Good judgment comes from experience, and experience comes from bad judgment. This old saying is especially true for exercise, in which bad judgment can lead to aches, pains, and injuries. Bad judgment can also waste time and effort. Therefore, being aware of the pitfalls that plague novice and seasoned exercisers can help prevent problems and help you maintain a comfortable and consistent program.

Depending on your exercise goals and the intensity of your training, some of the common pitfalls listed below may apply to your situation now. Others won't be important until you have considerable training under your belt. Consider those that apply to you and adjust your program accordingly.

Technical Fouls
Less-than-choice choices. Making the right exercise choice can make all the difference. Weight-bearing exercises such as walking and jogging are great for most of us, but they can be too demanding for those who are overweight or have muscle, bone, or joint problems like arthritis. Exercises with barbells can also stress joints, especially the elbows and shoulders.

Alternatives include non-weight-bearing exercises (in which your weight is supported), like bicycling or exercising in the water. Also, weight machines or dumbbells may reduce joint stress and allow you to continue weight training without pain.

Troublesome technique. Exercise technique is critical, even for exercises that you take for granted, like walking. When increasing the pace of walking, for example, it's natural to take longer strides. But this can overstress your shins. Proper technique entails taking more rapid strides without increasing their length.

A small breath of air. Novice exercisers tend to breathe rapidly and shallowly because it feels right. But with this type of breathing, oxygen does not make its way to the depths of the lungs where it's needed. This contributes to a sense of breathlessness. Instead, consciously take longer and deeper breaths.

Intensity Trouble
Body not ready. Vigorous exercise is one of the most stressful challenges your body can face. If you are healthy, your body will adjust to the demands, and such adjustments increase fitness. But an unhealthy body can be overwhelmed by exercise. See your doctor to make sure your body is ready for the challenge.

Feel the burnout. When you improve to the point where, say, a 5-mile run is fairly easy, don't assume all is well. Your abilities and drive may inspire you to keep adding to your workload. In this case, even small and slow increases can add up and become too much.

If you find yourself dreading your exercise sessions or dragging yourself through the day because of exhausting workouts, you may be overtraining--doing more exercise than your body can tolerate. If so, cut back to where your workouts are comfortable again and you look forward to them. Take a few days off completely and then return at a much reduced level.

'No pain, no gain.' Athletes are taught to train hard and to overcome pain. But years of training are required to withstand high-intensity workouts. If you are a competitive athlete, you may have no choice but to train as hard as the coach demands. But everyday exercisers should cut back when they feel pain.

Damage Control
Not easing in and out. Take time to warm up and ease into exercise. Even if you only walk or do other forms of mild exercise, your body needs an adjustment period. Start with a slow, comfortable walk before progressing to faster speeds.

If you choose more demanding exercise, the warm-up phase should be longer and more involved and include a variety of stretching exercises. At the end of a workout, don't stop abruptly, but rather slow your pace gradually until you quit. Then stretch again.

Leave it for weekends. Many people use sports as a means of getting in shape. They push themselves on weekends in demanding events like basketball that can stress the body to its limits. This "weekend warrior" approach is backward. Instead, get in shape first so you can enjoy sports safely. This is especially important if you do not participate regularly.

No rest for the workout. Vigorous exercise takes a toll on the body, and not resting completely between workouts can spell trouble. This is especially true as you get older, because your body may need more time to recover. Get as much sleep as your body needs every night.

Gear Choices
Unclear on gear. Good exercise gear is designed to reduce stress and help you avoid injuries. Jogging and walking shoes are designed to provide support and absorb shock. For exercising in the heat, proper clothing lets excess heat escape from the skin to minimize overheating. In the cold, certain material wicks moisture away from the skin, helping you stay dry and warm. Such training aids can be expensive, but going the cheap route could ultimately cost you big bucks at the doctor's office.

Ecologic illogic. Heat, humidity, and high altitude stress the body considerably during exercise. Therefore, don't attempt to accomplish as much as you would under more ideal conditions. In hot weather, drink enough water to make your urine clear.

Cold and wind can cause frostbite if your skin is unprotected. Your ears, fingers, and toes are especially vulnerable.

Unkind surfaces. If you walk or jog, the surface you choose to exercise on is important. User-friendly surfaces will reduce the impact shock. Grass and smooth gravel are friendly, whereas cement (as on sidewalks) is brutal. Asphalt is better than cement, but not as good as grass. The surface also must be even and predictable.

Great Expectations
Fat fiction. Exercise can help you lose body fat, but you need to know two facts. First, you cannot remove fat from specific areas of the body with specific exercises (a concept known as spot reduction). Sit-ups won't reduce your waistline, for example, because fat burned as fuel during exercise is drawn from fat stores all over the body.

Second, a bout of exercise burns fewer calories than you might expect, so you probably won't shed pounds without a low-fat and moderate-calorie diet. A 1-mile brisk walk, for example, will burn about 100 calories for an average-sized man and about 85 calories for an average woman. Contrast that with a 500-calorie deluxe cheeseburger.

Fair-weather exercise. Regardless of your goals or the type of exercise you choose, little will be accomplished by sporadic exercise. The key to success is consistency. On occasion you won't have time to exercise as much as you would like. On those days, it's important to do something, no matter how small. A little exercise performed daily will produce much greater results than sporadic, lengthy workouts.