This 45 min class is split between the tread and strength training. The run is designed with intervals similar to that of our Tread on the Mill signature class followed by functional strength training specifically designed to keep you injury free and running strong. Strength training consists of dumbbells, bands, kettle bells and core work. Expect to cover 2-4 miles while building more strength than most. You will efficiently strengthen all muscle groups, maximize calorie burn and increase endurance. Definition of kettlebell : a round weight with a flat bottom and thick handle on top that is used for exercise and weight training.