Question

the graph represents a persons heart rate in beats per minute during 30 minutes of exercise.
which statement best describes the relationship between heart rate and time during exercise?
the heart rate increases for 6 minutes, remains constant for 18 minutes, and then gradually decreases for 6 minutes.
the heart rate increases for 6 minutes, remains constant for 18 minutes, and then gradually increases for 6 minutes.
the heart rate decreases for 6 minutes, remains constant for 18 minutes, and then gradually increases for 6 minutes.
the heart rate remains constant for 6 minutes, increases for 18 minutes, and then gradually decreases for 6 minutes.

Explanation:

1. Analyze the graph's first segment: Starts at 75 bpm, rises to 135 bpm over 0 to 6 minutes (increase).
2. Analyze the middle segment: Stays at 135 bpm from 6 to 24 minutes (24-6=18 minutes constant).
3. Analyze the final segment: Drops from 135 bpm to ~100 bpm from 24 to 30 minutes (30-24=6 minutes decrease).
4. Match this pattern to the given options.

Answer:

The heart rate increases for 6 minutes, remains constant for 18 minutes, and then gradually decreases for 6 minutes.