Regular exercise makes the heart stronger and the lungs fitter, enabling the cardiovascular system to deliver more oxygen to the body with every heartbeat and the pulmonary system to increase the maximum amount of oxygen that the lungs can take in. Exercise makes muscles stronger. Every physical task requires muscle strength and some degree of range of motion in joints. Exercise stretches muscles and joints , which in turn can increase flexibility and help prevent injuries. Exercise increases the body’s level of endorphins , chemicals in the brain that reduce pain and induce a sense of well-being. In addition to its other benefits, regular exercise helps older people remain independent by improving functional ability and by preventing falls and fractures. It can strengthen the muscles of even the frailest older person living in a nursing or retirement home. In addition to recommending exercise for general health and well-being, doctors may prescribe specific exercise plans in some situations. Before elective surgery, doctors may recommend people participate in exercise routines to enhance their recovery from surgery.