Ah, sleep. We all know how much we need it, mostly because when we don’t get enough, the world takes on a different, more negative hue. Lights seem brighter and sounds more vivid, and not in a good way. Perpetual fogginess clouds our thoughts, slurs our words, and prevents us from focusing on anything but the coffee pot timer. And then there’s the sleep deprivation research corroborating our experiences and explaining in lurid detail just how vital sleep is for our health. I’ve done my part in bringing this information to you, focusing for the most part on the metabolic health benefits of getting sufficient quality time with everyone’s sweet slumbery mistress. I’ve linked to articles discussing the links between poor sleep and ill liver health, disrupted metabolic function, and cancer. If you’re a regular reader of MDA, you’re probably aware of all this. Bad sleep can make you fat, sick, and prone to serious degenerative diseases.
That’s not the focus of today’s post, though. Today is for the people who miss out on sleep to catch an early morning workout, who stay up late reading fitness blogs and trading fitness memes on Reddit, who tell themselves that all that yawning they do in between squat sets is just weakness leaving the body. Did you know that sleep deprivation also hampers our athletic performance? That bad sleep makes us slower, weaker, and less coordinated? That sleep deprivation reduces the effectiveness of our workouts, and sometimes even reverses their beneficial effects? That it can hamper our ability to build lean mass?
Let’s look at some of the research.
Sleep and Muscle Mass
Lean mass accrual is a common motivation among fitness enthusiasts. Muscle looks good, makes us stronger, tends to accompany other benefits like increased bone density and fat loss, and helps keep us alive longer. There are a few lines of evidence suggesting that sleep loss increases the loss of lean mass and makes it harder to build it in response to exercise.
- One older study found that total sleep deprivation increases urinary excretion of nitrogen, which could be indicative of muscle breakdown and loss of lean mass.
- Sleep-deprived rats experienced muscular atrophy, an effect that appeared to be mediated by decreases in testosterone and increases in corticosterone (the “rat cortisol”).
- A more recent one found that insufficient sleep curtailed the efforts of obese human subjects to lose body weight and retain lean mass. Compared to the control group, the bad sleep group saw their lean body mass losses increase by 60% and their fat mass losses decrease by 55%. Markers of fat oxidation were reduced as well, suggesting that lean mass was being broken down into amino acids for energy.
Simply put, lack of sleep is a potent stressor, which means it increases the catabolic glucocorticoid family of hormones like cortisol and decreases the anabolic triad of testosterone, IGF-1, and growth hormone, effectively accentuating the “degradation pathways” while reducing the “protein synthesis pathways.” Few of us are experiencing the total sleep deprivation of 24-36 hours used in some of these studies, but 5-6 hour nights – chronic low-level sleep deprivation, the kind that’s endemic nowadays – do add up and exert many of the same effects, as shown in the study on obese humans limited to 5.5 hours a night.
Sleep and Performance
The effect of sleep deprivation on physical performance can’t be neatly summed up with a few tidy sentences. Sometimes it impairs performance and sometimes it has no effect at all. It really depends on what you’re measuring and what the subjects are actually doing. For endurance work, acute sleep deprivation doesn’t impair performance as much as you’d think, whereas for activities that demand greater motor control (like basketball or volleyball) or greater power output, acute sleep deprivation may have more negative effects. Let’s look at some of the studies that have been conducted.
- One night of sleep deprivation reduced the amount of air taken into and expelled from the lungs during exercise in endurance runners and volleyball players. It also decreased the time until exhaustion, more so in the volleyball players.
- 30 hours of sleep loss hampered maximal output, but not endurance.
- Anaerobic performance was impaired by 36 hours of wakefulness, while 24 hours had no effect.
- Partial sleep loss (2.5 hours total sleep) had no effect on maximal muscle strength in women.
- Severe (120 hour) sleep deprivation reduced the aerobic oxidation capacity in skeletal muscles and accentuated their reliance on the glycolytic pathway, effectively turning otherwise healthy skeletal muscles into pre-diabetic muscles.
- 24 hours of wakefulness did not have an adverse effect on the performance of collegiate weightlifters.
- Sleep loss reduces tolerance of prolonged exercise, via psychological rather than physical avenues. End result is the same, I’d argue.
- Sleep loss reduced sprint performance by lowering muscle glycogen content.
Of course, that’s just talking about acute sleep deprivation, like going a night or two without sleep. That type of sleep deprivation is easy and inexpensive to study, because you only need the subjects for a day or two, but I’d argue that it isn’t very relevant to most people’s concerns. What I’m interested in are the effects of chronic sleep deprivation, like getting six hours of sleep every night for a year. Many, perhaps most, people are getting suboptimal sleep on a nightly basis. That’s tougher to study, because you need to track subjects for days, weeks, or (ideally) months and years (an expensive undertaking), but I think you can make some educated guesses:
Consider that during slow wave sleep, growth hormone is released to build muscle and repair tissue damage. If you’re not sleeping, or your sleep is disrupted, you’re going to limit slow wave sleep (which already begins to decrease in duration the older you get) and therefore limit your body’s ability to recover from and adapt to your training.
Consider the protein-wasting, lean mass-catabolizing characteristics of sleep deprivation described earlier. A big part of adapting to training and improving performance is the increase in lean mass that usually accompanies exercise. If you’re not sleeping, you’re limiting your ability to pack on lean mass and increase performance.
Consider the increased cortisol and decreased testosterone associated with bad sleep. A high cortisol:testosterone ratio is strongly linked to “declines in the maximal voluntary neuromuscular performance capacity.”
And finally, consider that getting more sleep than normal, or accruing sleep surplus, has repeatedly been shown to increase physical performance:
- In a study, aiming for at least ten hours of bedtime each night over several weeks improved the Stanford men’s basketball team’s free throw and three point field goal percentages.
- In swimmers, six to seven weeks of ten hours of sleep a night decreased their 15-meter sprint time by half a second, increased their speed off the blocks, improved their turn time, and increased their kick stroke by five kicks.
- In college football players, six to seven weeks of ten hours of sleep a night decreased their shuttle run and 40-yard dash times.
What does this mean, in practical terms?
To get the most out of your workouts, and to be the best you can be, you need more sleep. Aim for ten hours, an unrealistic goal for most, but a worthy one nonetheless.
If you can avoid it, work out at a reasonable time that allows you enough sleep. Skipping sleep to exercise may be counterproductive, or at least less effective than working out at a time that allows sleep. If you absolutely need your daily morning WOD, go to bed early enough to make up for it.
Take naps when and where you can. Sleep adds up, no matter where it comes from.
As training intensity or volume increase, so too must sleep. There isn’t an easy formula or anything. Just sleep more.
That’s all well and good, but not everyone can get perfect sleep all the time. In the event of an unavoidable night of bad sleep, what can you do to ameliorate the negative effects on performance the next day?
- Meditate. Meditation is an effective counterbalance to the negative cognitive effects of poor sleep, some of which include hampered reaction times.
- Drink coffee. As always, caffeine is a dependable stalwart. It increases the “voluntarily chosen resistance training load” after a night of poor sleep, for one.
- Take creatine. Creatine has also been shown to reduce the negative effects of a poor night’s sleep on performance about as well as caffeine.
We all know how much sleep matters, but we rarely think about its effect on our strength and fitness. Hopefully this post helps you realize the extent of its reach. If you want optimal results, you cannot compromise on sleep, nor can you train your way out of a deficit.
Thanks for reading, folks!