Getting Started with Heart Rate Calculations

In PE, data isn't just about scores on a leaderboard. It’s about understanding how your body is working! One of the most important pieces of data we use is your heart rate. By calculating your heart rate zones, you can figure out if you are training hard enough to improve your fitness, or if you are pushing your body into a different type of energy production.

Don't worry if you find math a bit "scary"—the formulas we use in Edexcel GCSE PE are straightforward, and you are allowed to use a calculator in your exam!

Note: This chapter focuses on the math behind these zones. To learn more about how to present this data in charts, see the chapter on "Presenting data in tables and graphs."

Step 1: Finding Your Maximum Heart Rate (MaxHR)

Before you can find your training zones, you need to know the fastest your heart can safely beat in one minute. This is called your Maximum Heart Rate (or MaxHR for short).

As we get older, our maximum heart rate naturally drops. To find yours, we use the simplified Karvonen formula:

\(220 - \text{age} = \text{MaxHR}\)

Example: If you are \(15\) years old, your calculation would look like this:
\(220 - 15 = 205\) beats per minute (bpm)

Key Takeaway: Always start by subtracting the person's age from \(220\). This is the "ceiling" for their heart rate.

Step 2: The Aerobic Training Zone (\(60\%\) to \(80\%\))

The Aerobic Training Zone is where you train to improve your cardiovascular fitness (aerobic endurance). This is "steady-state" exercise, like jogging or long-distance swimming, where your heart and lungs can keep up with the oxygen demand.

To train in this zone, your heart rate must be between \(60\%\) and \(80\%\) of your MaxHR.

How to calculate it (for a \(15\)-year-old with a MaxHR of \(205\)):
1. Find the bottom of the zone (\(60\%\)): \(205 \times 0.60 = 123 \text{ bpm}\)
2. Find the top of the zone (\(80\%\)): \(205 \times 0.80 = 164 \text{ bpm}\)

So, a \(15\)-year-old needs their heart rate to stay between \(123 \text{ bpm}\) and \(164 \text{ bpm}\) to be in the aerobic zone.

Did you know?

The word "aerobic" means "with oxygen." When you are in this zone, your body is using oxygen to help turn fats and carbohydrates into energy!

Step 3: The Anaerobic Training Zone (\(80\%\) to \(90\%\))

The Anaerobic Training Zone is for high-intensity work, like sprinting or heavy weightlifting. This is where you are working so hard that your body cannot supply oxygen fast enough, leading to the production of lactic acid.

To train in this zone, your heart rate must be between \(80\%\) and \(90\%\) of your MaxHR.

How to calculate it (for a \(15\)-year-old with a MaxHR of \(205\)):
1. Find the bottom of the zone (\(80\%\)): \(205 \times 0.80 = 164 \text{ bpm}\)
2. Find the top of the zone (\(90\%\)): \(205 \times 0.90 = 184.5 \text{ bpm}\) (you can round this to \(185 \text{ bpm}\))

If that student's heart rate goes above \(164 \text{ bpm}\), they have moved from aerobic training into anaerobic training.

Quick Review:
- Aerobic Zone: \(60\% - 80\%\) of MaxHR. Focuses on endurance.
- Anaerobic Zone: \(80\% - 90\%\) of MaxHR. Focuses on power and speed.

Common Mistakes to Avoid

1. Mixing up the percentages: Remember that Anaerobic is higher intensity, so it uses the higher numbers (\(80-90\%\)). Aerobic is lower intensity (\(60-80\%\)).

2. Forgetting to subtract the age: If a question gives you an athlete's age, use it! Don't just use \(220\) as the MaxHR for everyone.

3. Decimal points: In the exam, if you get a result like \(164.8\), it is usually safest to round to the nearest whole number (\(165\)), as heart beats are measured in whole numbers.

Step-by-Step Guide for Exam Questions

If you see a question asking you to calculate a training zone for an athlete, follow these three steps:

Step A: Find the MaxHR (\(220 - \text{age}\)).
Step B: Identify the zone requested (Aerobic = \(60-80\%\) or Anaerobic = \(80-90\%\)).
Step C: Multiply the MaxHR by the percentage decimals (e.g., \(\times 0.60\), \(\times 0.80\), or \(\times 0.90\)).

Summary Checklist

- MaxHR Formula: \(220 - \text{age}\)
- Aerobic Threshold: \(60\%\) of MaxHR
- Anaerobic Threshold: \(80\%\) of MaxHR
- Anaerobic Ceiling: \(90\%\) of MaxHR

Key Takeaway: These calculations are part of the Principles of Training (specifically Intensity). By using these numbers, a performer can ensure they are training at the correct level to see the long-term effects of exercise, such as a stronger heart (hypertrophy) or increased capillarisation.