Thanks, yeah suppose that makes sense about the muscle working hard then not. Just before the part where it happens I pedal up a good long hill so sound about right.

Last time when I felt it starting I took my foot off pedal punted my heel down and pushed my leg down hard. That seemed to help and stopped the cramp starting properly.

The last time I got the cramp properly my calf hurt for a few days after but that was unusual as usually once the cramp goes its business as normal