This group of classic Pilates moves, collectively known as the Series of Five, is the perfect addition to any workout. Take it from Lisa Corsello, founder of Burn Pilates and wholehearted Series of Five fan. "It is my favorite set of exercises," she explains. "Whenever I work out, I do a Series of Five. It's really focused on the core, but your arms and legs are moving in all these different directions, which makes it much more challenging to hold your position."