Fitness Myth No. 4: Swimming is a great weight loss activity.
While swimming is great for increasing lung capacity, toning muscles, and even helping to burn off excess tension, Harr says the surprising truth is that unless you are swimming for hours a day, it may not help you lose much weight.
"Because the buoyancy of the water is supporting your body, you're not working as hard as it would if, say, you were moving on your own steam -- like you do when you run," says Harr.
Further, he says, it's not uncommon to feel ravenous when you come out of the water.
"It may actually cause you to eat more than you normally would, so it can make it harder to stay with an eating plan," he says.
Fitness Myth No. 5: Yoga can help with all sorts of back pain.
"If your back pain is muscle-related, then yes, the yoga stretches and some of the positions can help. It can also help build a stronger core, which for many people is the answer to lower back pain," says Schlifstein.
But if your back problems are related other problems (such as a ruptured disc) yoga is not likely to help, he says. What's more, it could actually irritate the injury and cause you more pain.
If you do have back pain, get your doctor's OK before starting any type of exercise program.
Fitness Myth No. 6: If you're not working up a sweat, you're not working hard enough.
It's possible to burn a significant number of calories without breaking a sweat: Try taking a walk or doing some light weight training.
Fitness Myth No. 7: As long as you feel OK when you're working out, you're probably not overdoing it.
One of the biggest mistakes people tend to make when starting or returning to an exercise program is doing too much too soon. The reason we do that, says Schlifstein, is because we feel OK while we are working out.