Sometimes, when I wake up quickly directly from a dream, sensations or emotions from the dream can still be felt. I have heard many stories if people who have felt pain in a dream, only to wake up and still feel the pain. I have personally had dizziness, goosebumps, nausea and a lump in my throat carry over from a dream. It hit me while I was trying to sleep past night: These must be reflexes that aren’t affected by SP.
When we are in REM sleep, almost every muscle in the body is relaxed and paralysed, except the eye muscles. For an impression in a dream to have an effect on the physical body, the physical reaction can’t be affected by this paralysis.
It is very common to wake up from being startled in a half-sleep dream. I don’t know if we are already in sleep paralysis at that point, but the falling/slipping sensation in the dream certainly makes the body react. If it could be proven that we are in SP when this happen, it would also be proof for the fact that the startle reaction isn’t affected by SP.
A while ago, I had a very powerful dream where I heard music, which made all my hairs stand up from awe. When I woke up, I was covered in goosebumps. This was a very powerful dream and definitely REM sleep. The tiny muscles that control our hairs can’t be affected by SP.
Many people have reported that erotic dreams result in sexual arousal that is noticed when they wake up. This must mean that the muscles that are responsible for sexual arousal aren’t affected by SP.
I have woken up crying from very emotional dreams, some of them lucid, which would mean to me that they are definitely from REM sleep. Sometimes, my face has been so wet that I have obviously been crying while I was still sleeping. I don’t know exactly which mechanism in the body is responsible for crying, but it must be unaffected by SP.
Now I wonder which physical reactions and effects you have experienced while waking from a dream. Waking from a lucid dream is one way to make sure that it was a REM dream and that we would usually be in SP at this point.