Top Ten Runner's Mistakes

Running is a cheap and easy exercise. "You don't need anything other than a good pair of shoes and somewhere safe to run," says Dr. Margot Putukian, director of athletic medicine at Princeton University. And with all the health benefits of a good jog, it's no wonder that nearly 12 million Americans do it regularly and more than 37 million lace up their track shoes at least once a year. Running helps prevent obesity, diabetes, hypertension, high cholesterol and heart disease. It helps with mental health while burning between 450 and 1,400 calories an hour, depending on a runner's speed and size. Just 30 minutes of cardiovascular exercise three times a week can increase longevity by six years, says Dr. Tyler Cooper, a physician at the Cooper Clinic in Dallas and co-author (with his dad, Dr. Kenneth Cooper) of the new book "Start Strong, Finish Strong."

But even if running seems like the most intuitive exercise you can do, runners still develop some ill-advised habits that can cost them when it comes to their health. Here are 10 of the most common mistakes and how to avoid them:

1. Footwear
Folly Wearing old shoes, or ill-fitting ones, can lead to problems with your feet, ankles and knees. Replace your shoes every 500 miles or so. Cooper recommends buying two pairs of shoes and alternating. "It gives the shoe time to rebuild the cushioning and expand back," he says.

2. Overdoing It
Don't be a weekend warrior. Many people fall victim to the too's—"too much, too soon, too hard," says Dr. William Roberts, medical director for the Twin Cities Marathon in Minnesota. Start slowly, running half a mile, then walking half a mile—or walking a block, then running a block. And take at least one day a week off. People who do too much too quickly can develop musculoskeletal problems like tendinitis in their heels or knees. For physical fitness, just a half hour five times a week is plenty.

3. Skimping on the Stretching
It's most important to cool down after the run. Stretching before the run is OK too, but do it lightly and avoid the "bouncy, ballistic" stretching, says Putukian. Instead, do a "slow, steady stretch," she says.

4. Postponing a Doctor Visit
"People are notorious for trying to run through their pain," says Cooper, a five-mile-a-day runner who admits that he falls into this category himself. "Be proactive. Go to the doctor before it gets bad. A lot of times just putting some orthotics in your shoe can change everything." If you don't take care of a problem, you may end up with chronic tendinitis or shin splints.

5. Not Cross-Training
"Runners are using one continuous motion," says Cooper. Ideally, runners should alternate sports to use different muscle groups and lessen the risk of injury. "It gives your body time to recover from certain movements," says Cooper, who breaks up his runs with occasional swimming days. Putukian advises: "Mix it up a little with different forms of exercise; biking, using an elliptical machine or a stair machine, walking, and some strengthening exercise. Cross-training will make it easier to stay healthy, have fun and avoid the pitfalls of overuse injuries."

6. Sticking to the Same Pace
"Varying your speed, once you get into a regular running habit, is a good thing to do," says Cooper. "Increase the intensity and then cut back." It prevents monotony and is good conditioning. It's also better for your heart. "Some people get into a habit of jogging, and they don't get their heart rate up enough," says Cooper. To get the best cardiovascular benefit, run at 70 to 85 percent of your predicted maximum heart rate. (To calculate that number, subtract your age from 220—and then multiply by 0.7 and 0.85.) You can run with a heart-rate monitor, or simply count your pulse for six seconds and multiply it by 10.

7. Hitting the Pavement Too Often
"Concrete is the hardest thing on your knees," says Cooper, who prefers dirt roads or tracks because they "take some of the tension off of the joints. When you hit the concrete, it doesn't give." Grass is good too, though runners need to watch for holes.

8. Accepting Boredom
"If running becomes a chore for you, find something else you like—or find someone to do it with you," says Cooper.

9. Skimping on Safety
Don't put your iPod on too loud. It's important to be able to hear cars—or someone calling to you for help or to warn you of danger. For early-morning or twilight runs, wear a reflector vest so you're visible.

10. Not Hydrating
It's important to drink fluids to replace what you lose in sweat. "But you don't want to overhydrate with just water alone," says Putukian. "Your sodium levels can drop to dangerously low levels and can be life-threatening. Symptoms of low sodium include feeling lethargic, dizzy, or nauseous." One good option is to use a sports drink that provides some glucose along with electrolytes in a solution that's not too concentrated. Avoid soda, coffee and juice, as caffeine is a diuretic and can add to water loss, and the higher concentration of glucose in juice and soda can be difficult for the gastrointestinal tract to handle.