this image is not available
Media Platforms Design Team

What you don't know about fitness can hurt you—and interfere with your fitness goals. For a safer workout with awesome results, forget everything you think you know about exercise, and read on to get your fitness facts straight.

Check out the Holy Grail of Workouts! Brought to you by Men’s and Women’s Health.

Additional reporting by K. Aleisha Fetters, Dimity McDowell, Robin Hilmantel, Caitlin Carlson, Jenna Birch, Jessica Girdwain, Adam Campbell, and the editors of Women's Health.

MYTH: You can target your fat burn.

this image is not available
Media Platforms Design Team

FACT: Working out can reduce your overall body fat, but you can't control where that fat comes from. In a new study published in Journal of Strength & Conditioning, 11 people completed a 12-week exercise program to train a single leg. Even though they only trained on one side, they lost about the same amount of body fat in each leg—and burned even more body fat above the waist.

Torch fat with this 20-minute fat-burning workout.

MYTH: You shouldn't work out on an empty stomach.

this image is not available
Media Platforms Design Team

FACT: Your body burns more fat when you hit the gym before you eat breakfast, according to a new study published online in the British Journal of Nutrition. Just don't skimp on water.

Refuel with the best post-workout snacks.

MYTH: No pain, no gain.

this image is not available
Media Platforms Design Team

FACT: A little discomfort is okay, but if you feel a sharp pain anywhere, stop what you're doing and consult a doc, says exercise physiologist Dayna Davidson.

Find out where you SHOULD feel the burn.

MYTH: You should stretch before you work out.

this image is not available
Media Platforms Design Team

FACT: Stretching loosens your tendons, and makes muscles feel weaker and less steady, according to a new study. So a pre-workout stretch can actually mess with your workout.

Instead of stretching, try THIS warm up.

MYTH: Lifting heavy weights bulks you up.

this image is not available
Media Platforms Design Team

FACT: Actually, it can slim you down. Women who lift a challenging weight for eight reps burn nearly twice as many calories as women who do 15 reps with lighter dumbbells, according to a study published in Medicine & Science in Sports & Exercise.

New to the weight room? Begin with this weight-room cheat sheet.

MYTH: Exercise machines beat free weights.

this image is not available
Media Platforms Design Team

FACT: Many exercise machines are actually designed for men, which can make it tough for women to nail proper form when you use them. And because machines isolate specific muscles, you actually burn fewer calories on a machine than you do when you exercise freestyle.

Avoid these machines the next time you hit the gym, and try these effective body weight exercises instead.

MYTH: Running on a treadmill is as effective as running outside.

this image is not available
Media Platforms Design Team

FACT: Because running against wind or on uneven terrain engages more of your muscles, it requires more energy and ends up burning about 10 percent more calories than running the same distance on a treadmill.

Try this treadmill workout to torch calories when you can't get outdoors.

MYTH: You shouldn't work out every day.

this image is not available
Media Platforms Design Team

FACT: Rest should be part of your workout, not an alternative to your workout, says Barbara Bushman, Ph.D., a professor of kinesiology at Missouri State University.

Learn 5 ways to make rest part of your workout.

MYTH: You can't work out when you're sick.

this image is not available
Media Platforms Design Team

FACT: As long as you don't have a fever and your symptoms are above the neck (think: stuffy nose or sore throat, not chest congestion or indigestion), you can totally hit the gym. Just listen to your body—or ask your doc if you're unsure.

Getting sick? Try a workout that boosts your immunity.

MYTH: Sweating means you're out of shape.

this image is not available
Media Platforms Design Team

FACT: "It sounds counterintuitive, but the fitter you are, the sooner your body begins to sweat, so a person who's in extremely good shape will produce more sweat than somebody who isn't," says Beth Stover, M.S., C.S.C.S., a senior scientist at the Gatorade Sports Science Institute in Barrington, Illinois. "With each workout, you become a more and more efficient sweating machine."

Debunk even more myths about sweating, here.

MYTH: Crunches are the best moves for your core.

this image is not available
Media Platforms Design Team

FACT: To really cinch your waistline, you're better off doing multi-muscle exercises that target every region of your core. (Crunches don't count.)

Try these 10 exercise moves better than crunches.

MYTH: Working out makes you hungry.

this image is not available
Media Platforms Design Team

FACT: High-intensity exercise may actually decrease food cravings, according to new research published in the International Journal of Obesity.

Curb your appetite with this super-tough workout.

MYTH: Running beats walking.

this image is not available
Media Platforms Design Team

FACT: Since walking and running target the same muscle groups—just at different intensities—they come with similar health results when you compare overall energy burn, according to the author of a recent study. (That said, it takes about twice the amount of time to expend the same amount of energy walking as you would running. So running still wins if you're strapped for time.)

Find out how to walk your butt off.