MUSCLES ENGAGED Shoulders The shoulder is the most movable joint in the body. However, it is an unstable joint because of the range of motion allowed. This instability increases the likelihood of joint injury, often leading to a degenerative process in which tissues break down and no longer function well. Glutes Gluteal Muscles (Glutes) are one of the strongest muscles in the body and are the connecting point between your legs and back muscles. Glutes are used in a variety of actions from moving the leg to extending and rotating the hip, as well as extending and rotating the trunk of the body. Exercise Instructions Step 1 Start in a kneeling position with your hands under your shoulders and your knees hip width apart. Step 2 Slowly extend one arm and the opposite leg while keeping your back flat and core tight. Step 3 Return your arm and leg back to the starting position and repeat on the other side.