Effect of Exercise on a Heart Rate.

Jamie Willis

Effect of Exercise on a Heart Rate

The Science

Oxygen + Glucose = Carbon Dioxide + Energy (ATP)

When you exercise, you increase the need of energy for your body. This Energy, or Adenosine Tri-Phosphate (ATP), is produced from oxygen and glucose. To get more oxygen into our body, we breathe faster, bringing more oxygen in to our lungs, and our heart rate increases, pumping this oxygen to our cells faster. The oxygen breaks down the glucose in the cells then produces the energy needed to continue your exercise. This is called aerobic respiration, meaning it uses oxygen.

If you need more energy, then the body uses a process called anaerobic respiration, which means not requiring oxygen. An enzyme in your cells breaks down the glucose into two molecules of pyruvic acid. This gives off your energy, but the pyruvic acid is broken down further into lactic acid (carbon dioxide and ethanol). Because lactic is poisonous you can only release energy like this for a short time, because it would soon begin killing off your cells. The lactic acid builds up in your muscles making them ache. To recover from the poison in your muscles you breathe deeply, this provides oxygen, which breaks down the lactic acid, into carbon dioxide and water. The amount of oxygen needed for the muscles to recover is called the oxygen debt.

Planning

Prediction

My prediction is that as I increase the length of time I exercise for the higher my heart rate will be. This is based on observations from previous exercise and a preliminary experiment in which we tested the difference in our heart rate over different amounts of time, much as we are doing here. This was at a different pace compared to this experiment though and would therefore give different results. These are the results I got from this preliminary experiment:

Method

This is a preview of the whole essay

Method

I will start my experiment by taking a record of my resting heart rate. I will do this by placing two fingers on my wrist and pressing lightly. Then I will count every beat in the space of a minute, using a stopwatch to keep the time. I’ll repeat this procedure three times to get a reliable measurement. This will give me my resting pulse rate in beats per minute (bpm); I’ll record this in my table of results. My first exercise will last one minute. The exercise I will be doing is stepping up and down from a block or stair. I will set a metronome, to 69 bpm, to keep me at the same pace each time, and use a stopwatch to check how long I’ve been exercising for. After a minute has passed, I will take my pulse for a minute and record it in the table along with my resting pulse rate. After checking my pulse has returned to its resting rate I will repeat this experiment. To ensure my pulse is at its resting rate I will rest for the same amount of time I have just exercised for, i.e. if I have worked for four minutes I should rest for four minutes before doing the next experiment. In the second experiment, I will change the time to two minutes rather than one. When finished I will record my pulse again, wait for it to return to its resting rate and then repeat the experiment for a third time, changing the length of time I’ll exercise for to three minutes. I will repeat this process until I have pulse results up to seven minutes, this means exercising for four more times.

To keep the test fair I will ensure my pulse is at its resting rate before starting any exercise. I will use the metronome to keep my steps in time and therefore not changing the rate of energy I exert. The only variable factor in the experiment will be the amount of time I exercise.

To make sure the experiment is safe I will use the bottom stair; this will reduce the damage causes if I fall compared to using the top stair. To reduce the chance I will fall I will tie my shoelaces or wear socks. If at any time during the experiments I feel unwell I will cease the experiment immediately.

Other factors we could investigate include the rate of our breathing after different lengths of exercise. The reason we chose to investigate our heart rate was because it is easier to record and provides a more interesting result.

Equipment

Stopwatch, Metronome, Table of results, Block or Stair

Results

Table of results

I repeated the measurements for resting and one minute three times and then took an average to get he most reliable result. I put all these results in my table above along with the averages. After assessing my results for three four and five minutes I have decided to repeat them too. These are the second set of results I got:

Using these new results and the one’s from the old table, I created a line graph of the different points, including a line of best fit in red:

By looking at the graph I can see there is a curve emerging. If it was a straight line it would show that my heart rate was going up at a steady speed and would continue going up, whereas this curve shows when I started my heart rate increased the most and then as I reach the peak speed for my heart to pump it will settle out. This is because there is a limit to how fast the heart can pump and when it reaches it highest speed no more oxygen than is already being pumped can be. Therefore the lactic acid will not be broken down and will eventually cause the muscles to ache so much the exercise will have to cease.

This graph shows the difference between one session of exercise and the next. A tall bar shows there was a high change in the heart rate compared with the previous exercise session, whereas a short bar shows little change. You can see that during the first 4/5-minute exercise sessions there was as large change, but as I exercised for longer my heart rate started to settle at a constant rate. This proves that a heart rate doesn’t increase forever but simply levels out and stays they same. They level that my heart rate started settling was at 160 bpm. A fit athlete would have a much higher level because their heart would cope with it easier and would therefore pump more oxygen around their body allowing them to keep going that much longer.

Evaluation

The experiment went well but did encounter a few problems. The first of which was the absence of a stopwatch, but watching the second hand of a clock and simply counting the minutes easily resolved this. Another change I made to my experiment was not to use a basic metronome, but in stead a drum beat from a keyboard, this proved just as good as method of keeping in time.

I expect my results to be fairly accurate, my first result, when viewed on my difference’s graph seemed more similar to the second than as I expected. This may have been because I made a mistake when recording my pulse rate or simply because my heart rate stays similar during the first and second minute of exercise.

If I was to repeat this experiment I would make sure I had a hand held stopwatch or alarm, which would make it easier to check my time, than using the second hand of a clock. I could have worked with a friend, rather than doing it all on my own. This would have made it easier to concentrate on the exercise rather than worrying about how much longer I had to cary on for.

Sources