Recently I read a forum post by a piano teacher (and life coach), who said that it’s hard to leave old habits behind because of muscle memory. I agree with him that there is muscle memory involved, but at least as far as old habits in sitting, there’s also the panic of the suffocation response. Sooner or later, I begin to feel like the posture is affecting my ability to breathe, and there’s a certain anxiety associated with that. Knowing about the suffocation response helps me to realize how much I need to emphasize relaxation, if I want to overcome old habits.
On the subject of “aching-legs Buddhism”, I finally attended a five-day sesshin last fall, at Jikoji. I discovered that at least for the sesshin I attended, they were sitting mostly a 40-minute sitting followed by 30-minute sitting, throughout the day.