Physical exercise is activity performed in order to develop or maintain physical fitness and overall health. Frequent and regular exercise is an important component in the prevention of some of the diseases of affluence such as cancer, heart disease, diabetes and obesity.

Exercises are generally grouped into three types depending on the overall effect they have on the human body:

Flexibility exercises such as stretching improve the range of motion of muscles and joints.
Aerobic exercises such as walking and running focus on increasing cardiovascular endurance.
Anaerobic exercises such as weightlifting increase short-term muscle strength. Exercise can be an important part of physical therapy, weight loss or sports performance.

Proper nutrition is as important to health as exercise. When exercising it becomes even more important to have good diet to ensure the body has the correct ratio of macronutrients whilst providing ample micronutrients, this is to aid the body with the recovery process following strenous exercise.

"Exercise bulimia" is a disorder in which too many calories purged from the body through exercising.

It should be noted that Delayed Onset Muscle Soreness can occur after any kind of exercise, particularly if the body is in an unconditioned state relative to that exercise.

Exercise benefits
Frequent and regular exercise has been shown to help prevent or to improve major illnesses such as high blood pressure, obesity, heart disease, diabetes, insomnia, cancer and depression, among others.

Common myths
Many common myths have arisen surrounding exercise, some of which have a basis in reality, and some which are completely false.

Spot reduction.
It is a common belief that training a particular bodypart will preferentially shed the fat on that part; for example, that doing sit-ups is the most direct way to reduce subcutaneous belly fat. This is false. Most of the energy derived from fat gets to the muscle through the bloodstream and reduces stored fat in the entire body. Fat is reduced in a pattern determined mostly by genetics. Sit-ups may improve the size and shape of core muscles and may reduce the unsightly appearance of belly fat, but the belly fat will often be the last fat removed from the body.

Only overweight people need a physical before beginning an exercise program. Absolutely false. Only a physician can determine your ability to engage in an exercise program. Apparently healthy people can still have unknown medical conditions, such as a heart murmur, that can cause severe injury or death not only to themselves, but also to others that are dependent upon them, such as someone they are spotting.

List of activities used as physical exercises
aerobics, calisthenics, cycling, dancing, pilates, rowing, running, sexercises, sport, stretching, walking, warming up, weight training, yoga and dancing

List of classes of physical exercise
Aerobic exercise, Anaerobic exercise, Endurance exercise, High-density exercise, High-intensity interval training and Resistance training. Some activities can fall into more than one class of exercise. For instance: cycling can be used for endurance or high-intensity interval training; weightlifting is resistance training and can be high-density exercise with certain workout designs.

Breathing
Active exhalation during physical exercise helps the body to increase its maximum lung capacity, and oxygen uptake. This results in greater cardiac efficiency, since the heart has to do less work to oxygenate the muscles, and there is also increased muscular efficiency through greater blood flow. Consciously breathing deeply during aerobic exercise helps this development of the heart lung efficiency.

During breathing, males mostly use the intercostal muscles in the rib cage, females mostly use abdominal muscles. In strenuous exercise, it is likely that these differences diminish.

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