Design an investigation to show the effect of different types of exercise on the heart rate of athletes.

A well-designed investigation should be a fair test. * **Independent Variable:** The variable you change is the type of exercise. You should specify at least two different types, for example, jogging and sprinting. * **Dependent Variable:** The variable you measure is the heart rate, in beats per minute (bpm). This should be measured immediately after each exercise. * **Control Variables:** To make it a fair test, you must control other factors that could affect heart rate. These include: * The duration of the exercise (e.g., 5 minutes for each type). * The person or group of people doing the exercise (using the same athletes for all tests). * The rest period before starting and between each type of exercise, ensuring the heart rate returns to the resting rate. * The environmental conditions (e.g., room temperature). * **Method:** 1. Measure the athlete's resting heart rate. 2. Have the athlete perform the first exercise for a set time. 3. Measure their heart rate immediately after. 4. Allow them to rest fully. 5. Repeat for the second type of exercise. 6. To improve reliability, you could repeat the experiment with several athletes and calculate a mean change in heart rate for each exercise type.