Some of the worst advice out there is if a person is not in pain, then there is no benefit to the exercise being performed. "It's normal to expect some muscle soreness when first beginning an exercise program or doing exercise above their normal frequency, intensity, or duration but there are times when pain is the body's signal to stop exercise and pay attention to an issue than could be made worse if the exercise is continued," says fitness specialist Blenda Cooper over email.

You may have heard it's best to workout in the morning on an empty stomach because you'll burn more calories, but not eating can cause your blood sugar to plummet during a workout, which can leave you lightheaded and dizzy or even make you faint. "This is based on the fact that the blood sugar remains at a low constant during sleep to maintain body function, but fueling needs to happen to impose greater demands on the body after waking up," says Cooper. "Still there are people who wake up and workout without eating anything and this diminishes the body's ability to rebuild and recover."

Injuries should not be taken lightly. "'Just walk it off' implies that by continuing exercise after sustaining an injury, the injured area will get better," says Cooper. "There are times when pain is the body's signal to stop exercise and pay attention to an issue than could be made worse if the exercise is continued."

You may have heard that if your goal is to build muscle, you should avoid doing cardio, as it will "eat" your muscle. Turns out, the opposite is true. "Performing cardiovascular exercise can lead to improving performance, body composition, and improving recovery time away from delayed onset muscle soreness," says certified trainer James Shapiro over email. "Performing excessive cardiovascular activities over a period of time can lead to lower lean body mass as a result of the oxidative energy system being the dominant system of energy exerted."

There is a common myth that the number of reps performed in a set dictates what happens to the body. The bad advice goes something like this:

If you want to add size, do 4-8 reps.

If you want to improve strength, do 8-12 reps.

If you want to improve muscular endurance, do 15-20 reps.

"This common advice has stuck with many for years in their workouts and entrapped exercisers into believing that certain rep ranges yield specific changes," says fitness expert and trainer Mike Clancy over email. "Science has shown this is not the case at all. What actually yields the specific adaptations are a combination of who you are (sex), age, food intake relative to activity, frequency of activity, intensity of sets of activity, number of sets of activity, and many other components."

Daily movement is great, but you shouldn't be doing high-intensity workouts seven days a week. "Our bodies will not make improvements if we work out hard every single day, because they will have no time to recover or repair," says trainer Ashley Pitt over email. "Our muscles build up after they've been broken down in a workout session, and if they don't have a window of at least a day two recover, it will results in less results. In addition, if you work out hard every single day, you will be constantly spiking your cortisol levels. This can lead to more stress and hormone struggles."

Most of us have been to told to stretch before a workout in order to avoid straining a muscle. "However, here is a strong body of scientific evidence showing that not only does static not prevent injuries, it can impair your performance," says sports and exercise scientist Eamonn Leaver over email. "You’ll be able to do less during your workout, especially strength-type exercises and you can actually increase the likelihood of injuring yourself." Instead of doing static stretches as a warm up, do dynamic stretching or a warm up of some light cardio.

"Another piece of horrible fitness advice that i hear is that squatting is bad for your knees," sats Shapiro. "Wrong again. Improper form can lead to having your knees, hips, or back hurt during a squatting. Most people have muscular imbalances and that also tends to lean people to perform the movement improperly. However, the squat is the most personalized movement out there because of the level of mobility the ankle and hip have,the length of your femur, and the strength of your core and back." If you're worried about hurting yourself when squatting, Shapiro recommends talking to a professional about what kind of squat pattern is best for your body and movement pattern.

If you're avoiding weight lifting for fear of looking like the hulk, think again. "Strength training is super important for women, especially as they age," says Lindsay Stiegler, San Francisco Regional Head Coach for Orangetheory Fitness over email. "Women do not have the same amount of testosterone as men and therefore will never gain muscle mass the way men do. The benefits of strength training reach far beyond aesthetics."

Many people think sit-ups and crunches will give them a six-pack, but sadly, it's not that easy. "If there’s a layer of fat on top of the deeper rectus abdominis muscles, it’s not going to show through the adipose tissue that sits atop them," says Dan Gaz, wellness exercise specialist at The Mayo Clinic Healthy Living Program over email. "Overall body fat reduction comes from whole-body caloric expenditure (exercise), rather than doing focused exercises on one spot."