If you’re like most Americans, your biggest New Year’s resolution was to shed unwanted pounds by eating less and exercising more in an effort to improve your health. Unfortunately, if you’re like most Americans, you probably failed to achieve that goal. Don’t feel too bad. Losing weight is difficult; losing weight in this land of plenty, where most restaurant meals could feed a family of four, is harder still.

In an effort to help Americans lose weight and stay healthy, the U.S. Department of Health and Human Services recently announced new exercise recommendations. They include:

• To reduce the risk of chronic disease in adulthood, engage in at least 30 minutes of moderate-intensity physical activity most days of the week.
   
• To help prevent gradual, unhealthy weight gain in adulthood, engage in about 60 minutes of moderate- to vigorous-intensity physical activity on most days
   
• It’s excellent advice, but many Americans could find their efforts sabotaged by a wide variety of exercise myths, experts warn. These falsehoods — often passed as fact from friend to friend — can cause you to exercise incorrectly and even endanger your health. Following are some common exercise myths and why they’re untrue.

1. Myth: Just do it!

Reality: This slogan from Nike is designed to get armchair athletes off their butts and into the gym. “But it’s not that simple,” says R. Timm Lovins, a clinical exercise physiologist and director of Fitness and Wellness, Oak Hammock, University of Florida in Gainesville. “There are things you need to do before beginning an exercise regimen. Foremost, if you haven’t exercised in a while, it’s a good idea to see your doctor first to make sure there are no contraindications that could make an exercise program dangerous for you.”

2. Myth: No pain, no gain.

Reality: A little discomfort is normal following a workout, especially if you’re incorporating a new exercise, says Lovins. But extreme pain is a sign that you’ve pushed your body too hard. “Exercising to the point of pain causes you to actually lose ground because a painfully sore muscle needs time to rest,” Lovins adds. For best results, exercise with reasonable intensity, and give your muscles time to rest between workouts.

3. Myth: You must exercise continually to gain significant health benefits.

Reality: Not true, says Dr. John D. Kelly, associate professor and vice chairman, Temple University School of Medicine in Philadelphia. “To see significant gains in aerobic capacity, one must exercise at 60 percent to 70 percent maximum heart rate three times a week,” Kelly says. “But if all you want is life extension and low body fat, you need only exercise about 30 minutes a day, and that can be broken up into 10-minute increments — 10 minutes of stairs, 10 minutes of dog walking, and 10 minutes of gardening. You won’t get the gains in aerobic fitness, but you will live longer and decrease your risk of diabetes, hypertension, and obesity.”

4. Myth: You practically have to live at the gym to achieve appreciable gains in strength.

Reality: Also not true. “We now have good literature showing that just one set using barbells or a variable resistance machine two to three times a week will give you a significant increase in strength over a period of months,” Kelly says.

5. Myth: Aerobics are the best way to reduce your body fat percentage.

Reality: Weightlifting is more effective at reducing body fat. “Lifting increases lean body mass, which increases your basal metabolic rate so that you’re burning calories even when you’re not working out,” explains Kelly. “In a recent study, one group of subjects was placed on an aerobic program, and a second group was placed on a lifting program. At the end of the study, the lifting group had a lower body fat percentage.”

6. Myth: Abdominal crunches reduce stomach fat.

Reality: Abdominal crunches help tighten stomach muscles, but cardiovascular exercise or weight training is better at eliminating that unsightly potbelly because it causes the body to burn fat for fuel, explains Lovins. Effective cardiovascular exercises include walking, tennis, and cycling — anything that gets the heart rate up to moderate levels.

7. Myth: Women should avoid weightlifting because it causes them to bulk up like Arnold Schwarzenegger.

Reality: Most women don’t possess adequate amounts of testosterone to develop manly muscles, so bulking occurs only if they’re taking steroids, says Kelly. In truth, weight training is a great way for women to boost muscle tone and decrease body fat. It also helps prevent bone-weakening osteoporosis and decreases depression and anxiety.

8. Myth: Exercise is for young people only.

Reality: “It’s never too late to start exercising,” says Kelly. “In a study at Tufts University, elderly men and women gained appreciable muscle mass in their legs, upper chest, and shoulders from a progressive-resistance lifting program three times a week.” Regular exercise also can help ease the pain and stiffness of mild to moderate arthritis, Kelly adds.

9. Myth: You must join a gym and use a personal trainer to get the most out of an exercise regimen.

Reality: If you have the discipline, a home workout can be just as effective as going to the gym, says fitness guru Greta Blackburn, editor of Ms. Fitness magazine and founder of FitCamps. You also don’t need to spend a lot of money on expensive exercise equipment, Blackburn adds. “Use a thick book to perform triceps presses over your head,” she advises. “A can of peas can be a woman’s upper arm’s best friend because it’s perfect for doing biceps curls.

“A gifted trainer can be a good thing, but you don’t absolutely need one,” says Blackburn. “Instead, invest in a good workout video. That becomes your personal trainer, and it costs only $15 or so.”

Exercising with a friend is another option. “The benefit of working out with a friend is the accountability factor,” says Blackburn. “A training buddy can help your program stay on track.”

10. Myth: Exercise increases appetite.

Reality: “This is really just a rationalization not to exercise,” says Lovins. “People think, ‘I’m overweight, so I’d better not exercise because I’ll just eat more.’ ” However, research indicates that exercising up to one hour actually has a blunting effect on appetite, Lovins notes. Also, if you exercise for longer than an hour, there might be some increase in appetite, but only reflective of caloric expenditure. In other words, you’ll take in only enough extra calories for normal body function — not weight gain.

11. Myth: Wearing weights on your arms and legs makes jogging more effective.

Reality: This fallacy is based on the faulty theory that the extra effort caused by the weights increases the benefits of the exercise. “All weights do is slow you down,” says Lovins. They also can cause injury. When people jog with weights around their wrists, they generally hold their arms at a 90-degree angle. That’s an isometric contraction that increases peripheral resistance and increases systolic blood pressure, which can lead to problems with blood pressure response. In addition, wrist and ankle weights transmit quite a bit of torque force to the joints, which can cause joint damage. Weights also can exacerbate arthritis problems, Lovins adds.

12. Myth: Water will make you slow.

Reality: This myth often is spread by athletic coaches who believe that drinking water during a workout causes athletes to become sluggish, but many gym rats believe it, too. The problem is that it’s untrue — and potentially dangerous, especially in warm climates. “All heat illnesses, such as heat stroke, begin with dehydration,” warns Lovins. “It’s very important to drink plenty of water before, during, and after exercise.”