Do you meditate regularly?
Yes. Throughout the day.
Have you ever had physical sensations, while you were in the midst of a session?
Yes, regularly. Vouthon cited the Buddhist term Piti. This gives a brief summary of the types of rapture or ecstacy that comes with it in their classification system.
https://en.wikipedia.org/wiki/Pīti#:~:text=Pīti in Pali (Sanskrit: Prīti,to the calmness of sukha.
Last night while I was sitting out on my porch (my usual place), I felt my brain do a front flip in my skull, and then felt a wave of pleasure/warmth run down my neck to my toes/fingers.
That's an interesting description, your brain doing a 'front flip'. Can you elaborate? The wave a pleasure through the body I understand, but not the brain doing a front flip? Dizziness? Or something more like a sudden, spontaneous 'release' or transcendence of mind?
It was interesting to say the least, even if this broke my concentration and I was unable to get back into the groove of my meditations, after the fact.
I practice qigong and taijiquan. This is all about energies and directing them. As sensations as you describe move through you, this is because you are learning to release all tensions in your body. Rather than being distracted by them, you follow them and let them take you. Rather than trying to analyze them, let them direct you. They are part of the meditation. They can take you much deeper, to the point of absolute stillness of mind, where your breath and the world around you are connected and alive, not separated by what's going on inside vs. what's going on outside, but rather an energetic whole.
It's basically stepping outside of that isolated 'thought-world' swirling around in our heads, out into Reality, like stepping through a door that was never really there, or pulling back the drapery and letting the light into the room. You're not finding something that was missing. You allowing what was there the whole time to come into full awareness. It was yours the whole time.
As this becomes known to us as part of the reality of who we are, you can learn to pretty much enter that state at will through basic mindfulness practice, stopping letting discursive thought, that constant dialoguing with ourselves inside our thought-world, which leads to tension and stress, blocking those flows of natural energies, or Qi.
A simple technique I use is to periodically doing a body-scan from the head down to find where I am holding tension, like in the neck, or the low back, or shoulder, etc. When I become aware of that, it almost always ties directly back into something I am letting my mind be preoccupied with, and not being present in the moment. Once that has been made aware of, I let go of doing that to myself with my mind, and release the tensions from the body through breath and visualizations. Then, that energy, that warmth, that rapture, that bliss can move again.
I used to do only a sitting meditation, but found that physical movement, for the sake of groundedness was also necessary. Being grounded is incredibly important, otherwise the mind is like a balloon being tossed about by any and all movements of energies, which only leads to anxiety and stress.
One last thing to share. It might be helpful to understand the different levels or stages of meditation that can happen. This is a great Q and A about those state-stages, and he covers what are generally recognized as the psychic, subtle, causal, and nondual stages. He describes the sensations associated with each of these, for your reference.
STAGES OF MEDITATION
