With Proform PFPKB0513 Kettlebell training is challenging, efficient and requires only one piece of equipment for versatile, dynamic workouts. It's a great way to increase endurance, improve balance and build strength. Developed by Russian strongmen in the early 1700s (with links back to Ancient Greece), kettlebells have been recorded to burn 20.2 calories per minute. That means in a typical 20-minute workout, you could burn up to 400 calories. That is equivalent to running a 6-minute mile pace or cross-country skiing uphill at a fast pace. The genius of the kettlebell's quick calorie burning is the total-body movement-which is done at a fast interval rate.