Question

the graph represents a persons heart rate in beats per minute during 30 minutes of exercise.
cardiac exercise
which statement best describes the relationship between heart rate and time during exercise?
○ the heart rate increases for 6 minutes, remains constant for 19 minutes, and then gradually increases for 5 minutes.
○ the heart rate decreases for 6 minutes, remains constant for 19 minutes, and then gradually increases for 5 minutes.
○ the heart rate increases for 6 minutes, remains constant for 19 minutes, and then gradually decreases for 5 minutes.
○ the heart rate remains constant for 6 minutes, increases for 19 minutes, and then gradually decreases for 5 minutes.

Explanation:

1. 0-6 minutes: The line rises from 75 bpm to 135 bpm, so heart rate increases over 6 minutes.
2. 6-25 minutes: The line stays flat at 135 bpm. This is a duration of $25 - 6 = 19$ minutes, so heart rate is constant.
3. 25-30 minutes: The line falls from 135 bpm to 105 bpm. This is a duration of $30 - 25 = 5$ minutes, so heart rate gradually decreases.

Answer:

C. The heart rate increases for 6 minutes, remains constant for 19 minutes, and then gradually decreases for 5 minutes.