Some fitness myths have persisted for years, yet adhering to certain misconceptions can be harmful to your health and impede any progress that you might otherwise have made.

Myth #1: Crunches and other abdominal muscles workouts will get you a flat stomach.

Crunches, sit-ups, abdominal rollers and the like are great for toning your stomach, right? Yes and no. Your abdominal muscles are covered with body fat, and the only way to get the six pack you want is to get rid of the fat first. Since you can't target areas on your body for fat removal, replacing abdominal workouts with cardio exercises and weight lifting training will help you burn fat, not only in your stomach, but other areas of the body as well. Cardio by itself will burn belly fat, but at a much slower rate than combining it with weight training.

Myth #2: Drinking lots of water helps you lose weight.

This myth is true, but with a caution. One study by Dr. Brenda Davy, associate professor of human nutrition, foods and exercise at Virginia Tech, found that people who drank two to three glasses of water 20 to 30 minutes prior to each meal lost more weight more quickly than those who didn't. Even drinking one glass of water before a meal caused people to eat 75 fewer calories. If you eliminated 75 calories from each meal (breakfast, lunch, and dinner), you would lose close to one kilogram in a month.

Although it's very rare, it is possible to drink too much water, resulting in hyponatremia, also known as water intoxication. Hyponatremia literally means "low salt," and when the sodium level in blood becomes too low, extra water enters the cells and causes them to swell. This can become potentially harmful or even fatal if the cells in your brain begin to swell, since the skull keeps it from expanding. Luckily, hyponatremia is very rare. If you're unsure about how much you need to drink to lose weight effectively, you can count your body weight in kilograms the number of ounces of water you should drink in a day.

Myth #3: Stretching before a workout prevents injury.

Stretching before a workout doesn't actually increase your range of motion, as many people believe. The Centers for Disease Control and Prevention found that people who stretched before a workout weren't any less prone to injuries than those who didn't. And a 2010 study published in the Clinical Journal of Sport Medicine found that people who used traditional stretching methods, such as touching their toes, were less flexible than those who did more active stretching and used more muscle groups.

Myth #4: Using weight lifting makes you bulky.

Women tend to be especially apprehensive about using weights for fear they'll end up looking like bodybuilders, but they don't have to worry. Muscle takes up less space than fat, so using weights will actually cause your measurements to shrink instead of increase. Strength training helps you lose weight faster and keep it off longer, according to Jeffrey Janot, PhD, an assistant professor of exercise physiology at South Dakota State University.

Also keep in mind that testosterone plays a huge role in increasing muscle size. Since men have 20 to 30 times more testosterone than women, it's more noticeable when they bulk up.

Myth #5: Working out means you can eat whatever you want.

Unfortunately, this myth is just wishful thinking. You still need to count calories in order to lose weight and keep it off, even if you exercise on a regular basis. If you're not sure how many calories you're taking in and how many you're burning, try using a calorie counter program to keep track.