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Takeways for the effects of sleep restriction on gains
- Sleeping has many benefits. By cutting down on your sleep time, you’re missing out.
- You lose considerably more muscle and less fat when dieting in a sleep-restricted state.
- You have a considerably higher injury risk when in a sleep-restricted state.
- Your ability to perform decreases when you’re sleep deprived. Your ability to perform maximal volumes goes down along with your ability to produce maximal force.
- Lack of sleep increases hunger (primarily when hypocaloric), risk of psychiatric disorder, perception of exertion/pain while also decreasing emotional regulation, cognitive performance and motivation.
- If you’re ever sleep deprived, you might want to train in the morning rather than in the afternoon, despite training in the afternoon being potentially superior. Additionally, consider taking caffeine, as this may help recover performance, alertness, motivation and perceived effort to former, well-rested levels.
- Sleep more. Recommendations for optimal sleep durations will be included in next week’s post.
Sleeping is important.
While that statement may seem obvious to you, you might not quite realise how important sleep is, and how dramatically inadequate sleep can lower your quality of life. On the other hand, if, like myself, you’ve ever suffered from a sleep disorder for an extended period of time, you know exactly what I am talking about.
In no particular order, sleep restriction:
- decreases performance across a wide array of cognitive tasks, such as focusing
- decreases emotional regulation and motivation and increases risk of psychiatric disorders
- increases hunger (via increased ghrelin and decreased leptin, for instance)
- increases pain perception and risk of developing further chronic pain disorders
More pertinent, however, is the question of how sleep restriction affects your results in the gym.
What about your ability to perform?: “Inadequate Sleep and Muscle Strength: Implications for Resistance Training” Knowles et al. (2018)
- Sleep restriction impacts your ability to perform both across sets and maximal force production. Hence, you probably want to have an “easy” session after a rough night.
- Sleep restriction seems to impede more strongly and quickly on compound movements than on isolation exercises, and perhaps more strongly and quickly on lower body compounds than upper body compounds.
- Sleep restriction increases perception of exertion and catabolic hormone circulation, while also decreasing anabolic hormone circulation.
- Caffeine intake can have a considerable positive impact if sleep deprived, perhaps even recovering performance entirely depending on magnitude of sleep restriction
- You may perform better in the morning after sleep restriction rather than in the afternoon
This review looked at 17 studies. The protocols in the individual studies varied, and all studies were rated as being of weak-moderate EPHPP quality assessment tool scores.
One interesting tendency across the studies was that a) upper body movements “required” more sleep restriction to be negatively affected than lower body movements and b) compound exercises “required” less sleep deprivation to be impacted than isolation exercises.
Additionally, several studies reported that cortisol was elevated and testosterone was decreased after sleep restriction of various lengths. This’ll be discussed in the “Mechanistic rationales for sleep being detrimental to gains” section.
Also worth noticing is the fact that sleep restriction negatively impacts both maximal force production and your ability to maximise volume across sets. This review also suggested that performance may be better in the morning after a night of sleep restriction than in the afternoon. Hence, it might be worth to train in the morning rather than in the evening if you ever have a night’s poor sleep, or even consistently poor sleep – though, in that case, you’d be much better served getting your physician to help solve the disorder itself as your first-line recourse.
What about injury risk? “Chronic Lack of Sleep is Associated With Increased Sports Injuries in Adolescent Athletes” Milewski et al. (2014)
- There was a strong negative linear relationship between sleep duration and injury risk. As sleep duration increased (up to 9 hours), injury risk decreased. Below are correlation coefficient calculations; one includes all 5 data points (as shown above) while the other only included 4. The reason for exclusion is that I suspect there simply weren’t sufficient subjects sleeping 5 hours a night for it to be a very reliable data point. Regardless, the relationship for the 5 data points is considered strong (1<|r|>0.8), while the coefficient for the 4 data points was near perfect (|r|->1).
- Finally, here’s the data I used for analysis; since the exact amounts weren’t given in the full-text paper, I resorted to approximating data from their graphs. Hence, the graph/calculations may contain minor mistakes; however, the trend holds true.
Honestly, I think the findings are pretty self-explanatory in this one. If you sleep more, you’ll have a much lower acute injury risk. I suspect this is partly due to cognitive impairment when you’re sleep deprived, and partly due to a lower recovery ability amongst the sleep-deprived subjects. The findings of this study probably aren’t 100% transferable to resistance training, since most other sports are much more dynamic, cognitively demanding and injurious, but I’d bet the trend still applies to lifting as well.
