The Effects of Exercise on the Heart Rate
The Effects of Exercise on the Heart Rate
Aim: To discover if there is any link between the amount of exercise taken to the rise of a person's heart rate.
Prediction: I believe that when the body is exercising very hard, the heart reaches its maximum heart rate. In a graph it would appear like this:
When the maximum heart rate is reached the graph will level off because the heart rate is no longer increasing.
When the body is exercising the muscles respire to produce energy, so the muscles can contract. Oxygen is needed for this process; the oxygen is carried in the haemoglobin of the red blood cell. The heart and lungs need to work harder in order to get a greater amount of oxygen to the muscles for respiration. In muscle cells digested food substances are oxidised to release energy. These oxidation reactions are called cellular respiration. When muscles use oxygen in order to respire the process is called aerobic respiration:
Glucose + Oxygen Carbon Dioxide + Water
C H O (aq) + 6O (g) 6CO (g) + 6H O (l)
Energy released = 16.1kJ/g glucose
This is only when the muscles are working aerobically. For movements such as raising an arm or moving the fingers, adenosine triphosphate (ATP) a chemical form of energy, is used. When the muscles use ATP for energy a chemical process happens where the ATP is broken down into two simpler chemicals, ADP (adenosine di-phosphate and inorganic phosphate. The process of turning ATP into ADP releases the energy which gives your muscles the ability to contract. When exercising ATP is used up within the first twenty seconds, the cells use the ATP in two phases; firstly glycolysis takes place, (the breakdown of glucose to pyruvic acid, which is a form of lactic acid) and then the complete oxidation of pyruvic acid to carbon dioxide and water, which will then be carried away by the blood stream. There may then be a period when the muscles are working anaerobically, without oxygen. A waste substance of aerobic respiration is pyruvic acid; this is then converted into CO . But when anaerobic respiration is taking place the pyruvic acid is oxidised and is converted into lactic acid. The lactic acid would begin to build up from the oxidation of pyruvic acid in muscles. Muscular contractions would become difficult because lactic acid prevents the conversion of energy quickly. If the muscles continued to work anaerobically then muscular cramps would begin until finally they would not work at all. This only occurs when an extended amount of exercise has taken place and in the first few minutes of exercise.
During exercise, cell respiration in the muscles increases, so the level of carbon dioxide in the blood rises. Carbon dioxide is slightly acid; the brain detects the rising acidity in the blood. The brain then sends a signal through the nervous system to the lungs to breathe faster and deeper. Gaseous exchange in the lungs increases allowing more oxygen into the circulatory system and removing more carbon dioxide. The brain then sends a signal to the sinoatrial node to make the heart beat faster. As a result the heart rate would rise. Due to the increased intake of oxygen and heart rate the rush of oxygen and glucose to the muscles promotes oxidation of the lactic acid into CO so that it can be carried away. The muscles will then be able to work aerobically, which produces the most amount of energy per mole than anaerobic respiration.
In the resting adult the normal heart rate is around 70 beats per minute, with each cardiac cycle lasting 0.8 seconds. A person's maximum heart rate is found by:
220 - The person's age = maximum heart rate
The 'Nursing Practice Hospital and Home, the Adult' states that 'the cardiac cycle is the cyclical contraction (systole) and the relaxation (diastole) of the two atria and the ventricles. Each cycle is initiated by the spontaneous generation of an action potential in the sinoatrial node. Diastole lasts around 0.4 seconds. Increasing pressure in the ventricles closes the triaspid and mitral valves; this then means that all four valves are closed. Ventricular pressure continues to rise until eventually the pulmonary and aortic valves are forced open and blood is ejected into the pulmonary artery and aorta'. When the heart rate is increased the amount of time the diastole and systole take place is shortened, so that more blood is pumped out in one minute.
Method:
Apparatus: Stopwatch
Bench
Trainers
. To start with we measured the persons resting heart rate where there was no strain on the muscles. We decided to lie down while taking our pulse rate. If there were any strain on the muscles this would make our results unreliable because it would increase the heart rate.
2. We decided to make the length of each consecutive trial 1,2,3,4 then 5 minutes long. Between each session we allowed the persons' heart rate to return to its resting heart rate, otherwise the results would not be ...
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Method:
Apparatus: Stopwatch
Bench
Trainers
. To start with we measured the persons resting heart rate where there was no strain on the muscles. We decided to lie down while taking our pulse rate. If there were any strain on the muscles this would make our results unreliable because it would increase the heart rate.
2. We decided to make the length of each consecutive trial 1,2,3,4 then 5 minutes long. Between each session we allowed the persons' heart rate to return to its resting heart rate, otherwise the results would not be fair if the heart rate was higher at the start of a trial.
3. Then the person began to carry out the trial, we had a four beats in two seconds so that the person would not slow down or speed up which would affect the heart rate.
Immediately after exercise the person laid down so they could take their pulse rate. They took their pulse rate for 15 seconds, if we had taken the pulse rate for 1 minute the pulse rate would have slowed down. We then waited for the pulse rate to return to its resting rate before we started the next trial.
