Ankle Muscles
 

Does cycling strengthen or enlarge the extensor digitorum longus and flexor digitorum longus?

Yes, and it may be an indicator of a circulatory problem, or some local issue causing inflammation. Depending on the degree, duration and whether there's also pain, I'd make a decision whether to chalk it up to idiosyncrasy, or set it up an appointment with my doc, and ride there so he could see it while it's there.

That is a good idea. You have promoted me to think that taking pre and post ride measurements may also be helpful.

There are plenty of variables. For example, chronically swollen ankles may be indicative of kidney issues causing excess water retention. This, in turn, may be caused by drugs, so if this is a new issue, ask yourself what's changed.

If this is about swollen ankles, mine swell every time I retain water ... and my left one swells more because of past issues with my left foot/leg. I burned it to the bone in 2001 and developed DVT in 2009.

In fact, one of the signs of that DVT was a badly swollen ankle and leg.