress makes another appearance:
Oxidative Stress Is An Electrochemical Concept That Focuses On An Inappropriate Rate Of Electron Transfer.
The electron is a particle that is responsible for transporting electric currents. Whenever we flick a light switch on at home, we’re connecting up a circuit that allows for the flow of electrons to power up a device that can then convert that electrical energy into light energy, such that our houses get illuminated.
Now, melatonin is an antioxidant in its own right, which means that it can be called on to neutralise the ROS.
When melatonin participates in this antioxidant defence, the molecule itself can be oxidised and converted into other metabolites. Once that happens, that particular melatonin molecule is no longer available to bind to melatonin receptors and contribute to the signalling of biological night.
And therein lies an interesting connection between sleep and oxidative stress: the very molecule that helps tell our bodies that it is nighttime can also help protect our cells from oxidative damage.
So far, we’ve spent most of our time looking at what happens inside the brain. But remember why we went to sleep in the first place.
We were trying to recover from that brutal workout.
While we sleep, the body doesn’t simply sit around waiting for morning. The physiological environment changes in ways that support recovery, including changes in hormone secretion, immune activity and tissue repair.
And this brings us back to something we discussed in the previous article: our joints and muscles are constantly being damaged, repaired and remodelled while we continue using them.
Sleep doesn’t magically repair every microscopic injury we accumulated during our workout. But it provides the body with the time and physiological conditions in which these maintenance processes can take place.
In other words, that eight-hour system reboot isn’t really a reboot at all.
It’s scheduled maintenance.
So maybe getting enough sleep isn’t being lazy after all.
It’s simply letting the maintenance crew do its job. After all, we can't expect the construction crew to finish the renovation if we keep turning the lights back on every few hours.
And if the maintenance crew needs raw materials to work with, that’s where nutrition comes into the picture.
Sleep may provide the maintenance window, but our cells still need amino acids, fatty acids, vitamins and minerals to actually carry out all that repair and housekeeping.
Which brings us neatly back to something we’ve discussed throughout this series: we can’t build a functioning body out of nothing.
So yes, get your eight hours of sleep. Eat properly. Stay hydrated. Exercise consistently.
Sleep provides the time for recovery, but the raw materials for recovery still have to come from somewhere. That means getting sufficient protein, essential fatty acids, vitamins, minerals and other nutrients from our diet.
If you're interested in the supplements I personally use to complement my diet, I've put my Usana recommendations here, because apparently even the maintenance crew has a shopping list:
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