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.
For best results in the gym, you'll want lots of slow-wave (deep) sleep. You get most of that in the first 3 cycles ... but taking care of your brain (emotions) is important too, and most of that happens in cycles 4 and 5.
Jones Private