High-Intensity Training Protects Muscles from the Effects of Sleep Loss

Sleep is important for good health…and so is exercise. A new study investigated how these two lifestyle factors might interact.

Studies (many in rodents) have shown that sleep deprivation (some have gone up to 72 hours) increases processes in the muscle that are responsible for protein breakdown (termed catabolic) and muscle atrophy (loss of muscle mass).

This seems intuitive, since sleep is also known to be a time of repair and regeneration for our muscles. It’s very likely that muscle protein synthesis (MPS) increases during sleep. Interestingly, many studies have shown that ingesting protein before bedtime can enhance MPS during sleep…but that’s a tangent for another day.

LOSING sleep, therefore, could be a recipe for reductions in muscle mass over an extended period of time. A transient fall in MPS might not be all that detrimental…but stack up enough nights of poor quality sleep, and your bulk might suffer.

This has implications for athletes and really, anyone looking to build muscle or prevent muscle breakdown. Especially relevant to this topic is the fact that around 48% of Americans don’t get a proper amount of sleep.

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The new study, titled “The effect of sleep restriction, with or without high intensity interval exercise, on myofibrillar protein synthesis in healthy young men”, sought to determine how moderate sleep restriction influences protein synthesis. Not only that…but it investigated a potential “counter attack” against sleep-restriction induced declines in protein synthesis. Their antidote of choice was high-intensity interval exercise (HIIE).

Like most exercise (including weight training), HIIE, even aerobic (cardio)-based, can increase muscle protein synthesis. Little is known, however, about what happens when you exercise in the context of not getting enough sleep.

The hypothesis was that, while sleep restriction would reduce MPS, performing exercise DURING a period of sleep restriction would prevent this decline. Basically, exercise would keep muscle protein synthesis levels equal to those during normal (adequate sleep)…or perhaps bring them to levels above baseline?

Let’s take a look at the study design.

24 young men were split into three groups. One group was assigned to get 8 hours of sleep per night for 5 nights (normal sleep or NS group).

Another group (the sleep restriction or SR group) would get only 4 hours of sleep for 5 nights.

The final group (SR + exercise) would only get 4 hours of sleep per night, but would perform 3 sessions of high-intensity exercise on day 2,3, and 4 of sleep restriction.

The HIIE session was pretty short (but intense). It consisted of alternating 10x30 second-intervals at 90% of participants’ maximal power output (Watts) on a stationary bike, interspersed by a 75 second rest period. They performed this HIIE session at 10 a.m. each day.

The research team took muscle samples (a muscle biopsy) at the beginning and end of the study. They also collected saliva samples from participants. These biological samples would be used to measure study outcomes including fractional synthetic rate (FSR) — a measure of myofibrillar protein synthesis (MyoPS) — and take a look at genetic pathways involved in protein synthesis and degradation signaling.

Results

As expected, MyoPS was lower in the sleep-restricted group compared to the normal sleep group.

However, there were no differences between the normal sleep group and the sleep restricted group who performed exercise. Essentially, exercise prevented the decline in muscle protein synthesis due to sleep restriction.

While MPS was altered, the study found no significant changes in molecular pathways responsible for protein degradation or synthesis. Similarly, the content of proteins involved in MPS (including AKT, mTOR, and p70s6k) were unchanged.

This study shows that just 5 nights of sleep restriction — to about HALF of a “normal” bed time — reduces protein synthesis in healthy young men. In fact, MyoPS was about 19% lower in the SR group compared to normal sleep or normal sleep + exercise groups.

This brings up the interesting question of whether or not “vulnerable” populations (older adults or those with diseases) might suffer even more from these negative effects of sleep restriction. Older/diseased populations are known to have more sleep problems and reduced sleep quantity/quality vs. younger, healthy individuals…so it’s a relevant question. Unsurprisingly, these older adults are also at a greater risk for losing muscle mass.

The knowledge that exercise can help prevent the drop in MPS during sleep restriction may have application to situations where sleep might be involuntarily (or voluntarily) curtailed due to jobs, travel, etc. Using exercise as a countermeasure against sleep restriction could be a prescription for at-risk individuals.

While short term sleep restriction isn’t likely to significantly change muscle mass, accumulating sleep loss over time might. For this reason, getting enough sleep should be a priority. But…if proper sleep must be neglected, than perhaps a quick bout of high-intensity exercise is just what the doctor ordered.

Reference

Saner N. et al. The effect of sleep restriction, with or without high‐intensity interval exercise, on myofibrillar protein synthesis in healthy young men. The Journal of Physiology. 2020.

PhD candidate at the University of Florida — Science writing with a particular focus on exercise and nutrition interventions, aging, health, and disease.

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