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.
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. (Then, check out fitness guide to find out the Best Workout for Your Body Type.)
1. MYTH: You can target your fat burn.1 of 14
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.
2. MYTH: You shouldn't work out on an empty stomach.2 of 14
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.
3. MYTH: No pain, no gain.3 of 14
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.
4. MYTH: You should stretch before you work out.4 of 14
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.
5. MYTH: Lifting heavy weights bulks you up.5 of 14
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.
6. MYTH: Exercise machines beat free weights.6 of 14
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.
7. MYTH: Running on a treadmill is as effective as running outside.7 of 14
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.
8. MYTH: You shouldn't work out every day.8 of 14
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.
9. MYTH: You can't work out when you're sick.9 of 14
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.
10. MYTH: Sweating means you're out of shape.10 of 14
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."
11. MYTH: Crunches are the best moves for your core.11 of 14
Fact: To really cinch your waistline, you're better off doing multi-muscle exercises that target every region of your core.
12. MYTH: Working out makes you hungry.12 of 14
Fact: High-intensity exercise may actually decrease food cravings, according to new research published in the International Journal of Obesity.
13. MYTH: Running beats walking.13 of 14
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.)