The American College of Sports Medicine recommends that people struggling with obesity start with low-intensity aerobic activity when beginning an exercise program. Aerobic exercise includes any rhythmic activity that uses large muscle groups and elevates the heart rate for a sustained period. Though the principles of aerobic exercise are the same for everyone, someone who is obese may find certain forms of aerobic exercise unrealistic. High-impact activities, like running and jumping, may be uncomfortable or stressful to joints. Walking, swimming, cycling or using an elliptical trainer might be better choices for starting out.
When walking, one foot is always in contact with the ground. This makes the impact of walking much lower than that of running, where both feet leave the ground at the same time. People of almost any fitness level can find a comfortable walking pace to participate in this low-intensity aerobic activity. On a 0 to 10 scale, ranging from extremely easy to extremely hard, walking should feel somewhat easy with an intensity rating of about 4. Walking at this intensity 4 or 5 days a week for 30 to 60 minutes will meet the target for aerobic exercise suggested by the ACSM.
Obese people frequently suffer from secondary conditions, such as arthritis, that affect mobility. Obesity itself may be an impediment to mobility. Mobility limitations can make it difficult to exercise aerobically. A comprehensive review published in June 2011 in "BMC Musculoskeletal Disorders" concluded that people who are unable to exercise on land due to mobility limitations may be able to successfully participate in aquatic exercise programs. The study noted that comparable health outcomes can be achieved with land-based or aquatic exercise programs. Aquatic exercises may include various forms of swimming, pool walking or other rhythmic activities performed in water. The goal of aquatic aerobics is the same as for land-based aerobic exercise: to modestly elevate the heart rate for 30 to 60 minutes 5 days per week.
Cycling engages the large muscles of the hips and thighs without causing excessive stress on the joints of the legs. Cycling is a very effective activity for achieving and maintaining an elevated heart rate. Traditional cycling gets you outside and provides the added benefits of fresh air and changing scenery. Stationary cycling is another option if balance issues make traditional cycling seem daunting. Many seat types are available, and recumbent options also make it possible for most people to find a comfortable means of pursuing cycling as a low-impact, low-intensity form of aerobic exercise.
Once someone is consistently meeting the ACSM target of 5 days per week of 30 to 60 minutes of low-intensity aerobic exercise, she should consider increasing the intensity of aerobic activity. If she has built a solid foundation of walking, she should start to mix in short bursts of jogging. At this point, the body may tolerate slightly higher-impact activities if they're introduced slowly. In the pool, she can introduce new strokes or speed things up a bit to keep it challenging. If the cycling routine is getting easy, she can try adding a few hills. Increasing the resistance settings or working on short bursts of speed on a stationary bike forces the body to adapt and to operate outside its comfort zone.