OK, after running or walking for an hour or so I sometimes get a pain in the top of the calf muscle just below the knee (one leg only, always my right). I can usually continue the run or walk, but it becomes more uncomfortable as I go on.
The pain in the top of the calf becomes severe if I try to fully bend my knee, for example by doing a quad stretch (the one you do standing on one leg). When the leg goes back down the pain goes away. This is curious, since the pain gets worse when the muscle is apparently relaxing.
A hamstring/calf stretch seems to help slightly, but never really eases the pain felt during the quad stretch.
It is generally fine again by the next day, with a full on quad stretch not giving any discomfort.
This only happens sometimes. Certainly not every run/walk.
Any ideas anyone?