I told her good choices for aerobic exercise during pregnancy include brisk walking, stationary bicycling, swimming and aerobic exercise designed especially for pregnant women. I helped Nancy design an exercise program that would work for her. Some women exercise for muscle strength. To strengthen a muscle, there has to be resistance against it. There are three different kinds of muscle contractions isotonic, isometric and isokinetic.
Isotonic exercise involves shortening the muscle as tension is developed, like lifting a barbell.
Isometric exercise occurs when the muscle develops tension but doesn't change its length, such as pushing against a stationary wall. Isokinetic exercise occurs when the muscle moves at a constant speed, as when you swim. Cardiac and skeletal muscles cannot usually be strengthened at the same time. Strengthening skeletal muscles requires lifting heavy weights, but you can't lift these heavy weights long enough to strengthen the cardiac muscle. Weight-bearing exercise is the most effective at promoting increased bone density to help avoid osteoporosis.