It is hard to say where they got started, but many commonly held fitness "truths" are really fiction. For the most part, they won't really hurt you, but some can really ruin the effectiveness of your program. Here are the facts behind some common fitness fictions.

• Strength training turns fat into muscle and when you stop working out, the muscle turns back into fat.
  The reality is that fat and muscle are two entirely different parts of the body and have very different functions. One cannot change one into the other. Fat is stored energy (calories you haven't used yet) and is stored in many places throughout the body – most notably under the skin. Muscles, on the other hand, are what move your body. When you work out, you may increase the amount of muscle tissue in your body and/or decrease the amount of body fat stored, but you aren't converting one to the other. When you stop working out, muscle size decreases and body fat increases, which can give the impression of muscles turning to fat.
   
• Doing abdominal exercises will give you a flat stomach.
  Abdominal exercises are intended to strengthen the abdominal muscles, of which there are several. The "stomach" is an organ and will not be affected by crunches. If you are trying to reduce the amount of body fat stored around the pelvis, you need to do cardiovascular exercise. This is not to say that abdominal exercises are worthless. They are very important. Having a strong core will help prevent many injuries (including back problems) and abdominal exercises are part of a well-rounded program.
   
• Using the adduction/abduction machines (inner/outer thigh) will make your legs thinner.
  This is a similar situation to the abdominal exercises. It is not possible to "spot reduce" meaning choose an area of the body and decide to make it smaller. The only way to reduce body fat is to take in less calories than you use. The ad/abductor exercises (this also includes floor exercises) are designed to increase the muscles that move the body from side-to-side. This doesn't necessarily mean it will make the legs bigger, but they are certainly not going to make them smaller.
   
• Doing strength training everyday will speed up your progress.
  Strength training every day actually will lessen progress and possibly cause injury over time. All physical conditioning is based on the concept of overload and recovery. When you lift weights, you cause microscopic tearing to the muscles. (This is really a good thing!) On the off day, the muscles are able to repair themselves in preparation for the next session. If there is no off day, all you have is day-after-day of tearing, which eventually will lead to an injury. So there is no benefit in doing more than 3-4 days of strength training each week.
   
• Eating protein makes your muscles bigger.
  Although muscles are made up of proteins, the act of eating protein does not generate an increase in size. Only strength training can effect an increase in muscle size. In fact eating too much protein can have some drawbacks. Eating more calories than your body needs will cause you to store body fat. It doesn't matter if it is protein, carbohydrates, or dietary fat; too many calories will increase body fat. Excess protein can also lead to more serious health problems, so it is not a good idea to eat more than your body requires. To increase muscle size, you need to do consistent strength training workouts.
   
• Using free weights will make your muscles big while using machines will tone your muscles.
  The effects of resistance training are a result of intensity, frequency, and genetics, not the type of resistance used. If your program follows the principles of fitness, it doesn't matter if you are lifting rocks. Machines allow a person to perform the exercise with less chance of injury, and are often less intimidating. Free weights, on the other hand, allow for multiple exercises and infinite combinations of exercises, which is beneficial to avoiding a stale program. Free weights also will fit almost anybody's size and shape. A successful strength training program depends more on the consistency and execution of the exercises than on the equipment used.
   
• Exercising in the "fat-burning" zone is the best way to lose weight.
  This is one of the most confusing aspects of fitness. Technically, there is a point where the body uses body fat for energy and the physiological impulse for this happens at a slightly lower heart rate. However, this information is really only relevant to elite level athletes looking for a performance enhancing edge. For people trying to reshape their bodies, the important factor is the total amount of calories used versus the total amount of calories ingested. Let's say two people are exercising for 30 minutes. The first person is exercising at less intensity (the so-called "fat-burning zone") while the second person is exercising at a much higher intensity. This means the first person should have used more body fat, right? Wrong, the truth is, the second person used more calories and at the end of the day ended up with a larger caloric deficit than the first person. If this is repeated every day, it is the second that will lose more body fat. So don't be misled by those "fat-burning" programs at the gym.
• 
  Read more articles: