But on The Early Show Wednesday, Shape Magazine Deputy Editor Janet Lee sorted out what's factual, and what isn't.
She also dispensed advice to help you get more calorie-burning, muscle-toning oomph out of every workout session!
MYTH: CRUNCHES WILL GET RID OF YOUR POT BELLY. AND/OR YOU CAN ISOLATE YOUR "LOWER ABS"
TRUTH: Crunches won't get rid of body fat. You have to do cardio to do that. Crunches will firm up the underlying muscles, though. Also, there is no such thing as "lower abs." The six-pack you're going for is actually one long muscle, called the rectus abdominis, that extends from below your chest to your pubic bone. To work your abs, you should do exercises to target all four muscles: the rectus abdominis, internal and external obliques and the transverse abdominis.Getting a six pack is more about genetics first and percentage of body fat second. To try to get there, do a range of moves that target your entire midsection (all 4 muscles in the abs) and do cardio to burn fat.
MYTH: STRETCHING WILL PREVENT INJURY AND ENHANCE YOUR PERFORMANCE
TRUTH: There's no conclusive research showing that stretching before or after your workout will keep you from injuring a hamstring or make you go faster (it could make you go slower!). But it does feel good and it can increase your range of motion so certain activities are easier. Where stretching really makes a difference is during the day, when you're stiff from typing on your computer or lifting boxes or whatever. It's better to stretch periodically throughout the day. Before working out it will help prevent injury and enhance your performance to do a gradual warm-up that includes some cardio and what is sometimes called movement prep, doing light movements that prepare you for the actual motions you'll do during your workout.
MYTH: PILATES CAN LENGTHEN YOUR MUSCLES
TRUTH: Only growing will make your muscles longer. They may LOOK longer because the workout you're doing is a different type of movement and you're moving different and standing taller, but the muscles aren't actually growing longer.Pilates doesn't lengthen muscles--it tones and stretches them, which doesn't mean the muscles get longer. Pilates does an excellent job of improving core strength and postural awareness, which can make you look longer and leaner. If you stand taller and extend your arms farther, you will have the appearance of longer muscles.
MYTH: BUILDING MUSCLE IS THE BEST WAY TO SPEED UP YOUR METABOLISM
TRUTH: If you're looking for a big metabolism boost (hundreds of calories) aim to do higher intensity cardio in addition to weight training for a maximum metabolism lift. Weight training will build muscle which burns more calories than fat, but the average person doesn't add a ton of muscle. You're better off trying to burn as many calories as you can during your workout and getting that temporary metabolism boost. E.g., you can add four pounds of muscle and burn maybe 150 more calories a day OR you can do interval training during your cardio session and burn 500 calories during your workout. Combine them for the max effect.
MYTH: MUSCLE TURNS TO FAT WHEN YOU STOP WORKING OUT
TRUTH: Muscle doesn't turn to fat-ever! Some people that are very muscular and stop working out without changing their diet may put on fat though and their muscles will lose tone after 4 to 8 weeks. If you have a to take a gym break, try to work in activity in other ways (walk more, take the stairs, etc.) and cut back on what you're eating. Muscle and fat are different types of tissue, and one can't morph into the other. What can happen when you stop exercising is that you put on fat, so those once-flat abs will turn distinctly flabbier. Also, when you don't use muscle it starts to atrophy, so it's not as firm as it was.
MYTH: LIFTING WEIGHTS REGULARLY WILL MAKE YOU LOOK BULKY
TRUTH: Most women can't develop muscles like men do. But if you find yourself adding more muscle than want, don't give up on weight training. Instead, reduce the load by working with lighter weights, and do moves that use your own body for resistance. Many of the people you see at the gym who are looking bulky are men or women who are working very hard at building muscle. The average woman doesn't a) produce enough testosterone to build significant bulk and b) doesn't lift heavy enough weights or often enough to build bulk.