exercise and aneros.

Early in my Aneros practice I'd frequently have a muscle cramp or spasm. Suggested by rumel, mild stretching of skeletal muscles, before the sessions, put a stop to serious cramps.

Three back stretches I find useful to relax and on occasion also induce mild pleasure waves, up spine and down back of legs are:
(1) Sit with knees slightly bent and legs pulled towards your chest and just allow yourself to gradually flop over so your head is sinking towards the floor between your legs, breathe from your belly slow and deep and let your neck and upper spine stretch into the forward bend.
(2) Sit with legs outstretched together, raise arms and bend forward with intention of hands grasping toes and again gradually stretch into that position with deep, slow belly centred breathing - the forward bend - Paschimothanasana in yoga.
(3) Stand and very gradually let your neck, then upper spine and then finally lower spine bend forward so your head moves towards your knees and your hands eventually clasp back of legs - again breathing slow and deep from belly. - the standing forward bend - Pada Hasthasana in yoga
For all stretches don't force yourself into the position, just let gravity gently guide you into it and relax.

Lately I find that I quite enjoy stretching at the start of sessions with the smaller models (I find it a bit uncomfortable with the Progasm inserted). This actually led to me inserting the aneros earlier in my session than I normally would have - before even lying down I decided to insert it and walk from the bathroom to my bed.

I ended up smoking a cigarette with it inserted and then performing a few standing hamstring stretches. When I got to the bed a performed a series of back stretches as well.

Results were that I got spasms during the stretches the very second I began to focus, and my session afterwards was quite intense overall.

I like what hapticbear recommends - I may do that very routine this evening.