Achilles tendon

Meh.

Just wondering whether or not the cause of this might have been me learning to skid fairly recently- on 49/15.

Like anyone new to skidding I did it rather a lot, and I pull up with my right foot after moving my weight forward.

So thinking about what Prime Heretic said it might be that this caused a rotating twisting action with a fair amount of energy behind it as I was skidding a high gear?
Sounds very plausible to me, when i was learning to skid a few weeks back i got a bit of a saw calf and noticed my shoes (spds) were reaching maximum float, i find that i get a fair bit of stress put on my tendon when pulling up with that foot. . .