Skip to content
Dabour HubLEARN · PRACTICE · EXPLORESign inStudent

7.4.2Topic 7 · Run for your Life

Practical- Investigating the Effects of Exercise — Edexcel A Level Biology A (SNAB) 9BI0 Revision Notes & Topical Questions

5 min read 8 parts Lesson 22 of 25 1 quiz

📚 Edexcel A Level Biology A (SNAB) 9BI0 Hub / Topical Revision
🩺
100% Curriculum Specification Match Lesson Doctor Verified
The only platform with 100% curriculum specification match and verified interactive question banks.
0%read
Lesson summary

7.4.2 Practical- Investigating the Effects of Exercise — Edexcel A Level Biology A (SNAB) 9BI0 notes: Plan, carry out and evaluate an investigation into the effect of exercise on heart rate or breathing, and process the data.A typical investigation tests the effect of the intensi…

  • spirometer
  • Tidal volume
  • Breathing rate
  • Oxygen uptake
  • Exam-style question 1
  • Exam-style question 2

Section 1 of 8Aim and hypothesis

A typical investigation tests the effect of the intensity of exercise on heart rate or ventilation.

Aim and hypothesis
A suitable hypothesis is: as the intensity of exercise increases, the heart rate increases.
The null hypothesis is that there is no significant difference in heart rate between different exercise intensities.
Human participants must give informed consent, be told they can stop at any time and be healthy; people with heart or breathing conditions,
  • such as asthma, should not take part in strenuous exercise.

Section 2 of 8Method for heart rate

1
Participants sit and rest for several minutes.
  • Take the resting heart rate by counting the pulse at the radial artery (wrist) or carotid artery (neck) for 30 s and doubling it,
    • or use a pulse monitor or heart rate sensor.
  • Repeat three times and take the mean.
2
The participant exercises at a set level, such as stepping on and off a step at 15 steps per minute, using a metronome to keep time, for 2 minutes.
3
Immediately record the heart rate.
  • Then record at 1-minute intervals during recovery until it returns to the resting rate.
  • Note the time taken to recover.
4
Repeat after resting at a higher intensity (such as 30 and 45 steps per minute),
  • or with the participants running on the spot or using a bike with adjustable resistance.

Variables to be controlled are the same participants (or similar age, sex and fitness), time of day, temperature, duration of exercise, height of step and recovery time between trials. The independent variable is the intensity (rate of stepping); the dependent variable is heart rate (beats per minute).

Section 3 of 8Method for breathing using a spirometer

A spirometer with a nose clip and mouthpiece records the volume of air breathed.

1
The chamber is filled with medical-grade oxygen, with soda lime to absorb CO2.
2
As the participant breathes in and out, a pen on a rotating drum or a data logger records the volume.
3
As oxygen is used, the total volume in the chamber decreases, giving a falling trace.
4
From the trace read:
Tidal volume
Tidal volume from the height of each wave (peak to trough).
Breathing rate
Breathing rate from the number of peaks per minute.
Oxygen uptake
Oxygen uptake from the slope of the line drawn through the peaks: gradient = change in volume ÷ time (dm3 min-1).

Safety precautions

  • sterilise the mouthpiece or use a disposable one between participants, make sure the soda lime does not enter the breathing circuit, and ensure no one holds their breath or hyperventilates.
  • Do not use the spirometer with anyone who feels dizzy.

Section 4 of 8Processing and evaluating

Calculate means of repeated readings at each intensity, plot a graph (intensity on the x axis, heart rate on the y axis) and describe the trend, including figures.

1
Calculate the percentage increase from rest: (exercise rate − resting rate) ÷ resting rate × 100. Recovery time is a measure of fitness.
2
A correlation coefficient or a t-test can be used to see if differences between groups,
  • such as trained and untrained people, are significant (p < 0.05).

Limitations include the small size of the sample, variation between individuals, error in counting a pulse manually, and anxiety that raises resting heart rate. Improvements include using an electronic heart rate monitor, using larger samples and repeating trials. Systematic errors can be reduced by calibrating the apparatus. Ethical considerations also apply: consent, right to withdraw and confidentiality of results.

Section 5 of 8Reporting the conclusion

A good conclusion states the trend with numbers, links to the biology and comments on reliability.

1
For example: the mean heart rate rose from 72 beats per minute at rest to 104, 128 and 151 at the three step rates,
  • so the data support the hypothesis that heart rate increases with intensity.
2
The explanation is that greater muscle activity raises CO2 production,
  • which is detected by chemoreceptors,
  • leading to greater sympathetic stimulation of the SAN.
3
If standard deviations overlap, the difference may not be significant and should be tested statistically before any claim is made.
4
Use the correct unit throughout, and remember that three or more repeats are needed to identify anomalous results,
  • which can be excluded and mentioned in the evaluation.

The same approach can be used to investigate the effect of exercise on breathing, or the effect of fitness: compare recovery times of trained and untrained participants, controlling the workload so the difference is due only to fitness.

Section 6 of 8Exam-style questions

  1. A participant has resting heart rate 68 beats per minute and a rate of 142 beats per minute after exercise. Calculate the percentage increase. [2]2 marks

  2. State three variables to be controlled in an investigation into the effect of exercise intensity on heart rate. [3]3 marks

  3. Describe how a spirometer trace can be used to find a person's oxygen uptake. [3]3 marks

Section 7 of 8Key terms

TermMeaning
Resting heart rateHeart rate measured when seated and relaxed
Recovery timeTime for heart rate to return to resting value after exercise
PulsePressure wave in an artery caused by each heart beat
Independent variableFactor changed by the investigator
Dependent variableFactor that is measured
Informed consentAgreement given by a participant after being told the risks and procedure
SpirometerApparatus to record breathing volumes and oxygen uptake
Null hypothesisStatement that there is no significant difference or relationship

Section 8 of 8Exam technique

1
Not allowing the heart rate to return to resting level between repeats.
2
Counting the pulse for a short time and not taking the mean.
3
Saying 'the same exercise' is the independent variable: the intensity is what is changed.
4
Forgetting soda lime in the spirometer, so that the oxygen uptake is not measured.
5
Ignoring ethical matters when using human participants.

Last updated: