How Does Blood Move Through the Body?

The amount of oxygen required for human exercise increases with exercise intensity. When the human body is exercising, through neuromodulation and body fluid regulation, on the one hand, it expands the blood vessels in the muscles, on the other hand, it strengthens the heart's activity, so that the heart emits more blood in a unit time, so that more blood flows faster. Into the moving muscles, get enough oxygen to the muscles.

Exercise and blood circulation

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The amount of oxygen required for human movement

Blood circulation refers to the continuous flow of blood in the heart and blood vessels throughout the body. The heart is constantly contracting and relaxing, which is the driving force for blood flow, and blood vessels are the channels for blood flow. Blood mainly carries various substances, including various energy substances closely related to sports, as well as oxygen and carbon dioxide.

Oxygen in the air diffuses from the alveoli into the blood, a small part of which can be dissolved in the plasma. This part of oxygen is very small, only about 0.3 milliliters per 100 milliliters of blood, and most of the rest are transported by chemical bonding. of. Hemoglobin in red blood cells has a characteristic that it is easy to combine with oxygen in places where the oxygen partial pressure is high, and it is easy to dissociate from oxygen in places where the oxygen partial pressure is low. It is the best carrier of oxygen. Each gram of hemoglobin can bind 1.34 to 1.36 milliliter of oxygen. Chinese adult men contain about 14.4 grams of hemoglobin per 100 milliliter of blood, and women of about 13.3 grams. Therefore, for every 100 milliliters of blood in the arteries, men can carry 19.3 milliliter of oxygen, and women can carry 17.8 ml of oxygen.

When this oxygen-saturated blood flows to the tissue, because the tissue continuously consumes oxygen, the oxygen partial pressure is lower here, and the oxygen bound by hemoglobin is immediately dissociated for use by the tissue; finally, the tissue returns to the vein. In blood, only 13 ml of oxygen may be left for every 100 ml of blood, that is, 6 ml of oxygen per 100 ml of blood is used by the tissue.

Muscle activity intensifies during exercise, which not only consumes more oxygen and reduces the oxygen partial pressure, but also generates a large amount of carbon dioxide and raises the local temperature. Under this condition, the oxygen bound to hemoglobin is more easily dissociated, so as the blood flows through the active muscles, more oxygen dissociates. From the measurement of arterial and venous oxygen content, it can be known that the oxygen used by muscle tissue can reach 16-17 milliliters at the same time. At the same time, this dissociation process is also accelerated. It takes 0.7 seconds when it is quiet and only needs to be taken during exercise. 0.35 seconds.

The amount of oxygen required for human exercise increases with exercise intensity. When the human body is exercising, through neuromodulation and body fluid regulation, on the one hand, it expands the blood vessels in the muscles, on the other hand, it strengthens the heart's activity, so that the heart emits more blood in a unit time, so that more blood flows faster Into the moving muscles, get enough oxygen to the muscles.

The amount of blood that is ejected into arterial vessels through ventricular contraction is called cardiac output. The amount of blood ejected per beat of the heart is called the stroke output; the amount of blood ejected per minute is called the output per minute. Because the output per minute is equal to the stroke output multiplied by the heartbeat frequency, in order to increase the output per minute during exercise, you must increase the stroke output, or increase the heartbeat frequency, usually both. At rest, the stroke volume is 50 to 70 milliliters, and the heart rate is about 70 beats per minute, so the output volume per minute is generally about 4 liters. During exercise, the stroke volume can be increased to 120 ml or more, and the heart rate can reach 180 times per minute, so even an untrained person can output more than 20 liters per minute.

As mentioned above, if a person's maximum cardiac output is 20 liters per minute, and the muscle tissue's ability to use oxygen per 100 ml of blood is 16 ml, then his maximum oxygen intake per minute is: 20 liters × 0.16 = 3.2 liters. It can be seen that when the muscle's ability to use oxygen is unchanged, the output per minute is the main factor that determines the maximum oxygen intake; if you want to increase the maximum oxygen intake, you must increase the cardiac output. Therefore, all exercises that can increase the maximum oxygen intake and improve aerobic work capacity are exercises for the heart.

The effect of exercise training on circulatory function firstly causes cardiac hypertrophy. The results of studies on the heart area of some Chinese athletes prove that 36% of people have a heart area that is more than 10% larger than the average person, and the heart hypertrophy of marathon runners and long-distance cyclists is the most obvious. The results of the research on the athlete's heart volume also show that the cyclist's heart is the largest, followed by long-distance skiing, modern pentathlon, and weightlifting and gymnastics. This shows that the endurance program has a significant impact on strengthening heart function.

The heart rate of athletes with a strong heart slows down when they are quiet, only 36 to 40 times per minute, which is called bradycardia; as the stroke output increases to 100 ml or more, there is no change in output per minute. Such athletes can output more than 200 ml per stroke during exercise, and the maximum value of the heart rate is higher than that of ordinary people. Therefore, the maximum output per minute can increase by about 10 times to that at rest, reaching 40 liters.

It can be seen that physical activity can improve the function and working ability of the heart muscle, can also expand coronary arteries, improve heart nutrition, reduce cholesterol content in the blood, thereby preventing atherosclerosis and keeping blood pressure at normal levels.