Investigate and state the effect of physical activity on pulse rate.

8.2 Transport in Humans: Pulse Rate & Physical Activity 🏃‍♂️

What is Pulse Rate?

Pulse rate is the number of heartbeats per minute (bpm). It can be felt as a rhythmic thump at places like the wrist or neck. Think of it as a metronome that keeps the rhythm of your body.

• Measured in beats per minute (bpm).
• Resting pulse rate for healthy adults: 60–100 bpm.
• Higher pulse rate means the heart is working harder.

How Physical Activity Affects Pulse Rate

When you run, jump, or play sports, your muscles need more oxygen. The heart responds by pumping faster and stronger. The pulse rate rises to meet the demand, just like a turbo engine revving up.

The relationship can be expressed as:

$$HR = \frac{60}{T}$$

where $T$ is the time between beats in seconds.

After exercise, the pulse rate gradually returns to resting levels. Regular training improves cardiovascular efficiency, so the resting pulse rate often drops.

Key Concepts for the Exam

• Define pulse rate and explain how it is measured.
• Describe the effect of physical activity on pulse rate.
• State the formula for maximum heart rate: $MHR = 220 - \text{age}$.
• Explain heart rate zones and how training shifts them.
• Discuss recovery time and its significance.

Practice Questions

1. A 15‑year‑old athlete has a resting pulse of 55 bpm. What does this suggest about their cardiovascular fitness? Answer: It indicates high fitness because the heart is efficient and needs fewer beats to supply oxygen.
2. Calculate the maximum heart rate for a 20‑year‑old. Answer: $MHR = 220 - 20 = 200$ bpm.
3. Explain why the pulse rate returns to resting levels after exercise.
4. Describe how training can change the heart rate zones for a given individual.

Takeaway

Physical activity increases pulse rate to meet the body's oxygen demand. Over time, regular exercise improves heart efficiency, lowering resting pulse rate and expanding healthy heart rate zones.