That said, regular activity is an important part of any healthy lifestyle.
Myth: Sit-ups are the quickest ticket to a six-pack.
Truth: As opposed to sit-ups, which target only your abdominal muscles, planks recruit several groups of muscles along your sides, front, and back. If you want a strong core — especially the kind that would give you six-pack-like definition — you need to challenge all of these muscles.
"Sit-ups or crunches strengthen just a few muscle groups," the authors of the Harvard Healthbeat newsletter said. "Through dynamic patterns of movement, a good core workout helps strengthen the entire set of core muscles you use every day."
Myth: Weight training is for men.
Truth: Weight training is a great way to strengthen muscles and has nothing to do with gender.
That said, women produce less testosterone on average than men do, and studies suggest that hormone plays a role in determining how we build muscle.
Myth: It takes at least a couple of weeks to get "out of shape."
Truth: For most people, muscle tissue can start to break down within a week without regular exercise.
"If you stop training, you actually do get noticeable deconditioning, or the beginnings of deconditioning, with as little as seven days of complete rest," said Shawn Arent, the director of the Center for Health and Human Performance at Rutgers University. "It very much is an issue of use it or lose it."
Myth: Running a marathon is the ideal way to get fit.
Truth: You can get many of the benefits of long-distance running without ever passing the five-mile mark.
Not ready to conquer a marathon? No problem. Running fast and hard for just five to 10 minutes a day can provide some of the same health outcomes as running for hours. In fact, people who run for less than an hour a week — as long as they get in those few minutes each day — see similar heart-health benefits compared with those who run more than three hours a week.