Heart Rate PAG PDF

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Summary

An experiment write up on how exercise affects heart rate....

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PAG 11 – The Effect of Exercise on Heart Rate Hypothesis Null Hypothesis: for the people tested, there is no significant difference between mean heart rate at rest and after exercise, any correlation is due to chance. Alternative Hypothesis: for the people tested, there is a significant difference between the mean heart rate at rest and after exercise, not due to chance. Method 1. 2. 3. 4. 5. 6. 7. 8. 9. 10.

Ensure subject is a healthy young adult and has been sitting still for at least 5 minutes. Find pulse point and count pulse for 30 seconds, double for beats per minute (bpm), add to results table. Walk on the spot/around the room for 5 minutes. Find pulse point and count pulse for 30 seconds, double for beats per minute (bpm), add to results table. Alternate between running on the spot for 1 minute and jumping jacks for 1 minute. After 5 minutes find pulse point and count pulse for 30 seconds, double for beats per minute (bpm), add to results table. Repeat for 4 other healthy young adults. Calculate mean heart rate at resting, low intensity and high intensity. Calculate standard deviation and plot results on a graph for comparison. Using a t-Test, calculate if difference is due to chance or not.

Results Table Subject

Resting heart rate (bpm)

1 2 3 4 5 Mean Standard Deviation

60 52 58 58 90 63.6 15.06

Heart rate after low intensity exercise (bpm) 104 100 96 74 106 96.0 12.88

Heart rate after high intensity exercise (bpm) 126 115 122 104 122 117.8 8.67

Calculations Mean (

´x =

´x

Standard Deviation (sx)

)

√(

(Σ x ) n

x = value n = number of values in sample ∑ = sum of

sx =

´x = = 63.6

Low Intensit y High Intensit y

Graph

´x = = 96.0

´x = = 117.8

( 60 + 52 + 58 + 5

n−1

)

t=

x = value n = number of values in sample ∑ = sum of

´x Resting

∑ ( x−´x )2

t-Test (t)

= mean

sx = = 15.06

√(

( 126 + 115 + 12 5 sx = = 8.67

5−1

√( (√ ∑

( 104 + 100 + 96 5 sx = = 12.88

∑ ( 60− 63.6)2 +(52 −63.6 )2+(58−6 ∑ ( 104 −96) 2 +( 100− 96)2 +(96 −96 5−1

√(

)( )

s1 2 s 22 + n1 n2

x = mean s = standard deviation n = number of values in group 1 or 2 = group being referred to 1: Rest & 2: Low Intensity

t=

63.6−96.0

√(

2

)(

15.06 12.88 + 5 5

2

= - 3.656 (ignore minus)

1: Rest & 2: High Intensity

t= 2 2 ( 126− 117.8) +(115−117.8 ) +(1

´x 1−´x2

63.6−117.8

√(

)( )

15.06 2 8.672 + 5 5

= -6.974 (ignore minus)

)

A graph showing how exercise affects heart rate 140

Heart Rate (beats per minute)

120 100 80 60 40 20 0

Resting

Low Intensity

High Intensity

Exercise Type

Conclusion Using the critical value table to the left and the degrees of freedom (5+5-2=8), the obtained value must be larger than 2.306 to reject the null hypothesis. Both 3.656 and 6.974 are larger and therefore at a 5% significance level the H0 can be rejected, meaning that exercise does have a significant impact on heart rate for these people, at both low and high intensity. As the graph shows, the mean heart rate increases as the intensity of exercise does, with the mean resting heart rate at 63.6 bpm while high intensity has a mean of 117.8 bpm. This is due to the heart needing to pump blood around the body faster to supply cells, particularly muscle, with oxygen to respire aerobically or breakdown lactic acid build up from anaerobic respiration during high intensity and to remove waste carbon dioxide. As well as this, the standard deviation decreases as intensity increases, showing that the subjects have a wider variety of heart rates during rest but all become closer to the mean (and each other) during high intensity exercise. However, the standard deviation is quite large for all the exercise intensities, but could become more repeatable if the number of subjects was increased. How the heart is controlled by nerves During exercise the sympathetic nervous system is activated. Chemoreceptors in the aorta, carotid artery and medulla detect a chemical change of the blood: low oxygen, high carbon dioxide and low pH due to respiration. The chemoreceptors send an impulse to the medulla in the brain, which then travels along the accelerator nerve. This leads to noradrenaline being released and binding to receptors on the SAN, trigger cardiac muscles to contract faster and therefore increase the heart rate to return oxygen, carbon dioxide and pH levels back to normal. After exercise the parasympathetic nervous system is triggered as the body is no longer so active. Baroreceptors detect the high blood pressure in the aorta and vena cava, sending an impulse to the medulla. This then travels along the vagus nerve and acetylcholine is released. Once Ach binds to SAN receptors, the cardiac muscle contracts slower to lower the heart rate and reduce blood pressure. These are both examples of negative feedback....