Fair Testing: Our experiment is about how the heart rate is affected by exercise. Unless we use a stethoscope we cannot measure the heart rate beat directly. We are measuring the pulse rate on the carotid artery. This will keep the experiment fair because each heart beat set up a ripple of pressure which passes along the arteries. The ripple can be felt as a pulse as the artery's muscular wall expands and relaxes. Measuring the pulse rate is measuring the hearts beats except there is a minimal lapse between the beat and the pulse. The diastole and systole produce a very distinctive two tone sound which is very easily felt. So to make sure we do not count twice we will always count the first pulse of the two.
Within a trial we have to keep the same person throughout. This is because every person has a different diet, fitness level, weight, stature or is a different gender. All these factors affect a person's heart rate. I f the person was changed during the experiment the results would not be reliable or fair. Their resting heart rate would be different and their body's reaction to exercise would also be different.
The trial must be taken on the same day. The person's health may be different or they may haven taken caffeine or medication which would artificially raise or lower their heart rate. By dong the trial in the same day, all of the body's factors are the same at one time for the trial.
The pace of the person will affect the person's heart rate. They may start off at a quick pace, but go slower when they begin to tire. Because our test uses the leg muscles repeatedly, the person must rest between each trial so that all the lactic acid and CO can be carried away. The 'tiredness' of the person's legs will affect the pace at which they step up and down. This is why it is crucial for fair results to have a beat the person keeps to throughout the trial, four beats in two seconds. It is also necessary to allow the person to recover before carrying on the trials.
We must measure the person's heart rate after exercise in the same position as when we took their resting heart rate. If we do not we will not get accurate results. If the person is standing instead of lying down while their pulse rate is being taken the heart would rise because the muscles are working to keep the person upright. The heart rate would have to work harder in order to keep the muscles working.
The equipment used must be the same. If we were to change the bench to a step, the step may be higher or lower. Making the muscles work harder or lesser to step up. The heart would then have to work faster or slower in order to supply the required amount of oxygen to the muscles.
We will change the length of exercise so that we receive a range of results. We will then be able to see how exercise affects the heart rate. The lengths of exercise will be 1,2,3,4 and 5 minutes long. Afterwards we must let the person's heart rate return to its resting heart rate. Otherwise the following trial will not provide accurate results, because the trial would have started with a higher heart rate.
Amount of Exercise (minutes)
Pulse rate per minute
0
80
26
3
28
5
68
Pilot Test:
For our pilot test we used a range of 1, 3 and 5 minutes, to test the extremes and the middle value of the experiment. This would show if the pace or length of the trial should be increased.
Throughout the test one person would be counting 4 beats in 2 seconds. The person carrying out the trial would step up to the first and second beats and step down on the third and fourth beats.
The feet of the person would be placed on the step on to the instep, so the foot would have to go farther or a shorter distance.
We decided to measure the heart rate lying down because there would be no additional stress on the heart, which would increase the heart rate. The heart rate should also return to its resting heart rate due to the decrease of muscle use.
Length of exercise (mins)
st Trial
2nd Trial
3rd Trial
4th Trial
Average
0
80
80
72
72
76
24
20
16
12
20
2
32
36
24
20
28
3
28
52
32
44
40
4
56
60
52
56
56
5
72
76
64
68
72
Results of Effects of Exercise on the Heart Rate
Pulse rate per minute (beats)
Conclusion: The graph shows that as the length of exercise increases the pulse rate raises until it starts to level off. The highest increase in the pulse rate occurs between 0-1minute. The pulse rate rises by 22 beats per minute. Thereafter it continues to rise by 21 beats every minute. When the body is exercising the muscles respire to produce energy, so the muscles can contract. Oxygen is needed for this process; the oxygen is carried in the haemoglobin of the red blood cell. The heart and lungs need to work harder in order to get a greater amount of oxygen to the muscles for respiration. In muscle cells digested food substances are oxidised to release energy. These oxidation reactions are called cellular respiration. When muscles use oxygen in order to respire the process is called aerobic respiration:
Glucose + Oxygen Carbon Dioxide + Water
C H O (aq) + 6O (g) 6CO (g) + 6H O (l)
Energy released = 16.1kJ/g glucose
The heart rate rises because during exercise, cell respiration in the muscles increases, so the level of carbon dioxide in the blood rises. Carbon dioxide is slightly acid; the brain detects the rising acidity in the blood, the brain then sends a signal through the nervous system to the lungs to breathe faster and deeper. Gaseous exchange in the lungs increases allowing more oxygen into the circulatory system and removing more carbon dioxide. The brain then sends a signal to the sinoatrial node to make the heart beat faster. As a result the heart rate would rise.
The 'Nursing Practice Hospital and Home, the Adult' explains in detail how the heart beats and how the heart would beat faster. It states that 'the cardiac cycle is the cyclical contraction (systole) and the relaxation (diastole) of the two atria and the ventricles. Each cycle is initiated by the spontaneous generation of an action potential in the sinoatrial node. Diastole lasts around 0.4 seconds. Increasing pressure in the ventricles closes the triaspid and mitral valves; this then means that all four valves are closed. Ventricular pressure continues to rise until eventually the pulmonary and aortic valves are forced open and blood is ejected into the pulmonary artery and aorta'. When the heart rate is increased the amount of time the diastole and systole take place is shortened, so that more blood is pumped out in one minute.
