Aerobic Exercise, Running
Image Caption : Aerobic exercise improves oxygen consumption by the body. Benefits include strengthening the heart's pumping efficiency, improving circulation, lowering blood pressure, and stimulating the production of more red blood cells for oxygen transport. Aerobic exercise conditions the heart and lungs by increasing the oxygen available to the body and by enabling the heart to use oxygen more efficiently. Exercise alone cannot prevent or cure heart disease. It is only one factor in a total program of risk reduction; examples of other factors are high blood pressure, cigarette smoking and high cholesterol level.
Aerobic means "oxygen-producing." Aerobic exercise, sometimes called endurance training, improves oxygen consumption by your body and strengthens your cardiovascular system and endurance. Activities like walking, running, swimming, and biking, in which you remain in motion and your heart rate increases for an extended period of time, are considered aerobic. When your heart is beating more rapidly, more blood is circulated around your body and more oxygen is provided to your tissues and cells.
Your heart is a muscle like any other in your body, and with regular exercise it will become stronger and slightly larger. (This is different from an enlarged, or hypertrophied, heart, in which the heart muscle thickens and actually becomes weaker.) A stronger heart can pump more blood with each beat, so that it takes fewer beats to circulate your blood. Your heart rate drops, and your heart is able to rest more between beats. But if you don't get enough exercise, your heart is weaker, has less muscle tone, and has to work harder to pump the blood. This raises your blood pressure and stresses your whole cardiovascular system.
As you progressively condition your heart with aerobic exercise, not only does your heart become stronger, but your entire body responds. New capillaries grow in your muscles and in the heart muscle itself. In fact, endurance-trained athletes have 40% more capillaries per muscle than untrained people. Your muscle cells themselves change in ways that allow them to extract greater amounts of oxygen and nutrients from the bloodstream and use them to produce energy. Your blood pressure lowers, and your body produces more red blood cells to transport oxygen.
Exercise strengthens bones ligaments and tendons by encouraging the laying down of connective tissue. Your joints become stronger and less prone to injury. Your bones will also lose less calcium as you age, helping to prevent osteoporosis.
Moderate Intensity vs. Short Bursts
It's long been thought that aerobic exercise works best when performed at moderate intensity over a long period of time. But new evidence shows that short, intense bursts of exercise may work just as well for cardiovascular health. In one study, doing about 50 minutes of moderate-intensity cycling 5 days a week provided the same benefits to the arteries as doing short, intense cycling sprints (resting between sprints) for a total of about 20 minutes, just 3 days a week. Consider this type of exercise if time is an issue for you, but consult your doctor first, as intense exercise may increase the risk of injury.
Slow fibers are predominantly used in endurance exercises that require little force but involve numerous repetitions. The aerobic metabolism used by slow-twitch fibers allows them to maintain contractions over long periods. Endurance training modifies these slow fibers to make them even more efficient by producing more mitochondria to enable more aerobic metabolism and more ATP production. Endurance exercise can also increase the amount of myoglobin in a cell, as increased aerobic respiration increases the need for oxygen. Myoglobin is found in the sarcoplasm and acts as an oxygen storage supply for the mitochondria.
The training can trigger the formation of more extensive capillary networks around the fiber, a process called angiogenesis, to supply oxygen and remove metabolic waste. To allow these capillary networks to supply the deep portions of the muscle, muscle mass does not greatly increase in order to maintain a smaller area for the diffusion of nutrients and gases. All of these cellular changes result in the ability to sustain low levels of muscle contractions for greater periods without fatiguing.
The proportion of SO muscle fibers in muscle determines the suitability of that muscle for endurance, and may benefit those participating in endurance activities. Postural muscles have a large number of SO fibers and relatively few FO and FG fibers, to keep the back straight (Figure). Endurance athletes, like marathon-runners also would benefit from a larger proportion of SO fibers, but it is unclear if the most-successful marathoners are those with naturally high numbers of SO fibers, or whether the most successful marathon runners develop high numbers of SO fibers with repetitive training. Endurance training can result in overuse injuries such as stress fractures and joint and tendon inflammation.
Long-distance runners have a large number of SO fibers and relatively few FO and FG fibers. (credit: “Tseo2”/Wikimedia Commons)
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The material on this site is for informational purposes only and is not intended as medical advice. It should not be used to diagnose or treat any medical condition. Consult a licensed medical professional for the diagnosis and treatment of all medical conditions and before starting a new diet or exercise program. If you have a medical emergency, call 911 immediately.