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How The Human Heart Works For Athletes and Coaches

THIS IS YOUR HEART AS IT LOOKS IN THE BODY! …Well not exactly. Most people understand that this is not exactly a accurate depiction of what your heart actually looks like. So where did this come from and why is the heart thought of when speaking the word “love” or other words of that nature? Ancient mythology associated the heart with the divine and most stories show that the heart was an organ that was connected to the heavens or to god. Why exactly they thought this is not quite clear but one idea is that maybe because the heart was thought of as the middle of the body where everything originated from. Philosophers such as Aristotle believed that the heart was the center of emotion and passion which is associated with the colour red. As for the shape, there are a few leading theories. One is that it represents some of the sexual reproductive organs of the female body which was highly valued in the ancient times much more then the male counterparts. Another theory is that the heart symbol came from a seed of the Silphium plant which was used then for a contraceptive. Some believe that these two theories intertwined and that the heart symbol originated in Pompeii as sexuality was at a peak and tattoos symbolizing women’s sex organs was popular. It is believed that many were embarrassed to explain the importance of the tattoos and just said it was a symbol of “love” as to not get judgmental looks. These are theories and I can not account for the validity of these ideas; just thought it was interesting. Of course we could all be over thinking things and in fact the heart could be a quick drawing of the real thing just like a smiley face is suppose to be a persons facial expression during a happy moment. Neither are too accurate but they are both simple in our busy lives and serve the purpose. Imagine drawing out the real diagram below every time you wanted to say you loved someone via text message :p.


Below is the picture of the real heart as scientists see it today. I will not go into detailed definitions as we have a lot of information to cover. Long story short, the heart is 4 chambers that have doors connecting them that let blood pass in and out in a particular fashion to get oxygen into the body and to the other organs.

Below is a picture of the blood flow of the heart which will help explain the above diagram.

Blue=DEOXYGENATED ( no oxygen)

Red=OXYGENATED ( with oxygen)

Simply the air goes from the mouth into the trachea (wind pipe) and goes into the lungs where the oxygen is absorbed and put into the arteries ( right of the picture) where it is taken to the left atrium and pushed into the left ventricle. From there it is pushed through the aorta and circulates to the rest of the body. Once it gets to a region of the body that uses the oxygen then the blood is oxygenated and is sent back to the heart on the right side and goes into the right atrium. Then it is passed into the right ventricle and then to the lungs and the process starts all over again:)

So how does the heart actually move the blood? Well because the heart is one big muscle it contracts different parts at different times to force blood into the different chambers. You can think of it like squeezing all that juicy sugary liquid out the end of your popsicle. By squeezing one end(contracting) you for the liquid (blood) to go to somewhere that is not as narrow, ie your mouth, or in the case of the heart, the next stage of the cardiac cycle. Lets get into a little more detail however because that’s where the questions really get answered.

The heart is made out of regular muscle cells however in between these cells lay what scientists call intercalated disks which help to conduct electricity in the heart. This allows the heart to contract as a unit and squeezes the individual parts of the heart in an orderly fashion. If this does not happen appropriately then the heart starts randomly contracting different parts at different times and the cycle above gets all messed up and then the body fails to get oxygen to all its important organs including the heart it’self and you go into a state of fibrillation which basically means out of control random contractions. This is bad. Unless you have an automated external defibrillator (AED) on hand regularly then you don’t want this to happen. So how is the heart suppose to contract?

Well it all starts in the Sinoatrial Node (SA Node) which is a bundle of cells that actually create an action potential ( electrical signal). This is sort of a lie however. The heart is stimulated by the vagus nerve which originates in the head and controls heart rate. The vagus nerve does not always have to send a signal however unless there has to be a change in the heart rate so that is why it is said to create it’s own action potential. The SA node quickly starts up a signal and that causes the right atrium to contract forcing all the blood to go into the right ventricle. Then the next node known as the AV node (atrioventricular node) is fired up. There is a delay between the SA and AV node due to the fact that the right ventricle needs time to fill up. If it does not fill up then not enough pressure builds up in the ventricle to open the next door way which leads to the lungs. Therefore no blood gets tot he lungs and no oxygen gets into the blood and your dead. So let’s assume you have a normal delay and the ventricle fills up fully and the atrium is now empty. The ventricle is building pressure and eventually there is enough pressure that the next doorway, known as a valve. To help the blood have enough velocity to actually reach the lungs the ventricle is contracted by three other groups of “electrical cells”. “Electrical cells” is not a proper name, I just am at a loss of what to call them. But anyway, these three distinct areas are called, the bundle of his, name after Jr. Wilhelm His who discovered them, Bundle Branches and Purkinje Fibers and are activated in this order after the SA and AV node. The electrical signal goes around the apex (bottom pointy part) of the heart and travels to to right atrium where the process starts again.

