About 35 years ago, I snapped my left Achilles tendon, not a biking accident; my forefoot just slid off a tall step I was sort of jumping up onto. I had surgery and was in a cast for 8 weeks. So sort of the same thing. I rehabbed it both in the gym and on my rollers. On my rollers, I did quite a bit of one-legged pedaling. I did intervals of up to 2 minutes, same gear both sides, and to exhaustion both sides. That was an easy way to keep track of progress. In the gym, I did one-legged work where I could, like on the leg sled, back machine, single-leg deadlifts, one-legged calf raises, whatever I could think of. Today, that left calf is still smaller than the right, but it's just as strong. I still do some one-legged work in the gym and the one-legged pedaling.
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Results matter