For the greatest overall health benefits, experts recommend that you do 20 to 30 minutes of aerobic activity three or more times a week and some type of muscle strengthening activity and stretching at least twice a week. However, if you are unable to do this level of activity, you can gain substantial health benefits by accumulating 30 minutes or more of moderate-intensity physical activity a day, at least five times a week.

If you have been inactive for a while, you may want to start with less strenuous activities such as walking or swimming at a comfortable pace. Beginning at a slow pace will allow you to become physically fit without straining your body. Once you are in better shape, you can gradually do more strenuous activity.

Any increase in aerobic activity is good for you. Studies show that a brisk walk for even one to two hours a week (15 to 20 minutes a day) reduces your risk of having a heart attack or stroke, developing diabetes, or premature death. Weight-bearing aerobic exercise can also strengthen joints, and improve bone strength.

1: Daily physical activity can help prevent heart disease and stroke by strengthening your heart muscle, lowering your blood pressure, raising your high-density lipoprotein (HDL) levels (good cholesterol) and lowering low-density lipoprotein (LDL) levels (bad cholesterol), improving blood flow, and increasing your heart's working capacity.

2: Heightened sensitivity to insulin is attained.

3: Regular weight-bearing exercise promotes bone formation and may prevent many forms of bone loss associated with aging such as Osteoporosis.

4: Bones thicken and loss of calcium slows.

5: Physical activity helps to reduce body fat by building or preserving muscle mass and improving the body's ability to use calories. When physical activity is combined with proper nutrition, it can help control weight and prevent obesity, a major risk factor for many diseases.

6: By increasing muscle strength and endurance and improving flexibility and posture, regular exercise helps to prevent back pain.

7: Regular physical activity can reduce blood pressure in those with high blood pressure levels. Physical activity also reduces body fatness, which is associated with high blood pressure.

8: By reducing body fatness, physical activity can help to prevent and control noninsulin-dependent diabetes.

9: Regular physical activity can improve your mood and the way you feel about yourself. Researchers also have found that exercise is likely to reduce depression and anxiety and help you to better manage stress.

10: Heart muscles become stronger and blood is pumped more efficiently.

11: Regular exercise can leave you feeling energized and looking better, which may have a positive effect on your sex life. But there's more to it than that. Exercise improves your circulation, which can lead to more satisfying sex. And men who exercise regularly are less likely to have problems with erectile dysfunction than are men who don't exercise, especially as they get older.

12: Heart rate and resting heart slow down.

13: Flexibility is increased.

14: Exercise stimulates various brain chemicals, which may leave you feeling happier and more relaxed than you were before you worked out. You'll also look better and feel better when you exercise regularly, which can boost your confidence and improve your self-esteem. Exercise even reduces feelings of depression and anxiety.

15: Digestion and elimination is improved.

16: Regular exercise boosts high-density lipoprotein (HDL), or "good," cholesterol while decreasing low-density lipoprotein (LDL), or "bad," cholesterol. This one-two punch keeps your blood flowing smoothly by lowering the buildup of plaques in your arteries.

17: Metabolism is increased so that the body burns more calories and body fat decreases.

18: The more intensely you exercise, the more calories you burn and the easier it is to keep your weight under control. You don't even need to set aside major chunks of time for working out. Take the stairs instead of the elevator. Walk during your lunch break. Do jumping jacks during commercials. Better yet, turn off the TV and take a brisk walk. Dedicated workouts are great, but activity you accumulate throughout the day helps you burn calories, too.

19: Enhanced clot-dissolving substances form in the blood.

20: Exercise delivers oxygen and nutrients to your tissues. In fact, regular exercise helps your entire cardiovascular system and the circulation of blood through your heart and blood vessels and work more efficiently. Big deal? You bet! When your heart and lungs work more efficiently, you'll have more energy to do the things you enjoy.

21: A good night's sleep can improve your concentration, productivity and mood. And, you guessed it, exercise is sometimes the key to better sleep. Regular exercise can help you fall asleep faster and deepen your sleep. The timing is up to you but if you're having trouble sleeping, you might want to try late afternoon workouts. The natural dip in body temperature five to six hours after you exercise might help you fall asleep.