Arnold Schwarzenegger used to sleep 6 hours and he's quite well now and also he gained slme muscles. I have 14 hours night shifts and need to go to gym. How can I manage 8 hours sleep? No way but 4.5 or 6 can be good I think. Just better not to wake up in the Delta phase.
There are sleep cycles but there's no such thing as a REM cycle...
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