By Jessica Smith for Shape.com

Top experts set the record straight on myths that just won't die.

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  • How Much Water To Drink

    <strong>You've heard:</strong> You should drink a gallon of water every day. <br><br> <strong>The truth:</strong>"There is no one right answer to how much water you need, as it depends on each person and their lifestyle -- you may need to modify your fluid intake depending on how active you are, where you live, your health, and if you are pregnant and/or breastfeeding," says Jari Love, a certified personal trainer and creator of the Get RIPPED! Workout. <br><br> While we've all heard the eight glasses a day recommendation, your body may need more or less water than this, especially if you are exercising more often or ingesting more water elsewhere (water-rich foods like fruit and veggies and even beverages like skim milk and juice all count towards your hydration). <br><br> <strong>Bottom line:</strong> "As a general rule of thumb, your fluid intake is probably okay if you are drinking enough each day that you rarely feel thirst and your urine is light yellow or colorless," Love says. "If you have specific concerns or questions about how much fluid you need, check with your doctor." <br><br> <strong>More from Shape.com:</strong><br> <a href="http://www.shape.com/lifestyle/mind-and-body/12-steps-better-sleep" target="_hplink">12 Steps To Better Sleep</a><br> <a href="http://www.shape.com/lifestyle/mind-and-body/6-unconventional-ways-treat-sore-muscles" target="_hplink">6 Unconventional Ways To Treat Sore Muscles</a><br> <a href="http://www.shape.com/lifestyle/mind-and-body/relaxing-101-expert-tips-reduce-stress-and-anxiety" target="_hplink">Expert Tips To Reduce Stress</a> <br><br> <em>Flickr photo by <a href="http://www.flickr.com/photos/mwichary/2820978944/" target="_hplink">Marcin Wichary</a></em>

  • More Sweat = Better Workout

    <strong>You've heard:</strong> Heated workouts are better for you because you burn more calories. <br><br> <strong>The truth:</strong> "This is just an illusion. You burn more calories when you work harder," says Liz Neporent, a health and fitness expert and national spokesperson for the American Council on Exercise. Sweating more might make you think you're working harder, but in order to burn more calories, your muscles have to put out more effort, your heart has to beat faster, and your breathing rate has to increase too, Neporent says. <br><br> What about when the scale says you've dropped a few pounds after a serious sweat session? "You will initially lose more weight when you sweat more," Neporent says, "but as soon as you drink something, you replace the water weight." <br><br> As for claims that the heat will give you a better stretch? That might not be such a good thing, says Amy Dixon, a celebrity trainer and exercise physiologist. "Not only can exercising in the heat be dangerous, it could cause you to get so deep into certain [yoga] poses that you might have to call a friend to help you get out of them!" Yikes! <br><br> <strong>Bottom line:</strong> It's one thing to get hot and sweaty because of the intensity of your workout, but there is no need to seek out extra, external heat sources in order to burn more calories or get a deeper stretch. <br><br> <em>Flickr photo by <a href="http://www.flickr.com/photos/lululemonathletica/4791726982/" target="_hplink">lululemon athletica</a></em>

  • Lift Light Weights To Tone Up

    <strong>You've heard:</strong> To avoid bulking up, you should skip heavy weights and do a lot of reps with light weights. <br><br> <strong>The truth: </strong>This myth just won't seem to go away! Most women don't have the hormones or the muscle mass needed to get really big muscles, Neporent says. "You'd have to spend hours and hours in the gym to build up [muscle mass], and even then most women are incapable of really bulking up." <br><br> Don't shy away from weights that challenge you. To reshape your body, Neporent recommends lifting heavier weights and pushing yourself to the point where you fatigue your muscles within 8-15 reps. <br><br> <strong>Bottom line:</strong> It's a great idea to incorporate heavy weight lifting into your workout routine. Just be sure to gradually work up to more challenging weights and always practice good lifting form and technique. If you're not sure how to perform a certain move, ask a trainer or look to helpful online resources.

