I’m curious as to where the perception of ballet dancers as being “ without obvious muscularity” comes from. Perhaps the person on the street who doesn’t watch much, or any, ballet? Because anyone who watches ballet or does ballet will tell you that ballet dancers — both male and female — are muscular. They have obvious muscularity, though in an extremely toned but not chunky manner.

Rick Guest did a brilliant collection of portraits of ballet dancers, mostly from the Royal Ballet. Look at these and tell me if you can still say that ballet dancers do not have obvious muscularity: http://dancetabs.com/2015/12/what-lies-beneath-a-book-of-dancers-portraits-by-rick-guest/

Balanchine is also known for his strong views on ballet — but he is just one person in the ballet world and certainly his opinions should not be taken to be representative of the entire community as a whole.