The past decade or so has seen an explosion of research about nutrition, exercise and the human body. Some of this research has confirmed what we already knew—things like, a healthy diet and regular exercise make you live long and prosper. Some research, however, has proven that some “common wisdom” about exercise is just plain wrong. Here are ten myths that you don’t want to buy into.

1. Lifting weights makes you bulk up. Actually, this is true—if you are male. Women don’t have the biochemistry necessary to develop big, bulky muscles. They will get stronger, but not bulkier.

2. It’s inevitable to gain weight as you age. False. People gain weight as they age because they become more sedentary and their metabolic rate drops. Weight gain is not inevitable.

3. Fat people are not fit, so you have to lose weight before you can get in shape. False again. Fitness has to do with flexibility, muscle strength and endurance and cardiovascular endurance, not with how fat you are. Fat people may not look fit, but some are in pretty good shape. Getting in shape will also help you lose weight faster because it makes your body burn calories faster.

4. No pain, no gain. Absolutely not. You should not hurt before, during or after exercise. Some mild, transient muscle soreness may occur the first few times you work out, but it should not persist.

5. If you don’t exercise regularly, there’s no point in exercising at all. Nope, not true. Of course, it’s ideal to exercise regularly, but anything at all is better than nothing at all.

6. Old people can’t exercise. Exercise has definite benefits for older people. If you have health problems or haven’t exercised in a while, though, you should check with your doctor and discuss what kind of exercise will be most beneficial for you. There may be some kinds of exercise you should avoid.

7. You can get a flat tummy (or butt or firm thighs, etc) by working those muscles. This one is true—sort of. If you are lean and trim, you can improve the appearance of your tummy or tush with resistance training. If, however, you have a thick layer of fat over your abs and gluts, your tummy won’t get flat. It will, however, get strong, and that will help your posture and prevent back injuries.

8. Always stretch before exercising. Recent research indicates that stretching before a workout doesn’t do any good, and may even limit your performance slightly.

9. Everybody benefits from exercise. True, in some ways. Everybody does get some benefit from exercise. But not everybody gets the same benefit. People have a range of different responses to exercise; Mr. Universe may be able to build big, sculpted muscles while Mr. Milquetoast may never be able to lift more than 50 pounds and just gets “wiry.”

10. You can’t exercise if….. Just about everybody can do some kind of exercise. They do passive exercises on people who are unconscious and on breathing machines in the hospital, for pete’s sake. Many people have exercise limitations, but everybody benefits from moving about a little bit.