Let us do a few facts check before we begin with this post. Do you know that the human body has about 34 trillion cells which functions for years just to keep us alive? [1]. These cells include blood cells, nerve cells, stem cell, Bone cells, skin cells, muscle cells, endothelial cells, Fat cells, and egg cells. Some of these cells are transported via Arteries, veins, and capillary. The human arteries, veins, and capillaries, when measured, is over 60,000 miles long (just long enough to round the world twice). [2]. The heart is not one big organ, in fact, it isn't bigger than a fist, (10 ounces in men, and 8 ounces in women), but it is the most important organ of the body. All other organs, tissues, and cells are important, but they all depend on the heart to function. The heart beats about 100,000 times in a day, pumping 2000 gallons of blood through the veins, arteries and capillaries, to other part of the body daily [3].
The cells need oxygen, and so are the organs in the body, and in other to get this oxygen to the body, the heart pumps oxygenated blood to all part of the body. The heart pumps blood through the left ventricle (the most powerful chamber of the heart) to the entire body, and to the lungs, through the right ventricle. [4][5]. When the heart contract, the left ventricle pumps blood through the aortic valves into the Aorta. The Aorta is the largest artery in the human body, since it collects blood in large amount. If you want to understand how big the aorta is, it is about 2 cm wide, like the average hose.[4][6]. The Aorta branches into other arteries, the arteries branches into arterioles, and the arterioles branches into capillaries. The Capillaries allow for exchange of bloods between the tissues and the bloodstream.
When the blood is returned to the vein, it goes back to the right Atrium, which then sends the blood to the right ventricle. The right ventricle, which isn't as thick as the left ventricle, sends the deoxygenated blood to the lungs for oxygenation (pulmonary circulation). The lungs return the oxygenated blood to the left Atrium, which then goes to the left ventricle, which pumps the blood to the body.
Now that we are done with the fact check and explanation, let me go to the purpose of this post, which is to understand how the heart functions during exercise. In our world today, we can sit down for hours without moving anywhere, just working on the laptop and on the internet. Some people spend their entire day sitting in place doing remote jobs, but does the body want us to sit down all day, without moving?
Sitting more in a day can cause a lot of illness in the body. According to the article Sitting Less and Moving More: Implications for Hypertension, the risk of moving our body usually affects the heart more. First, it does not allow for the regulation of blood-glucose causing high blood-sugar, it allows for excessive fat to be stored in the body causing obesity, hypertension, cancer and type 2 diabetes. [7][8]. Muscles play an important role in blood movement in veins. The veins are compressed when the muscles are contracted, thereby causing an increase in the pressure of the blood back to the heart.[9]. When we do not exercise, cholesterol is deposited in the arteries of the heart, causing clogs, which would cause coronary diseases.[10].
For clarity, the heart pumps oxygenated to the body both during exercise and when we aren't exercising, but during exercise, the tissue demand for more oxygen, and the heart has to pump more blood to that area. When the femur isn't doing any exercise, the blood flow in the femoral artery at rest is at an average of 3 milliliters per min (0.3 L min(-1)) per 100 gram of tissue, and the blood flow could increase to 6-10 L per minute, per 100 gram of tissue.[11].
In other, to perform the function of pumping by the heart to the muscles during exercise, the cardiac output is increased, peripheral arterioles vasoconstrict, and a constriction in the veins of the muscles.
Cardiac output as the name implies, is the total amount of blood, pumped out of the heart. The cardiac output of the heart is determined by the heart rate and stroke volume. The heart, during exercise, beats faster (heart rate), and also the stroke volume (which is a result of how hard the left ventricle pumps blood during each beat) as a result of the left ventricle contraction doubles.
Arterioles and arteries during exercise, in other to decrease the flow of blood to places not needed, the arterioles and arteries connected to those organs and regions constrict, while the arterioles connected to the muscles will be dilated so more blood can get into the muscles. Also, while the arterioles are dilated, the muscular veins are constricted, and this makes the vein to pop out during exercise.[12].
The heart, being a unique organ, pumps blood to both the body and itself. The blood is pumped to itself, through the right and left coronary arteries. The blood is gotten from the Aorta first before other part of the body gets blood. People who do not exercise frequently are prone to heart attacks than people who exercise. This is because, cholesterol [plaques] can cause blockage in the heart muscles, which could lead to a heart attack when these muscles die.[10][13]. The heart muscles, unlike other muscles in the body, do not regenerate, when they die, dead/scar tissue grow at the site making it difficult for the heart to pump.
On an average, I sit for about 13 hours, which involve periods when I sat at the office, eat, watch movies, chat on my phone, shuttle back home. While sitting, my body isn't doing a lot of activities and that makes my body burn fewer calories, up to about 80 calories/hour, compare to when I am standing [about 88 calories/hour], and when I am working [about 210 calories/hour].. According to the American Cancer Society Study, sitting for a long period of time is associated with a 19% higher rate in the cause of death in the United States, and a conclusion from the article Daily Sitting Time and All-Cause Mortality: A Meta-Analysis, confirms that higher amount of sitting could lead to greater risk of all-cause mortality commonly from Cardiovascular Diseases. I ensure I spend 1 hour on exercise per day. How long to do exercise, stay sitting or standing?
Reference
[1] National Geographic - How Many Cells Are In Your Body?
[2] Cleveland Clinic - How Does Blood Flow Through Your Body
[3] WebMD - Amazing Facts About Heart Health and Heart Disease
[4] Health Line - Left ventricle
[5] Health Line - Right ventricle
[6] Michigan Medicine - Does an Enlarged Aorta Always Mean Surgery?
[7] NHS - Why we should sit less
[8] National Library of Medicine - Sitting Less and Moving More: Implications for Hypertension
[9] Medicine libretexts - Blood Flow in Skeletal Muscle
[10] Mayo clinic - Coronary artery disease
[11] National Library of Medicine - Skeletal muscle blood flow in humans and its regulation during exercise
[12] Mens health - Are Veiny Arms Really a Sign You're Super Fit?
[13] Clevelandclinic.org - Coronary Arteries
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