  • Sweat Eliminates Toxins

    <strong>You've heard:</strong> Sweating detoxes your body. <br><br> <strong>The truth:</strong> While it is true that a small amount of toxins leave our body through our sweat glands, it's only about one percent of the total amount, Love says. "The main role of sweating is to regulate the temperature of the body; the main organs responsible for excreting waste are actually the gastrointestinal tract -- the liver, kidneys, immune systems and lungs." <br><br> <strong>Bottom line:</strong> Working up a good sweat is beneficial for your body, but do it to feel better and be healthier, not for the purpose of "detoxifying" your system. <br><br> <em>Flickr photo by <a href="http://www.flickr.com/photos/mikebaird/3539161615/" target="_hplink">mikebaird</a></em>

  • The Formula For Flat Abs

    <strong>You've heard:</strong> For flat abs, you should work them every day. <br><br> <strong>The truth:</strong> Like every other muscle group in your body, your abs need time to rest and recover. "Training a muscle causes the muscle to break down, and it is during rest that it is allowed to repair and rebuild itself," says Tom Holland, an exercise physiologist and author of "Beat the Gym". <br><br> While crunches, planks and other abs exercises have their benefits, there is no need to do hundreds of reps or perform them every single day. If you really want to do something positive for your abs every day, focus on your eating habits. "Abs are made in the kitchen, not by crunches," Holland says. <br><br> <strong>Bottom line:</strong> Train your abs like every other muscle group, allowing time for recovery. And be sure to follow a diet that will help you see the results of all your hard work. <br><br> <em>Flickr photo by <a href="http://www.flickr.com/photos/alaina_marie/4377272795/" target="_hplink">alaina.buzas</a></em>

  • Cycling Builds Up Your Thighs

    <strong>You've heard:</strong> Cycling with a lot of resistance makes your thigh muscles (quads) bigger. <br><br> <strong>The truth:</strong> Cycling is a cardiovascular activity, not a strength builder, Dixon says. "In order for an exercise to be considered a strength-building activity, it requires working the muscles to complete fatigue," she says. In other words, you would need to put enough resistance on the bike to completely fatigue your legs in 6-8 revolutions. The right amount of resistance can make the difference between a great workout and just spinning your wheels. <br><br> "Resistance is a good thing," Dixon says. "Put it on and you will burn more calories and relish in the power you can push." <br><br> <strong>Bottom line:</strong> You'll get a better workout and burn more calories -- not build bigger muscles -- by using resistance during your cycling workouts.

  • The Truth About Abs Exercises

    <strong>You've heard:</strong> Crunches (and other abs exercises) are best for melting fat around your middle. <br><br> <strong>The truth:</strong> "You may add tone and strength to your middle by doing crunches and other abs exercises, but you won't melt off fat," Neporent says. You can't spot reduce the abs or any other part of your body. The only way to lose belly fat is by reducing overall body fat -- some will come off your trouble zones, but how you lose fat is genetically determined, Neporent says. <br><br> <strong>Bottom line:</strong> To shed belly fat and burn more calories during your workout, shift your focus from crunches to total-body moves that work multiple muscle groups at once (including your abs). And be sure to supplement your hard work at the gym with a healthy diet. <br><br> <em>Flickr photo by <a href="http://www.flickr.com/photos/dvids/7094321263/" target="_hplink">DVIDSHUB</a></em>

  • Pilates Creates Long, Lean Muscles

    <strong>You've heard:</strong> Pilates and yoga create long, lean muscles. <br><br> <strong>The truth: </strong>While you may feel longer and taller after a great Pilates or yoga session, it's physically impossible to lengthen a muscle. "Muscles have a fixed origin and insertion point, therefore the only way to truly 'lengthen' a muscle would be to surgically detach and reattach it," Holland says. <br><br> So why are almost all Pilates and yoga instructors so tall and slim? They were born that way, Holland says. "Women who possess the Pilates or yoga 'physique' walked in the door that way. They are ectomorphs, born with the long, lean physique." <br><br> <strong>Bottom line:</strong> Pilates and yoga both offer plenty of benefits, including improved flexibility and posture that can help you feel and appear a little taller, they just can't actually make your muscles 'longer.' <br><br> <em>Flickr photo by <a href="http://www.flickr.com/photos/lululemonathletica/3931787319/" target="_hplink">lululemon athletica</a></em>

