Cardiorespiratory endurance is reflected in the sustained ability of the heart and blood vessels to carry oxygen to your body's cells. Excellent "aerobic" activities for building endurance include brisk walking, running, in-line skating, swimming, cycling, rowing, and aerobic dance.
Recommendation: To gain health benefits, 30 minutes of moderate physical activity over the course of most days is enough. For greater cardiovascular benefits, you need to perform moderate- to high-intensity aerobic exercise (at 60 to 90 percent of your maximum heart rate) three to five times a week, with each session lasting 20 to 60 minutes, in addition to warm-up and cool-down activities.
Muscular fitness consists of strength -- the force a muscle produces in one effort -- and endurance -- the ability to perform repeated muscle contractions in quick succession.
Recommendation: Perform moderate-intensity resistance workouts twice a week lasting at least 15 minutes per session, not counting your warm up and cool down.
Flexibility refers to the ability of the joints to move without discomfort through their full range of motion. This varies from person to person and from joint to joint. Good flexibility is thought to protect the muscles against pulls and tears, since short, tight muscles may be more likely to be overstretched.
Recommendation: Try to perform flexibility exercises three to four times a week.
Before you begin an exercise program
If you over 40 and sedentary, the American College of Sports Medicine recommends that you consult your physician before beginning an exercise program and have a pre-exercise medical and physical examination. Your physician may recommend that you take a special exercise stress test.
If you are younger, consult with a physician first if you have any risk factors for heart disease (such as recurrent chest pain, high blood pressure or cholesterol levels, smoking, or obesity). Also, contact your physician if you have cardiovascular or lung disease (or symptoms that might suggest this).
Ten exercise guidelinesExercise can be so involving that it's easy to be carried away by the joy of the moment and to forget certain measures that can reduce risk of injury. The following exercise guidelines will protect you from injury and help make exercise more enjoyable.
- Set realistic exercise goals. Set goals that you not only know you can achieve., but that are specific, not vague ("I'll cycle twenty miles this week," not "I really should get more exercise this week.").
- Whatever activity you pursue, don't overdo it. The most common cause of injury is exercising too aggressively -- the "too much, too soon" syndrome. Start any new exercise at a relatively low intensity and gradually increase your level of exertion over a number of weeks. Use the "10 percent" rule: In general, don't increase your training load -- the length or frequency of workouts, the intensity, or the distance -- by more than 10 percent a week.
- "No pain, no gain" is a myth. Exercise should require some effort, but pain is a warning sign you are foolish to ignore. If you have continuing pain during an exercise, stop and don't continue unless you can do so painlessly. (If the pain occurs in the chest or neck area, you should contact your physician immediately.) General muscle soreness that comes after exercise is another matter: It usually indicates that you are not warming up sufficiently or that you are exercising too long or strenuously.
- Control your movements -- if you can't, slow down. Rapid, jerky movement can set the stage for injury. As you move your limbs, keep the muscles contracted and move them as if you are pushing against some resistance.
- Watch your form and posture. In most activities, stress can result from poor form. Keep your back aligned (abdominal muscles contracted, buttocks tucked in, knees aligned over feet). This is particularly important when jumping or reaching overhead.
- Don't bounce while stretching. This "ballistic" stretching can increase the chance of muscle tears and soreness. Instead, perform "static" stretches, which call for gradually stretching through a muscle's full range of movement until you feel resistance. This gradually loosens muscles without straining them.
- Use good footwear. Wearing improper or worn-out shoes places added stress on your hips, knees, ankles, and feet -- the sites of up to 90 percent of all sports injuries. Choose shoes suited to your activity and replace them before they wear out.
- Avoid high-impact aerobics. Most aerobics instructors and many students suffer injuries to their shins, calves, lower back, ankles, and knees because of the repetitive, jarring movements of some aerobics routines. Substitute the marching or gliding movements of low-impact aerobics for the jolting, up-and-down motion of typical aerobics.
- Warm up and cool down. Slowly jog for five minutes before your workout to gradually increase your heart rate and core temperature. Cool down after exercising with five minutes of slower-paced movement. This prevents an abrupt drop in blood pressure and helps alleviate potential muscle stiffness.
- Replace fluids lost through sweating. This is particularly important in hot weather, when you can easily lose more than a quart of water in an hour. Neglecting to compensate for fluid loss can cause lethargy and nausea, interfering with your performance. Even if you don't feel thirsty, it's important to drink at regular intervals when exercising. (Thirst is satisfied long before you have replenished lost fluids.)