“It’s funny how raw a child’s reaction to something is. There’s no filter. It’s just really physical and that’s what I love about it,” said Matt Gilmour, creative director at marketing agency Saatchi ...

Slow-motion strength training is easier on joints and connective tissue, which may reduce risk of injury. The high-intensity workout is just 20 minutes, once a week. Seniors swear by the routine, but ...