1. "No pain, no gain" or "Pain is weakness leaving the body."
The first phrase is from the dawn of the modern fitness era (thank you, Jane Fonda). The second is from the U.S. Marines Corps. Unless you want to take a bad trip down memory lane (watch the 1985 movie Perfect to see what gyms used to be like), or commit to the armed forces, both should be completely ignored. Effective exercise should NOT cause pain. Pain is a warning signal from the body to the brain that something is not right. Exercise is physical stress applied to the body, so for changes to occur, some discomfort is to be expected. But discomfort is completely different than pain. Discomfort means you're pushing your body to do the right amount of work, but pain means STOP IMMEDIATELY!
2. Your knees should not go past your toes.
If you have good ankle or hip mobility, then your knees will definitely be able to move past your toes as you sink into a squat. A squatting or bending movement should start from the hips, not the knees. This cue comes from the group fitness world where an instructor trying to provide a safe workout for a large group of people, but it is not a workout rule. If you have the requisite flexibility in your hips and ankles, then you can safely ignore this advice. Here is some great advice on how to progress your workouts so you can squat safely.
3. Train only one body part at a time.
This antiquated thought process comes from the bodybuilder era. The body is designed to move with all muscles and joints working together simultaneously. If you're not planning on walking around a stage in a bathing suit, then your workout program should focus on training your entire body at the same time. Exercises that include the primary movements of squatting (or bending), lunging, pushing, pulling and rotating are all that is necessary for a total-body workout. Doing a movement-based exercise program also uses more muscles than training individual body parts, which means you’ll burn more calories during your workout.
4. Doing crunches.
Want to know a little secret? If you want a six-pack, nutrition plays a much greater role than doing a few sets of crunches. As #3 above points out, all muscles are interconnected via fascia and elastic connective tissue, so doing an exercise to isolate one band of muscle is not an effective use of your workout time. For optimal performance, the muscles of your core should be challenged to move in all directions while you're standing, not simply shortening while you're lying flat on the floor. Here are a number of options to help you develop core strength that don’t require crunches.
5. Weight loss requires only "cardio" exercise.
Are you breathing right now? Congratulations, you're technically doing cardio. Cardio-respiratory simply means using oxygen to help create energy for muscles to burn. All exercise requires muscles to use oxygen, along with either carbohydrates or fats for activity. Think of excess weight as stored energy to burn during exercise. It’s important to note that doing too much aerobic exercise can actually cause the body to burn muscle protein instead of fat, which is not a good thing. In addition to burning calories doing a full-body circuit, weight training helps the body to produce more lean muscle, which means you’ll be burning more energy even when you’re not exercising. Kinda cool, huh?
6. Use light weights and high reps for “toning.”
This is statement is (almost) complete nonsense. The word “tone” comes from the technical term “tonus,” which refers to a state of semi contraction of a muscle. If the goal of weightlifting is to develop muscular definition, the weights should stimulate type II muscle fibers. Using light weights to “tone up” requires doing repetitions until you can no longer move the weight—this is known as volitional fatigue and will ensure that type II fibers have been used. The best way to stimulate type II fibers is to use a heavier weight that will cause fatigue in a shorter period of time. If time is an issue, which would you rather do? Use 5-pound weights for 25 reps or 12-pounds for 8 reps?
There you have it, a list of some fitness advice that you can simply ignore. If you've let life happen to you, have not made fitness a priority and have added a few pounds, keep in mind that they didn't appear overnight and won't disappear immediately. The two keys for a successful exercise program are finding out what works for you and consistency. Finding the right exercise program for your interests will take a little time. Using an ACE-certified Personal Trainer or taking classes with an ACE-certified Group Fitness Instructor are both effective ways to receive the instruction you need to reach your goals.