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. Quadriceps The quadriceps (quads) are a group of four muscles on the front of the thigh. They allow your knee to straighten and provide stability when standing. Your quads are the most important muscle group for maintaining the ability to stand and to walk independently. Equipment Used Kettlebell The kettlebell is a cast-iron weight (resembling a cannonball with a handle) used to perform ballistic exercises that combine cardiovascular, strength and flexibility training. Sizes may range from 4 pounds (1.8 kg) to 175 pounds (79 kg). Exercise Instructions Step 1 Start on your back while holding the kettlebell in one hand directly above your shoulder. Step 2 Press yourself up on to your elbow, then up on to your hand, bridge up and pass your leg underneath your body. Step 3 Turn your body in to a proper lunge position while holding the kettlebell overhead and stand up.