How to improve as a runner

[Bierzo Baggie]

He said he never treated fell-runners because each step was different off-road; it was always road runners because of the persistent, repetitive impact on tarmac which would magnify biomechanic issues and stress specific muscles.

Yep. I've never ever got into running science but that sounds logical. I've got a bit obsessive about this over the years to the extent that if I'm running along the road I'll instinctively veer towards grass verges or even run along ditches.

I'll second what Sweder says as well. I thought it was running on tip toes which strengthens your calf muscles. Or am I missing something?

Bad luck regarding the injury. Fast, explosive races will always run the risk of injuries, especially if you're pushing yourself as hard as you can.
Hope you're back on the hills as soon as possible!