Fitness Myths


Fitness myths are common beliefs about fitness and physical activity that are either false, only partially true, or subject to misinterpretation. Although some fitness myths are harmless half-truths, others may be counterproductive or put people at risk for injury or other negative effects.


Fitness myths abound. Some are longstanding beliefs that survive even as new research proves them false. Other myths are promoted by the fitness industry to market products. Many fitness myths are perpetuated by the media or by experts or professionals with financial ties to fitness companies. Fitness is a very active area of research, and new information may not be widely available, or people may be unwilling to change their habits in light of new findings. The quality of fitness research also varies, and some research funded by the fitness industry may be biased. Finally, individual bodies may respond differently to various procedures, so a product or technique that appears to work for some individuals may not be applicable for others.

General fitness myths

MYTH: FITNESS IS TIME-CONSUMING. Fact: Fitness is not necessarily time-consuming. The American College of Sports Medicine and the Centers for Disease Control and Prevention (CDC) recommend that adults get two strength-training workouts per week—each consisting of about ten repetitions of ten exercises for strengthening each major muscle group, plus one of the following per week:

Thus, fitness requires only 1.25–2.5 hours of aerobic activity per week in addition to two sessions of resistance training. Furthermore, three 10-minute bouts of aerobic exercise are at least as beneficial as one 30-minute workout. Children and teens should get at least an hour of physical activity daily, but this includes recess and other play. Walking for exercise can be combined with various other activities such as birdwatching, museum visits, window shopping, or exercising the dog. Housework, yardwork, gardening, or taking the stairs instead of the elevator may also qualify as aerobic activity. It is important to vary the type of workout, because the body quickly adapts to a single exercise routine, which reduces fitness benefits and increases the risk of injury.

Not only does fitness not have to be time-consuming, but overtraining can be counterproductive: it can increase the risk of injury or lead to consuming excess calories. Excessive aerobic training can lead to a breakdown of muscle tissue and even to a dangerous condition known as rhabdomyolysis. Furthermore, many experts believe that rest days are important for promoting recovery and preventing overtraining injuries.

A related common myth is that sweating is a sign of intense exercise and burning calories or fat. Fact: Sweat has nothing to do with intensity or with calorie burning. Sweating is a mechanism for cooling the skin and regulating body temperature through evaporation. Sweating during exercise is as likely to be a sign of hot weather, an overheated room, or individual physiology as a sign of workout intensity. Furthermore, the fitter people are, the faster they sweat, and very fit people produce more sweat.

MYTH: FITNESS MEANS LOSS OF FAT. Fact: Fitness training increases calorie burning and may modestly increase basal metabolism, but fat loss requires burning more calories than are taken in. The so-called fatburning zone, a target heart rate of 68%–79% of maximum, is a somewhat misleading concept used by the exercise-machine industry and based on the idea that lower-intensity exercise may burn more calories from fat than from carbohydrates (“carbs”). Evidence suggests, however, that high-intensity 10–20-minute interval training is best for fat loss, because more total calories are burned per minute, including a significant number of calories from fat, and metabolism stays higher for longer after exercise. Furthermore, fitness is a measure of cardiorespiratory efficiency, cardiovascular health, and muscle strength, not body weight. Overweight and even obese people can be fit.


Stretching myths

Myth: Stretching decreases the risk of injury. Fact: Static stretching during a warm-up does not decrease the risk of common overuse injuries. Stretching before a workout loosens tendons and makes muscles feel weaker and less steady. Elongating muscle fibers with static stretches can cause a neuromuscular inhibitory response that tightens the muscles to protect them from overstretching; this may decrease strength. In contrast, stretching warm muscles increases blood flow, releases hormones, and allows muscle size to increase slowly and gently. Therefore, warm-ups should be dynamic, involving a range of body movements that promote muscle activation, joint mobility, and range of motion. An active warmup should also increase circulation and body temperature. Brisk walking, light jogging, or jumping jacks are good warmups. Light weights for each body part are good strength-training warm-ups.

Myth: Stretching helps the body recover faster. Fact: Stretching after a workout, when the body is warm, increases joint flexibility but does not appear to reduce muscle fatigue or soreness or speed muscle repair.

Running myths

Myth: Running is bad for the knees. Fact: Studies have found no differences between the knees of older runners and nonrunners, although women runners are at greater risk than men for serious knee injuries. Twice-weekly strength training can build muscle for supporting the knees and reducing the risk of injury.

Myth: Running on a treadmill is better because it puts less stress on the knees than running on asphalt or pavement. Fact: The force on the knee joints comes from body weight, so it is the same regardless of the surface. Running against the wind or on a grade works additional muscles, requires more energy, and burns about 10% more calories than the same distance on a treadmill.

Myth: Barefoot running is better. Fact: Although barefoot running can be beneficial for the body, this depends on one's susceptibility to certain types of injuries. Learning to run barefoot can require prolonged, concentrated effort. People who grow up barefoot land near the front of their feet, but most people who wear shoes land on their heels, which amplifies the force when running. Landing on the forefoot also sends shockwaves up the leg but in a different pattern than heel strikes, so there are risks for different types of injuries from barefoot running.

Strength-training myths

Myth: Cardiovascular exercise (cardio) is better than strength training for fitness and weight loss. Fact: Strength training boosts metabolism, and increasing lean muscle mass can increase basal metabolism. Although cardio is important for fitness, excessive cardio can burn up muscle, which lowers metabolism.

Myth: Weight should be lost with cardio before starting strength training. Fact: Cardio-first causes loss of muscle mass.

Myth: For weight loss, cardio should precede strength training during a workout. Fact: Muscle is required to burn fat, and cardio-first may cause too much fatigue to enable heavy resistance training.

