Yes those are ballet slippers you see on muscleman Jack LaLanne in the great old clips of his workout shows.His official blog addressed the topic in November:
Posts tagged: Jack LaLanne
Television pioneer and fitness preacher Jack LaLanne passed away Sunday in California. He was 96 years old.
Jack LaLanne was a fixture on morning TV for decades, doing push-ups and squat thrusts and telling viewers to eat right!, with a peppy, you-can-do-it delivery. His official site features several videos of classic episodes of The Jack LaLanne Show.
Or, you can have a little sample here: