Physical fitness is the ability to perform vigorous physical activity. It isnot measured in terms of achieving specific motor skills, but rather it is assessed in terms of muscle strength, endurance, and flexibility. The circulatory and respiratory systems are also involved because of their role in supplying muscles with blood and oxygen.
In considering muscles, strength is the maximum force that can be exerted bya muscle, and endurance is the ability to perform a muscular activity at lessthan maximum force, for example, in doing a series of chin-ups. Flexibilityis the ability of a joint to move through a normal range of motion. The components of physical fitness (strength, endurance, flexibility, and capacity ofcirculatory and respiratory systems) can only be maintained through regular exercise.
Although the percentage of body fat is not a main factor in physical fitness,it must be considered because of its effect on a person's ability to exercise. There is debate in the fitness community about whether an individual can be considered fit if he or she is overweight.
The body will adapt to a regular exercise program by improving the function of the cardiac and respiratory systems. The blood will have a greater capacityto carry oxygen, which in turn will improve the body's ability to work. Theheart and respiratory systems will be more efficient during rest and exercise, and the resting heart rate is usually reduced. These changes take place when a person participates in a rhythmic endurance activity such as walking, running, and cycling, or continuous sports activities such as basketball or tennis.
In addition, an individual participating in a regular exercise program will notice the effects on the skeletal, muscular, and nervous systems. The body will show improved flexibility of the joints along with greater muscle strengthand muscle endurance.
A regular exercise program also benefits the back. At least half of Americansare affected by low back pain, and about 80 percent of these problems are related to muscular problems rather than to the spine. Frequently back problemsare linked to degenerative processes in which the abdominal muscles become too weak or the hamstring muscles at the back of the thighs become tight and inflexible. A consistent strengthening and conditioning program can alleviatesymptoms of back pain.
The death rate from coronary artery disease in the United States is one of the highest in the world. Contrary to many popular ideas, heart attacks are caused by a degenerative process, not by individual instances of exercise, excitement, or heavy eating. Persons in sedentary occupations have a higher rate of coronary heart disease and related deaths than people who are more physically active. Regular physical activity will help reduce the risk of heart attack. If a person who engages in regular exercise does have a heart attack, it is likely to occur late in life and the individual is more likely to survive.Regular exercise helps lower blood triglyceride (fat) levels and cholesterollevels, both of which are related to heart disease.
The effectiveness of exercise depends on the demand on organs and body systems. Individuals participating in the same exercise may not all experience thesame results. Moderation of intensity, duration, and frequency is recommendedto prevent tissue damage.
While isolated attempts at strenuous exercise can cause discomfort, moderateregular exercise contributes to a sense of well-being. Studies of societies in which people commonly live for over 100 years show a common denominator ofmoderate physical activity. Growth and development studies show that active children have stronger muscles and sturdier frames than peers who do not exercise regularly.