**Method:**
1. Select a group of athletes of similar fitness levels.
2. Measure and record the resting heart rate of each athlete before they begin any exercise. This can be done by measuring their pulse for 60 seconds.
3. Ask the athletes to perform the first type of exercise (e.g., jogging) for a set duration, for example, 5 minutes. The intensity should be controlled (e.g., using a treadmill at a set speed).
4. Immediately after the exercise, measure and record their heart rate again.
5. Allow the athletes a sufficient rest period until their heart rate returns to its resting rate.
6. Repeat steps 3-5 for other types of exercise (e.g., sprinting, cycling, weightlifting), keeping the duration and rest periods the same for each.
7. Calculate the mean increase in heart rate for each type of exercise.
8. Compare the mean increases in heart rate to determine which type of exercise has the greatest effect.
**Control Variables:** Duration of exercise, intensity of exercise (where possible), rest period between exercises, the athletes used.
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.
Expert