Ed. James, Practical Training for Running…
“ In long distance running, the front and back muscles of the thigh are used in equal proportions; the former in raising the body at every stride, the latter in propelling it forward. But in the case of running on the toes, the calf of the leg will be the weak part; so much so that no amount of practice will enable some, especially heavy men, to run any distance on their toes. ”
