To investigate how aerobic exercise affects the heart rate

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IB Biology SL

Lillian Teoh [12D]

Research Question

To investigate how aerobic exercise affects the heart rate of a 16 year old male. The aerobic exercise I will be using to conduct this experiment is jumping jacks, commonly known as star jumps.

It is a physical jumping exercise performed by jumping to a position where both legs are spaced out from each other while hands are placed over the head like the shape of a star, and then returning to the original position of both feet together with arms by the sides.



Independent variable:          Length of time to perform jumping jacks

Dependent variable:         Pulse rate – the time between heart beats (after every minute)

Controlled variables:

  1. Physical status
  • Height
  • Age
  • Gender
  • Weight
  • Dietary intake before exercise
  • Fitness level
  • Body size
  1. Time taken for each jump (1 second)
  2. Pulse rate before exercise (90 beats per minute)
  3. Repetition (5 times for each value)
  4. Time of exercise (4 pm)
  5. Conditions in environment
  • Temperature in environment
  • Clothing and shoes


Heart rate is the rate at which the heart beats per minute. Heart rate is measured by monitoring the pulse of a person. Every time the heart beats, it pumps a quantity of blood into our circulatory system. These beats cause a shock wave (pulse) which travels along the walls of the arteries. This pulse can be felt in several parts of the body. In this experiment, an automatic blood pressure monitor is used on the arm to measure the pulse of the test subject.

A person performing physical activity would require a higher demand for energy. In order to get more energy, respiration needs to be increased. This means that a greater amount of oxygen and glucose is required by the body which can be obtained by increasing the rate of breathing so more oxygen can enter into the system.

To meet these increased needs, more blood must be delivered to the muscles during exercise. In order for this to happen, the heart must beat faster to pump more blood to the muscles to transport oxygen and in addition remove waste products (carbon dioxide and water) in a shorter amount of time. Hence, this results in the increase of heart rate.

Based on this scientific knowledge, I can therefore predict that the heart rate will increase as the length of time performing jumping jacks increases. However, when the physical activity is stopped, the heart rate will gradually decrease back to the resting heart rate.


  1. Measure resting heart rate (before exercise) using an automatic blood pressure monitor
  2. Perform jumping jacks for amount of time indicated
  3. Immediately measure pulse using the blood pressure monitor
  4. Record pulse rate in a table
  5. Rest until resting heart rate is achieved
  6. Repeat the experiment for the next pre-set time.
  7. Repeat the experiment 5 times for each length of time.

How to use an automatic blood pressure monitor

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  1. Seat on a chair with feet flat on the ground
  2. Slide left arm through the cuff and position the cuff about 0.5 inches above the elbow.
  3. Position the green marker directly over the artery on the inside of the arm
  4. Secure the cuff
  5. Place arm on a table so that the cuff is at the same level as heart
  6. Press the start button and remain still
  7. The cuff will inflate and numbers will be displayed
  8. When the measurement is complete, the cuff will deflate
  9. The blood pressure and pulse rate will be displayed on the screen
  10. ...

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