12 fitness 'truths' that are doing more harm than good

• Exercise is the closest thing to a miracle drug that we have, but much of the public wisdom surrounding fitness has been either too vague or conflicting to be helpful.
• Scientists have been studying many of the same questions that you have probably encountered while structuring your workout routine.
• Learn the best time to workout, how often you should be exercising to tone up, and the best pre- and post-workout fuels for your routine.

How many times a week do you need to work out to get in shape? If you're trying to lose weight, should you focus on exercise or diet? Is it better to hit the gym in the morning or at night?

Whether you want to tone up, slim down, or simply boost your mood, you've likely come across these questions, but the answers may have seemed either contradictory or too vague to be helpful. On top of that, dozens of fitness myths plague the wellness world, making it tough to separate fact from fiction.

Fortunately, exercise scientists and physiologists have been researching all of these topics too, and the emerging research from their work can help you dispel the myths and hit the track with confidence.

DON'T MISS: One type of exercise is the closest thing to a miracle drug that we have — and new research suggests intense workouts aren't the only option

SEE ALSO: The best ways to lose weight and keep it off, according to science

Myth: For any real benefits, you need to hit the gym for at least an hour or sweat it out several times a week in a fitness class.

Truth: For better health and a reduced risk of death from all causes, any kind of movement is better than little or none.

That means that any effort that gets you moving and breathing — whether it's a twice-weekly heart-pounding kickboxing class or a 30-minute walk to work — has measurable benefits for your brain and body.

That's according to new researchpublished this month in the Journal of the American Heart Association. To arrive at their findings, researchers used data on physical activity and death rates from national surveys of more than 4,800 adults and found that so long as people moved around for at least 30 minutes per day — whether it was through a combination of brisk walking and stair-climbing or a spin class — they enjoyed significant benefits compared against those who didn't exercise at all.

"The key message based on the results," the authors wrote, "is that total physical activity (i.e., of any bout duration) provides important health benefits."

Myth: It takes at least two weeks to get 'out of shape.'

Truth: In most people, muscle tissue can start to break down within a week without regular exercise.

"If you stop training, you actually do get noticeable de-conditioning, or the beginnings of de-conditioning, with as little as seven days of complete rest," Shawn Arent, director of the Center for Health and Human Performance at Rutgers University, said. "It very much is an issue of use it or lose it."

Myth: Sit-ups are the best way to get 6-pack abs.

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 6-pack-like definition — you need to challenge all of these muscles.

"Sit-ups or crunches strengthen just a few muscle groups," write the authors of the Harvard Healthbeat newsletter. "Through dynamic patterns of movement, a good core workout helps strengthen the entire set of core muscles you use every day."