To investigate factors which affect pulse rates when exercising.

Also when I have reached my highest measurement that my pulse will reach my graph should rise and then go in a straight line

e.g.  

This will show that I have reached my plateau. A plateau means that you have reached your total pulse rate and it cannot go any higher.

This is what I predict will happen in my investigation.

Plan:

My apparatus during the experiment will be

 

• a skipping rope

• a timer

I will take my resting pulse by using my fingers on my wrist and then start skipping for 30 seconds, after I have finished exercising I will take my pulse and record the result, next I will keep checking my pulse every 30 seconds to see when it is back down to resting.

My five measurements will be

• 30 seconds of skipping
• 60 seconds / 1 minute
• 90 seconds / 1 minute 30
• 120 seconds / 2 minutes
• 150 seconds / 2 minutes 30

After I have finished my skipping I will time my pulse for 10 seconds and then record the result, for every 30 seconds after that I will time my pulse rate for a further 10 seconds and count the time it takes to get back to resting pulse.

I will make my test fair by

• taking 3 measurements each time and finding the average – I will do this because it makes the test fairer and more accurate
• staying at a steady speed of skipping each time – I can do this by doing on jump per second.
• staying on the same surface during my experiment
• making sure that my pulse is back to resting in between each measurement

These will help make my test a fair test because it makes sure that all the other key factors are controlled.

Results:                                                                                              Time of skipping          Pulse rates                                          Average

The measurements in pink are the ones that I re-did because they were anomalies and did not fit the trend.

Time taken for Pulse rate to get back to normal:

                                                                                Average

Conclusion:

My graph shows me that my investigation went well as the shape tells me that I have reached my plateau, which is what was expected. The factor I chose made my pulse rate go up as I was exercising because the cells were respiring and needed more oxygen to produce energy for my muscles to work. The graph shape is like that of my predicted one because my pulse rate went up rapidly and then reached its final target, my results also show this. I reached 174 beats per minute quite quickly and as I did the rest of my exercises it stayed at 174.

From my results I can see that as I increased the exercising time, my pulse rate went up and so did the time that it took me to get back down to my normal pulse rate.

My pulse rate went up to repay the oxygen debt. If my pulse rate had not gone up this would have showed me that my muscles were not working on oxygen but they were producing lactic acid instead. This would have made my legs feel rubbery and sore, but as the cells were making the heart work faster this did not happen and my pulse did go up. Therefore I was using aerobic respiration and anaerobic as well; considering that my muscles became weak after a while and I had to get my breath back. This shows that the lactic acid had built up within my muscles, anaerobic respiration was occurring at this time. There were no other body changes apart from that my body felt limp but this was also because of the lactic acid in my muscles.

        My plateau shows me that after a certain amount of time my pulse rate will not go up any higher and I have reached my target. I think that at my plateau I may be using anaerobic respiration because I am having to breathe in a lot more than usual to repay the oxygen debt. My pulse rate would go neither up nor down if I were to carry on exercising. Those who did not reach a plateau have not reached their final pulse rate and need to carry on exercising to find out at which point their pulse rate would stop going up.

        I also noticed that as my pulse rate went up the time of resting and getting back to my resting pulse went up. This shows that the body was taking in more oxygen for aerobic respiration but also that more of the lactic acid was being produced and so it took longer for the oxygen to oxidize the lactic acid. I had to breathe deeply after exercising to get a lot of oxygen in at a time.

        I think that I was using anaerobic respiration more than aerobic. This is because the aerobic respiration takes longer to produce energy, although it does produce more, but anaerobic respiration produces little energy in a fast amount of time. For sustained exercise it would be easier to use both anaerobic and aerobic respiration because, although anaerobic makes you tired an feeling weak it is easier to produce, but aerobic is harder to produce but gives you lots of energy. Anaerobic respiration is easier for producing energy when exercising but there is very little energy and there is a build up of lactic acid because of an ‘oxygen debt’, this then has to repaid with oxygen after exercising.

Evaluation:

        In my results I found that I had one anomalous result, I think this was because I did not do the exercise properly and I did not concentrate; I may have been laughing or lost the skipping rope and so accidentally gave myself some resting time during the practical. This would have made the test unfair so I decided to do the time again and got a better fitting result the second time round.

        I think that my experiment was fairly accurate because I have done the measurements 3 times and found the average and I have considered the anomalous results and re-done them. My results are consistent and finally reach a plateau, which shows that I did reach my final pulse. My results are not scattered and the line of best fit was easy to find as my graph results were in the right order and they were very reliable.

        Some of the factors that could have made my results inaccurate would be that I did some exercising one day and some on another, this may have changed it because the environment around me might have been different also whether I had eaten before and what I was wearing could also affect it. Another is that halfway through I took my jumper off as I was getting hot, cooling down might have affected my results. I kept laughing and that was tiring me as well so this may have affected them, to solve this you would have to concentrate very hard and try not to laugh. I also kept losing the skipping rope out of my hands and it fell on the floor, wasting time and giving me some resting time. I tried to keep going without the skipping rope every time that I lost it or I would add some extra time onto the end to make sure that I did the full time so it would be accurate.  

        To improve the results even more you could get an electric pulse reader so that it would be very accurate and you would know exactly when you were back to resting pulse and when you had reached your plateau. That would be very simple and would make your results very accurate. You could make sure you were in a room that stayed the same temperature at all times and you could make sure you had enough time on one day so the experiment did not carry onto the next. Also you could have an electric skipping rope which you would not have to use yourself and it would keep the same pace all the way through so you didn’t speed up or slow down. Or you could change the type of exercise that you knew you could stick to the same pace and do without messing it up e.g. without losing the skipping rope.

        Overall my results were consistent but could do with some changes to make it accurate, like using the electric pulse reader and concentrating more.

Charlotte Torrance

10.1C Mrs Marriott