Being the weak man that I am, I allowed a friend to talk me into playing squash yesterday. I haven't played squash for about seven years. I played about as well as one would expect given the gap, and the fact that I wasn't very good back then anyway. Unfortunately, I woke this morning with a sense that there was something wrong..... when I tried to get out of bed - and couldn't - I assumed I had suffered some sort of stroke in the night.
Alas, nothing so respectable.
Listening to my body, I conclude that exercise is bad for me. It is a lesson I will not forget.