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. Back (upper) You can’t see your back without a lot of effort, but this doesn't mean you shouldn’t train it. Back exercises consisting of both back stretching and back strengthening is very important to your health and overcoming back pain. Exercise Instructions Step 1 Start on the floor with your knees bent, your back pressed firmly on the ground and your arms at bent at your sides. Step 2 Starting with your elbows tucked in towards your ribcage, extend your arms and try to touch them over your head. Step 3 Try to keep your elbows and wrists in contact with the floor throughout the entire range of motion.