This is purely anecdotal, but when necessary leg strength can be maintained by nothing but calf raises.
Just stand there regularly and do high rep standing calf raises. There’s no need to stand on a block of some sort to allow the stretch.
I once took a year and a half off where the only leg work I did consistently was high rep calf raises.
When I got back to the gym my leg strength had maintained just fine.
What exactly had I done during the layoff? 100 calf raises a day.
Now I didn’t start off doing it in one set, it’s smarter to start with multiple sets of 20 or 25, but the benefit lies in the higher reps 50 a set minimum, but 75+ per set really giving the feeling I’m about to describe.
When you get to 75+ reps per set you’ll feel a pump running up your posterior chain.
You’d think this is an isolation exercise, but in the higher reps it isn’t.
The pump will run up your calves into your hamstrings and then into your glutes.
Somehow your body is firing muscles in a pattern similar to a weightlifting triple extension.
Why this is I’m unsure of, but I know it’s the sensation I feel, and the experience I’ve had.
Maybe it’s because of the insertions in your legs, or maybe it’s due to the body’s inclination to fire muscles in a natural pattern during calisthenics. Whatever the reason it works.
-J