Aerobics include any exercises that increase the heart rate and breathing rate for a sustained period of time, greatly increasing the flow of oxygen and blood to all parts of the body. Aerobic exercise, or cardiovascular exercise, provides all these benefits:

• Increased lean muscle
• Decreased intramuscular and subcutaneous fat
• Improved circulation
• Elevated metabolism
• Increased energy and stamina
• More restful sleep
• Reduction of mild depression, anxiety, and muscle tension
• Improved appearance
• More positive self-image and outlook on life
• Reduced use of coffee, tea, alcohol, tobacco, sugar, and refined carbohydrates
• Increased immune function by increasing the white blood cell count
• Increased HDL and decreased LDL.

To be most effective, the exercise must raise your pulse rate to the range indicated in the formula in the next article, and keep it at that level for not less than twenty minutes. (Note: People who are not in good cardiovascular condition should begin at a lower level and can break their exercise time into five-minute periods with rests in between.) Try to exercise three times a week.

Examples of aerobic exercises are bicycling, aerobic dance and step classes, running, swimming, jumping rope, and vigorous walking. Stop-and-go exercises (such as golf, downhill skiing, housework, and gardening) and those of short duration (like sprinting, square dancing, and calisthenics) do not produce the desired cardiovascular benefit.

As soon as you start moving, your heart starts working harder, pumping more blood with each beat. The blood then rushes with greater speed and force through the vessels, which expand to allow for this increased volume. The working muscles call out for more oxygen. The body responds by breathing more deeply. In moving to arms and legs, the blood is diverted from the digestive organs. Blood vessels in the exercising muscles expand tremendously, allowing a greater influx of oxygen. The process returns to its starting point as the blood goes back to the heart, faster and in greater volume, filling it to capacity and keeping the whole operation working smoothly. Stressing the whole system in this way improves its function and increases its capacity to handle more stress.

Circulation is not the only process affected during aerobic exercise. The body's energy supply shifts from glucose to fat usage. Fat stored in body tissues is released, moving first to the liver for breakdown, then out to the needy muscles to fuel them. Hormones and enzymes jump in to keep the system in balance, and the chemistry of the brain itself is altered.

Other Types of Exercise

It is important to understand that the exercise most effective in preventing heart disease is cardiovascular exercise (see next articles), but there are also two other types of exercise, each categorized by the body systems most influenced:

• Cardiovascular exercise (aerobics) stimulates heart and lungs and builds endurance.
• Flexibility exercise lengthens and stretches muscles to enhance balance and overall grace and agility.
• Strength-developing exercise (such as weight training) increases muscle mass, potentially creating a leaner appearance.

For basic fitness, all three are essential. Flexibility and strength-developing exercises will be covered in the next articles.

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