  • The "Fat-Burning" Zone Is The Best For Weight Loss

    <strong>You've heard:</strong> To burn the most fat, you should do your cardio in the "fat-burning zone." <br><br> <strong>The truth: </strong>"This is fuzzy math," Holland says. While you do burn a higher percentage of calories from fat at lower intensities, you burn more more calories overall by exercising harder. <br><br> Endurance exercise has its place in a balanced training routine, but it shouldn't be the only type of cardio you do. That's why we love Tabata training and HIIT (high intensity interval training) for super-effective and efficient cardio sessions. <br><br> <strong>Bottom line:</strong> To burn the most fat, create a well-rounded workout schedule that mixes strength training, high-intensity cardio, and lower-intensity sessions if you want an extra hit of cardio. And of course, supplement your training with a healthy diet. <br><br> <em>Flickr photo by <a href="http://www.flickr.com/photos/mahidoodi/199747855/" target="_hplink">maHidoodi</a></em>

  • Go Gluten-Free To Slim Down

    <strong>You've heard:</strong> Going gluten-free will help you lose weight and improve your health. <br><br> <strong>The truth:</strong> Gluten-free foods still contain calories and won't automatically boost your health or slim you down. In fact, many experts say gluten-free products might not be worth the higher price. Unless you are truly allergic to gluten and have the autoimmune disorder known as celiac disease (which only applies to one in 133 Americans, according to the Celiac Disease Foundation), going gluten free may not make much of a difference. <br><br> According to Italian researchers, whose editorial piece was published in the February 2012 edition of the <em>Annals of Internal Medicine</em>, there just isn't enough scientific evidence to conclude that a gluten-free diet alleviates symptoms in patients that don't have celiac disease. Instead, they suggest that people who go without gluten may believe they feel better simply because of the hype surrounding this diet (like Miley Cyrus's recent gluten-free endorsement and weight loss). <br><br> You may also start to feel better as a result of adopting an overall healthier lifestyle. "When we get on any sort of health kick or jump on board with a new fad, we also add in exercise, drink more water, watch our sugar, and cut down alcohol," says Rania Batayneh, M.P.H., a nutritionist, eating strategist, and owner of Essential Nutrition for You. "This has nothing to do with being gluten free but just downright healthy!" <br><br> If you go from eating a diet heavy in refined, processed foods (that contain gluten) to eating more fresh, whole foods (that are naturally gluten-free), you are more likely to lose weight and feel better. But if you simply swap out whole-wheat bread for rice bread, there's really no calorie difference, so don't just do it to lose weight, Batayneh says. <br><br> <strong>Bottom line:</strong> A cupcake is still a cupcake, and making it gluten free won't suddenly turn it into a health food. Save your money by skipping gluten-free packaged foods and focus on filling your diet with as many whole, unprocessed foods as possible. <br><br> <strong>More from Shape.com:</strong><br> <a href="http://www.shape.com/lifestyle/mind-and-body/12-steps-better-sleep" target="_hplink">12 Steps To Better Sleep</a><br> <a href="http://www.shape.com/lifestyle/mind-and-body/6-unconventional-ways-treat-sore-muscles" target="_hplink">6 Unconventional Ways To Treat Sore Muscles</a><br> <a href="http://www.shape.com/lifestyle/mind-and-body/relaxing-101-expert-tips-reduce-stress-and-anxiety" target="_hplink">Expert Tips To Reduce Stress</a> <br><br> <em>Flickr photo by <a href="http://www.flickr.com/photos/jronaldlee/4658320554/" target="_hplink">jronaldlee</a></em>

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