The beauty credits Piela with getting her into boxing. “We start with jump rope — there’s no better hope—there’s no better way to slim down legs — and we end with ballet-inspired floor exercises… in the middle, we box,” said the trainer and former pro fighter, who owns the Gotham G-Box gym in New York City. 

Hadid, 26, has said she values the psychological effects just as much as the physical. “When you’re boxing, you get so into it mentally that you kinda forget what’s going on, you forget that you’re working out.”