Re: Seiza and Calves Pain
If you are finding it hard to get up after seiza because your feet/etc. are asleep - it is always a good idea to not go ahead and try and stand up out of instinct right away. That has caused many a twisted ankle or worse. When your feet go to sleep you might find it very helpful to get up on one knee (say your left knee) and then rub the bottom of your right foot on the mat by sliding it back and forth over the surface of the mat. When you feel the blood return to that foot from the circulation you are promoting with the friction you are causing, go ahead and stand up and do the same process with the left foot.
If you are not allowed such time, like when you are a member of the uke pool during a test, and you are plauged by your feet going to sleep, you might find it a good idea to switch seating postures (back and forth between cross-legged and seiza) often.