How exercise affects heart rate

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How exercise affects heart rate

Aim:

My aim is to find out how exercise affects heart rate.

Research:

The heart is made almost entirely of muscle. It is a hollow organ which pumps blood around the body. The heart is enclose in a sack of tissue called the pericardium. The heart is thought to have evolved from a muscular region of an artery. It is divided up into four chambers: Two atria or auricles situated in the upper part of the heart, whose function is to receive blood. Two ventricles, situated in the lower part of the heart whose function is to pump blood. The right side of the heart receives deoxygenated blood through the Venae Cavae. The blood is then pumped to the lungs were it picks up a new oxygen supply. The left side of the heart receives oxygenated blood from the lungs and is pumped out around the body. The left and right sides of the heart do not communicate.

The average human heart beats around 70 times a minute. With each beat 5 ounces of blood is pumped, or approximately 4,000 gallons a day. The heart rests in between beats so it rests more then it works, ie. in a 70 year lifetime the average human heart works for about 30 years and rests for about 40 years.

When we exercise our heart rate increases. This is because our muscles are working harder and need more energy. Our heart rate increases to supply more oxygen, carried in the blood, to these muscles. The oxygen is needed in the muscles for aerobic respiration, that is to break down glucose, which we get from food, into glycogen which is the main type of energy we use when we exercise. This can be shown in the word and symbol equations:

Glucose + Oxygen ? Energy + Carbondioxide + Water

C6H12O6 + 6O2 ? E + 6CO2 + 6H2O

Exercise can make us fitter by making our heart work harder. The heart gets bigger and rests in between beats for longer, therefore becoming more efficient. People who are not fit do not get enough oxygen pumped to their muscle even though their heart still beats fast, the muscles build up an oxygen debt. Because the muscles are not getting enough oxygen they start respiring anarobically, that is, without oxygen. This type of respiration produces much less energy then aerobic respiration and produces lactic acid. Lactic acid is what causes cramps and when we stretch after exercise it is to get our muscle back to their original shape and get rid of the lactic acid.
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Trial run:

I have done a trial run to help me plan my actual experiment as well and as fairly as possible. I am testing the same thing as in my actual experiment and will record my findings.

Method:

I will take an average of my 3 resting rates, measured in beats per minute, to make the experiment a fair test. I will then run on the spot for 2 mins and record my pulse rate straight after this exercise. I will then see how many minuets it takes for my pulse to return to ...

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