My graph confirms my prediction in that as the length of exercise is increased, the number of beats per minute will rise. The number of beats per minute rises steadily because the amount of exercise is gradually increased. The heart reacts to this by increasing the number of times per minute that it beats so that the muscles have enough oxygen and glucose to work with the greater amount of exercise. The only way in which my results do not coincide with my prediction is that the graph does not begin to level off. This is because the maximum heart rate was not reached during exercise. Overall my prediction has been proven correct so far that my results support my theory.
Evaluation: I believe that I have a firm conclusion. I have decided this due to a number of factors. We repeated our results three times in order to take an average which would produce more reliable results. All our results were of a similar pattern. There were none that were totally unexpected and completely went against my prediction.
Throughout the experiment I kept the following things the same to ensure reliable results: we measured the first beat of the heart,
we kept the same person throughout the trials,
the trial was taken on the same day and not in intervals,
the pace of the exercise was kept constant,
starting heart rate was always the resting heart rate,
the equipment used was kept the same.
We controlled all the above variables that could have affected our results.
Our experiment was fairly accurate, we measured the carotid artery and although this is not a direct measure of the heart, the ripple felt is directly proportional to the heart rate. So as a result by measuring the pulse rate we were measuring the heart rate.
There were areas of my experiment that would question the reliability of my results. The pace of the person carrying out the trial may have changed during the trial. Even though another person was counting the beats the exerciser may have not kept in time with the beats. A way to make sure the person would be kept at the same pace throughout the trial would be to carry out the test on a treadmill instead of steps. The pace could be kept to within a decimal place of the actual speed, greatly improving the accuracy of the results. When one trial was over, and we would be lying down relaxing so that our heart rate would return to normal, we did not account enough time for the lactic acid in our leg muscles to be carried away. We would not be able to judge if all traces of lactic acid had indeed been carried from the legs.
This would affect the following trial because the lactic acid building up in the legs would make them work slowly and eventually have cramp in the leg. This would make the person slower reducing their actual heart rate, therefore affecting our results. There would not be a certain way of assessing the amount of lactic acid in the leg muscles, they only way to make the experiment more reliable would be to increase the amount of time in between each trial. This would give the body a longer time to recover and to carry away the waste products of anaerobic and aerobic respiration.
As the trial was being carried out the body temperature of the exerciser was rising. The heat of the body would increase the heart rate which would adversely affect our results, making them less accurate and reliable. We can not control if the body heats up during exercise, only to the extent of using a fan to cool the epidermis of the skin which would lower the temperature of the blood, thus reducing the body's core temperature. This would then keep the heart rate at a more natural level during exercise.
The food consumed by the participating people may have contained different amounts of fats, carbohydrates and lipids. This would affect their available glucose levels during exercise. For example a person who had a fibre rich cereal that morning would have a higher amount of glucose readily available than a person that would have had no breakfast at all. The person with the higher stores of glucose would have not become tired as quickly as the person who had low glucose stores. A solution to this would be to control the amount food and what kinds of food that all participants ate before the trials.
After the trial had been performed the exerciser would have taken their own pulse rate. This was a very unreliable way of taking the pulse rate. They may have taken a while after the trial to find their pulse, they may have counted incorrectly, due to systole and diastole they may have ended up with half a beat when the 15 seconds was up or they may forget half way through counting. The only way to accurately measuring the heart rate would be to use a data logger. The data logger is a heart rate sensor which takes the heart rate directly during exercise. This would produce far more accurate results because the heart rate could be taken during exercise rather than after it.
Within our results we only found one result to be anomalous. This was at 1 minute; the amount of beats per minute was 120. This was a steep inclement from the resting heart rate of 76 beats per minute. From the line of best fit this particular result was out by 23 beats per minute. I think we got this result because it was the first result. When starting out the exerciser is not tired and still has stores of ATP is the muscles, so they start off quickly, making their heart rate faster to start off with. It is not until they start to become slightly more tired do they begin to slow down, which would affectively lower their heart rate; this can be seen from the 2 minute results and onwards.
To improve upon this experiment I would increase the amount of times it is repeated, to give a wider range for the average to be taken from. I would also increase the range of the results. I would make the experiment longer to be able to see if the heart rate will actually level out and at which point. I would also increase the results in between the current ranges, e.g. have a range going up in intervals of thirty seconds instead of an interval of a minute.
Further experiments I could carry out within my aim could involve exercising different muscle groups of the body. This could show which muscles need the most amount of blood supply. I could also try different intensities of the exercise carried out, for example carry out the experiment in sprinting and in badminton.
Bibliography: I have various texts and internet sites for my research, they are;
'P.E up to 16' by Linda Green and Sally Fountain, published by
'Nursing Practice Hospital and Home, the Adult' by Alan Pearson, published by Heinemann.
Various web sites.
