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We know that sleep is important for gains, but does that sleep need to be contiguous?
What if we slept in phases, each time waking up after REM sleep, and then going to bed a couple hours later?
Or more practically, sleeping for say 5 hours, and then taking naps throughout the day (making sure the naps last long enough to get us through deep sleep).
Would we get the same benefits, or must sleep be contiguous?
You’ve likely heard of human growth hormone (HGH), a hormone that fuels muscle growth and recovery. Well, this hormone is released during sleep, particularly during deep sleep.
This is a good brief info about sleep and muscle growth
with the references at the bottom.
Usually, you fall into REM sleep 90 minutes after you fall asleep.
Since leucine and growth hormone are the key for protein synthesis and they are released during REM sleep which takes about 1.5-2 hours (Adults can spend up to 20% of their sleep in the REM stage) 2x4hours would also be an option. It looks like at least 3-3.5 hours straight sleep is a must.
Growth hormone promotes growth and repair of muscle tissue, so HGH
release during sleep is crucial for muscle building.[2]
Growth hormone also plays a role in carbohydrate metabolism, affecting
energy supply to muscle. Sleep deprivation may slow muscle growth by
altering supply of energy substrate to muscle.[3]
If deep sleep is interrupted, the release of growth hormone is
halted.[4] Thus, a good night’s rest is crucial for growth hormone’s
benefits to take full effect.
I'm not entirely sure this answers the question. You point out that reaching deep sleep is necessary, and the fourth reference says "thus, a good night's rest is crucial [...]". But the asker assumed deep sleep also during daytime naps. So presumably, we're talking about two scenarios with equal amounts of deep sleep.
@Alec That is true. bantandor did mention that sleeping in blocks (2x4, 3.5 straight sleep) was an option - or more importantly he didn't discredit it. I was hoping for a scientific analysis (or citations) of the difference in benefits. Specifically, is there a significant difference in the impact on gains when sleeping in blocks vs. sleeping like a normal person. But this was the only answer at the time, so I marked it best answer.