Aerobic exercise raises your heart rate with continuous, rhythmic movement and, done regularly, will increase your stamina and strengthen your heart and lungs. It should be done 3-5 times per week for at least 20 minutes. Walking is the best place to start, but bicycling and jogging and swimming are good options, too. Swimming is also an excellent choice as part of an exercise program; the water provides resistance, and it also has cardiovascular benefits and can be less damaging to joints than higher impact aerobic exercises.
Beginning an exercise program does not have to be complicated! It is advisable to consult your doctor before you start. Then begin with an easy routine like walking around the block or taking longer walks at the local shopping mall. Starting off with a difficult routine is associated with a higher dropout rate. The goal is to increase physical activity from your current level.