What about weight/fat loss? “Insufficient sleep undermines dietary efforts to reduce adiposity” Nedeltcheva et al. (2010)
- Caloric intake was tightly controlled. No resistance exercise was performed. Macronutrient intake was not reported. Sleep was assessed via EEG.
- Over a time span of two weeks, sleeping 5.25 hours resulted in the same weight loss as sleeping for 7.25 hours. However..
- When sleeping 5.25 hours, the group lost 55% less fat than when sleeping 7.5 hours. Additionally, they also lost 60% more LBM (Lean Body Mass) than when sleeping 7.5 hours.
- When sleeping 5.25 hours, Resting Metabolic Rate (how many calories you burn when at rest) decreased when compared to sleeping 7.5 hours a night – more so than it should have based only on the differences in weight from weight loss.
- Sleeping more makes you lose less muscle and more fat (proportionally) than if you slept less. However, you probably won’t lose much more weight if you just sleep more. That’s almost entirely dependent on caloric balance – whether you are in a hypercaloric (consume more calories than you burn), eucaloric (consume as many calories as you burn) or hypocaloric state (consume fewer calories than you burn).
This study investigated weight loss and its relationship with sleep restriction. The findings suggest that, by sleeping less, you’re promoting fat retention and muscle loss. Moreover, the study also found that ghrelin (hormone stimulating hunger) concentrations increased, whereas leptin (hormone inhibiting hunger) concentrations did not decrease. Notably, concentrations of various catabolic hormones such as cortisol were not found to be increased.
Here’s the dataset from Nedeltcheva et al.:
A few aspects are particularly noteworthy. First off, as previously mentioned, there was more LBM loss and less fat loss in the TIB 5.5 condition than in the TIB 8.5 condition. Secondly, RMR decreased in TIB 5.5 compared to TIB 8.5. This suggests that sleeping for less time might have a negative impact on RMR, meaning you’d have to either eat less or move more to lose the same amount of weight than if you slept more. As such, sleeping more could be said to directly aid weight loss by promoting a higher RMR level.
Mechanistic rationales for sleep being detrimental to gains
Now that we’ve looked at how inadequate sleep affects performance and weight loss, let’s try to explain why it could potentially affect strength and muscle gain negatively.
Lack of sleep increases the levels of various catabolic hormones such as cortisol while simultaneously decreasing levels of various anabolic hormones such as testosterone. The evidence isn’t crystal clear on this, but it would make sense mechanistically. Some studies do show a reduction in anabolic hormone concentrations and increase in catabolic hormone concentrations, while others find no difference. At the very least, lack of sleep certainly doesn’t help with those two aspects of muscle growth.
What are anabolic and catabolic hormones? Briefly put, catabolic hormones are hormones that lead to the breakdown of molecules into smaller units. In the case of muscle, catabolic hormones promote the breakdown of Muscle Protein (the stuff that makes up your muscle) into Amino Acids. On the other hand, anabolic hormones promote the build-up of molecules from smaller units. In the case of muscle, again, anabolic hormones promote the synthesis of new Muscle Protein using Amino Acids.
So, inadequate sleep increases the blood levels of hormones decreasing your results while also decreasing the blood levels of the hormones increasing your results.
Moreover, we’ve established that lack of sleep increases injury risk. Injuries can negatively impact your ability to perform certain movements with the same confidence and vigor as you previously did. Hence, a reduction in volume might be observed, which, as we know, is perhaps the biggest factor for muscle growth.
Additionally, the increased perception of pain from lack of sleep may also play a role in perceived exertion – how hard you feel you’re working. When sleep-deprived, you’ll probably feel like you’re working harder than you really are and feel tired a lot more easily. Anecdotally, I have found this to hold true, and have found caffeine intake to help remediate it.
A final mechanistic reason that is primarily pertinent to weight loss over muscle gain is ghrelin increases and leptin decreases in response to inadequate sleep. Some studies suggest it does happen, while others find no significant difference in ghrelin/leptin concentrations between normal sleep and sleep deprivation conditions. These changes seem to primarily appear when the subjects are both hypocaloric and sleep deprived. Anecdotally, I have noticed that people on diets do tend to be more hungry when sleep deprived.
We have evidence and mechanistic reasons to believe sleep enhances performance and results. If you want better results, sleep more. It’s probably the “easiest” way of improving your quality of life and achieving better results – it’s free and doesn’t take much effort.
Part 2 of this series, recommendations for sleep, is on its way next week. It’ll be a bit shorter than this article, but will contain more practical information on how long you should sleep and why.