Calisthenics refers to a type of exercise done without the use of machines, weights, or other apparatus. Calisthenics are done to strengthen and build muscle tone and flexibility. The exercises are meant to use the body’s natural resistance for toning and strengthening muscles and are typically performed in a series of repetitions. Sit-ups, push-ups, squats , jumping jacks and leg lifts are examples of calisthenics. Calisthenics are the exercises that make up the bulk of any gym class, as nothing is needed but the body. While calisthenics is loosely associated with gymnastics and dance, there is no tumbling and little coordination involved. Calisthenics performed over a period of time builds muscle strength and endurance, and thus is often incorporated into athlete’s workout routines as well as acts as an integral part of boot camp training.