Myth: Lifting weights causes women to bulk up and look like men. Fact: Women do not have enough testosterone to build significant amounts of muscle mass; therefore, strength training by women tends to accentuate the female shape. Most men over 30 or 40 also lack sufficient natural testosterone to build extreme muscle mass. Nevertheless, older men and women can continue to build muscle with a bit more work.

Myth: Strength training requires expensive machines or heavy weights. Fact: Machines can reduce workout intensity, because they isolate specific muscles and fewer calories are burned than with freestyle exercise. Furthermore, many machines are designed for men and are difficult for women to use correctly. Machines are useful for people with limitations due to injury or inexperience, but free weights provide a better range of motion and are better at improving function for daily activities. An individual's own body weight, kettlebells, medicine balls, and resistance bands are all good strength-training tools.

Myth: Muscle definition comes from many repetitions using light weights. Fact: Leanness and muscle definition come from muscle mass and low body fat. Light weights alone cannot build muscle. One study found that women lifting challenging weights for 8 repetitions burned almost twice as many calories as 15 repetitions with lighter weights.

Other common strength-training myths include:

Basal metabolism—
Energy used while at rest to maintain respiration, circulation, and cellular activity.
Body mass index (BMI)—
A measure of body fat; the ratio of weight in kilograms to the square of height in meters.
A unit of energy supplied by food.
Carbohydrate (carbs)—
Sugars, starches, celluloses, and gums that are a major source of calories from foods and supply the body with energy.
Cardiovascular (cardio)—
Activities that temporarily increase heart rate.
Core training—
Exercises that strengthen the trunk and abdominal muscles that stabilize and move the spine.
Animal starch; the form in which glucose is stored in the liver and muscle.
A medicinally inactive substance or procedure.
Chains of amino acids that are essential constituents of all living cells; dietary protein provides energy and essential amino acids.
A rapid breakdown of skeletal muscle that releases muscle cell contents into the blood.
Strength training—
Resistance training; exercise, often with weights, to build muscle strength and mass and anaerobic endurance.
The primary male sex hormone that helps build muscle; men have many times more testosterone than women.
Core-training myths

Myth: Core training is essential. Fact: Many experts believe that core training is overemphasized. Most people achieve core strength through sports and routines such as squats, weightlifting, and even running. Furthermore, depending on the sport, core training may be of no benefit for athletes.

Myth: Crunches flatten the stomach. Fact: Spottraining exercise to reduce fat in particular parts of the body is not possible. Fat is distributed throughout the body, and fitness reduces fat bodywide. Although certain exercises can tone the abdominal muscles (abs), this will not be apparent until excess fat is gone. Crunches tone a small portion of the core but are not the most effective exercise for strengthening the midsection. Core exercises involving the entire trunk including the shoulders and buttocks, such as planks and bridges, are more effective than crunches for fitness. Furthermore, the abdominal muscles work most effectively when standing upright. To be at all effective and to avoid injuring the spine, crunches must be performed correctly and should target all four abdominal muscles. Many experts believe that crunches are unnecessary.

Myth: Squats are bad for the knees. Fact: Full, deep squats are good for the knees. The tops of the thighs should be at least parallel to the floor, preferably lower, even all the way to the toes, while keeping weight on the heels. Never squatting with the knees past the toes is also a myth.

Weight-loss myths

Myth: Heavy people are overweight. Fact: Muscle is denser than body fat, so small muscular people may weigh more than large people with more fat.

Myth: Fit people gain weight because muscle weighs more than fat. Fact: A pound of muscle weighs the same as a pound of fat; however, it is normal to gain weight when first starting weight training, because muscle contains a large amount of water. Weight training is also a source of inflammation, which causes water retention.

Myth: Muscle turns to fat without ongoing exercise. Fact: Muscle does not turn into fat, but some fitness benefits are lost during workout breaks. Furthermore, muscle mass may decrease while appetite remains the same, causing fat accumulation from too many calories and a slower metabolic rate due to lost muscle. Because muscle burns more energy than fat tissue, the higher the fitness level, the faster the rate of calorie burn.

Nutrition myths

Myth: Water and electrolytes prevent cramps. Fact: Dehydration and loss of sodium and potassium have little to do with muscle cramping. Stretching is the best way to relieve acute cramping. Furthermore, overhydration is more of a risk during exercise than dehydration; most people do not need electrolytes following a workout.

Myth: Workouts should be preceded by carbohydrate loading (meals high in carbs). Fact: Carb-loading may have some benefit for endurance athletes, but more balanced nutrition is preferable for most people, who have plenty of glycogen in muscle and the liver for fuel. Carb-loading can induce fatigue and lead to fat storage.

Myth: Supplements are important for fitness. Fact: Supplements are usually unnecessary. Antioxidants such as vitamins A, C, and E destroy free radicals, but some free radicals may trigger reactions that strengthen muscle and improve health. The flavonoid quercetin may be useful for people who are just starting to exercise. Creatine and DHEA (which raises testosterone levels) may be useful for certain athletes.


Role in human health

Fitness is extremely important for physical, psychological, and mental health and for preventing chronic disease. However, adhering to fitness myths may not only interfere with fitness goals, it can be counterproductive and contribute to illness or injury.



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Academy of Nutrition and Dietetics, 120 South Riverside Plz., Ste. 2190, Chicago, IL, 60606-6995, (312) 899-0040, (800) 877-1600, .

American College of Sports Medicine (ACSM), 401 W. Michigan St., Indianapolis, IN, 46202-3233, (317) 6379200, Fax: (317) 634-7817, .

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National Heart, Lung, and Blood Institute, NHLBI Health Information Center, PO Box 30105, Bethesda, MD, 20824-0105, (301) 592-8573,, .

Margaret Alic, PhD

  This information is not a tool for self-diagnosis or a substitute for professional care.