Sadie Nardini developed Core Strength Vinyasa Yoga, after noticing that many yoga students over-rely and overwork their arms and legs.  A co-founder of The Fierce Club in New York City, she specializes in "kick-asana" workouts.  Nardini is GaiamLife.com's "Core Strength" columnist and has been featured in The New York Times, Yoga Journal and Self magazine.