The blood now after one cycle is in the lungs picking up oxygen and is forced back into the left atrium this time where the same cascade of signals occurs and the same happens on the left side. It must be noted that the right atrium has already filled up with new oxygenated blood and the second signal starting from the SA node is the same signal that contracts the right and left atrium. So as new blood is going back into the ventricle for a second time the left atrium is contracting and the blood that we spoke of in the first cycle is forced into the left ventricle at the same time. As the AV node node contracts the new oxygenated blood is being pushed into the left ventricle as the unoxygented blood is pushed into the right ventricle. Then both ventricles contract and blood leaves both ventricles and half goes to the lungs again to be oxygenated and the other original half of the blood we started with is now ready to go to the rest of the body and is pumped out of the left ventricle into the aorta which you can see at the top of the diagrams above.

I understand that this may be confusing so I have posted a link that shows a video from youtube. This is more of a visual concept so do not worry if you found the above explanation hard to follow.

But anyhow this cycle repeats for about 80 years or whenever you die. This is the only muscle that has enough energy to sustain systematic contraction for this amount of time without having to take a break. One reason for the extra energy output and duration is because of the increased amounts of mitochondria which is the section of the cell that is responsible for creating energy for the cells.

SIDE NOTE: wouldn’t it be cool if we could take heart cells and inject them into the legs and have ultra ultra ultra ultra endurance athletes? Unfortunately we do not know how to get past the defences of the body. The body has glycoproteins on the exterior of cells that helps the body to tell if it is a foreign particle or not. If we were to try and take heart cells and inject them into different parts of the body the cells would get rejected and kill the cells. Maybe one day though.

The last thing I want to cover is the Electrocardiogram (ECG).

This is a normal ECG reading. The important parts are already labeled. Atrial depolarization means the contraction of the right and left atrium. Ventricular depolarization is the contraction of the ventricles and ventricular re polarization is the electrical signal going to the backside of the heart back to the SA node where it starts again. Cardiology is very interesting but I am tired so I will make an article about that later. These basics must be understood before I get into that stuff anyways so I will give people time to digest this first.

Before I forget, the “U” wave is nothing really and normally does not even show up on a normal ECG unless there is a problem. Do not worry about that right now like I said. Just know the blood flow, electrical conduction and anatomy.

So let me just end of this article with some common questions.

1) What does the sound of the heart represent?

A: the “LUB” “DUB” sounds refer to the different valves opening and closing. Lub is the sound heard when the valves that lead into the ventricles close at the same time when blood leaves each atrium. The right valve is called the Tricuspid Valve ( three flaps) and the left valve is called the Bicuspid (two flaps) or mitral valve. The DUB sound is the semilunar valves (Aortic and Pulmonary) closing as blood leaves the ventricles.

2) Why is good blood pressure said to be 120/80 mmhg?

A: Systolic Pressure is the top number (120) and is the amount of pressure in the aorta when the ventricle releases the blood into it. A low systolic pressure means the heart does not pump hard enough and there may be a problem with the muscles around the ventricles. Diastolic Pressure is the bottom number and measures how much pressure is exerted on the aorta when the left ventricle is closed, ie just before the quick increase in pressure due to blood rushing out of the ventricle. This is found to be about 80 mmHg and is lower because the semilunar valve is closed for that short period of time. If this number is high then it could mean many things but one could be that you have a problem with your aortic semilunar valve which actually causes the blood to leak out at the wrong times which would account for the increase in pressure. If either of these numbers are low it means your heart is probably not strong enough. If these numbers are too high it may mean that you have a block in the heart or artery somewhere meaning the heart actually has to work harder to get the same amount of blood to the rest of the body.

3) What is the best way to prevent blocking of arteries?

A: EXERCISE!!! Yes diet is a huge factor but cholesterol is broken down with exercise. If you exercise like a maniac then it really does not matter what you eat. You will break down all build ups before they affect you. As long as you get a appropriate amount of vitamins and hit up every food group regularly then the “extra” Popeyes or dairy queen wont hurt your heart. By exercising you actually increase the thickness of the ventricles which is called left ventricular hypertrophy (LVH) and the blood will be pushed out of the heart quick enough that nothing has time to build up on the walls of your arteries. There are also proteins that are released that aid in this but that’s for a different article.

4) What does an AED do?

A: the AED sends a shock to the SA node and restarts it kind of how you shut down and computer and restart it. It happens very quickly and re balances the out of control signals of the heart. It does not always work however


So there it is, the basics of the heart. I will be going into further detail about heart conditions and ECG readings and strength and conditioning applications later. The picture above is very common and you should know it well. In later articles I will dissect this concept and show you why it matter. Enough for one day I think :)

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Greg V Roe.

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