Holy shit, you want a serious workout for strengthening the calves?
After messing up my knee, the PT told me that since I danced tango in high heels, I should do single-leg heel raises (other foot on a chair) holding 5 pounds in each hand, 25 reps.
One of my tango teachers says to do heel raises, counting to 6 up and 6 down.
So, I just did…I don't know, maybe 10 reps? however many I could manage… one-leg, 5 pounds per hand, 6 count up, 6 count down.
WOW