Coincidentally I ran a 10K yesterday and early in the race I felt the "catch" trying to kick-in. It was an uphill course and I worried that if it really did catch, I would be out of commission for the race and at least one week.

I kept running and focussed on keeping my toes back and striking with my heel, for all intents and purposes keeping my calf in a stretched position as much as possible. It eventualy went away and I dodged a fairly signficant delay in my training.

I've thought about this and wondered why did it want to do this in a race when I've trained for a couple of months with no issues. Two things:

1. Race pace - I was pushing harder than normal - earlier in the run than normally.
2. Different surface - I do almost all of my training on trails in a park near my house. The race was a considerably harder surface than my training surface.

I'm thinking that number 2 above is the main culprit, and it has to do with the jarring of the muscle on the harder surface more than the pace of the run.

Anybody else have simlar observations?