If person is running on a treadmill, the duration of his cardiac cycle will be

Options

A. greater then 0.8 sec
B. less than 0.8 sec
C. equal to 0.8 sec
D. close to 1.0 sec

Answer

To determine the duration of the cardiac cycle for a person running on a treadmill, we need to understand the relationship between heart rate and cardiac cycle duration.

### Step-by-Step Solution:

1. **Understanding Cardiac Cycle**: The cardiac cycle refers to the sequence of events that occur in the heart during one complete heartbeat. It includes the contraction (systole) and relaxation (diastole) phases of the heart.

2. **Normal Heart Rate**: A normal resting heart rate for an adult is typically around 60 to 100 beats per minute (bpm). For our reference, let's consider a normal heart rate of 120 bpm, which corresponds to a cardiac cycle duration of approximately 0.8 seconds.

3. **Effect of Exercise on Heart Rate**: When a person exercises, such as running on a treadmill, their heart rate increases to supply more oxygen to the muscles. During intense exercise, heart rates can rise to between 140 to 160 bpm.

4. **Calculating Cardiac Cycle Duration**: The duration of the cardiac cycle is inversely related to the heart rate. As the heart rate increases, the duration of the cardiac cycle decreases.

- For example:
- At 120 bpm, the cardiac cycle duration is 0.8 seconds.
- At 140 bpm, the duration can be calculated as follows:
\[ \text{Duration} = \frac{60 \text{ seconds}}{\text{Heart Rate in bpm}} = \frac{60}{140} \approx 0.43 \text{ seconds} \]
- At 160 bpm, the duration would be:
\[ \text{Duration} = \frac{60}{160} \approx 0.375 \text{ seconds} \]

5. **Conclusion**: Since the heart rate increases when running, the duration of the cardiac cycle will be less than 0.8 seconds. Therefore, the correct answer is that the duration of the cardiac cycle while running on a treadmill is **less than 0.8 seconds**.