The proper way to do sit-ups. Don't do sit-ups with your feet hooked under a chair or some other object. The flexor muscles in your hips (iliopsoas) must work harder than your abdominal muscles when your feet are anchored. Instead, place your feet on the floor and try to hold them still.

Don't exercise on an empty stomach. Pregnant women in their last trimester should snack on an apple or a piece of toast 30 minutes before exercising. If they don't eat before working out, their blood sugar levels could drop drastically and possibly harm the fetus.

Two types of exercise are better than one. A recent study of men and women ages 60 to 80 reported that they can increase their aerobic capacity by combining aerobic exercise with weight training. Those who mixed the two workouts for 10 months could exercise at higher intensities on exercise bicycles, treadmills, and stair climbers than those who didn't.

To make your walking workout more strenuous, include some hills in your route. If your walk up a 4% grade, you'll burn approximately 35% more calories than when walking on level terrain at the same pace.

If you hold a stretch for any less than 10 seconds, you might as well not do it. Because that is how long it takes before ligaments and muscle fibers loosen.