Modelling heart rate training zones

What you are doing

A coach has built a spreadsheet model that turns an athlete’s age into their heart rate training zones. It has mistakes in it. You will work out how the model is built, find and fix the mistakes, use the fixed model to judge five real training sessions, write a rule that names the zone for any heart rate, and decide what the model cannot tell the coach.

Key words: input (data you type in), process (a formula that does something to the data), output (the answer the model gives), bpm (beats per minute).

Step 1: how the model is built

Look at Mari’s spreadsheet on the pack (section 4). Fill in the table for the columns in row 2.

Which column is typed in but never used by any formula?

Step 2: find and fix the errors

Row 2 (Nia) is correct. Compare every other row with row 2, in the formula view and the values view. There are four errors. For each, give the cell, say what is wrong, write the correct formula and the correct value (nearest whole number).

Two of the errors give numbers that look believable. Which two, and why does that make them more dangerous than the others?

Step 3: run the model for two new athletes

Work it out with a calculator, exactly as the correct formulas would. Round to the nearest whole number.

Step 4: use the corrected model

For each session on the pack (section 5), work out the heart rate as a percentage of correct MHR (one decimal place). Name the training zone. Then use the energy systems fact card to name the predominant energy system, with a reason about intensity and duration.

Answer Mari’s note. (a) Was she below the aerobic threshold? (b) Was Priya’s sprint session an aerobic session? Explain both.

Step 5: write a rule that names the zone

Mari wants a new column H where she types the session heart rate, and a column I that names the zone automatically. Write the steps (an algorithm) in plain English or as IF … ELSE IF … rules. It must give one of four outputs: below aerobic threshold, aerobic zone, anaerobic zone, above 90%. Decide what happens at exactly 60%, 80% and 90%.

Test your rule. Sam is 20, so MHR is 200. Fill in what the rule should output, then check your rule gives the same answer. Good tests sit right on and right next to the boundaries.

Step 6: what the model cannot tell the coach

Give two limitations of this model. For each, give evidence from the pack or your answers, and say how Mari could improve the model or how she should use it.

Step by step

1. 5 min: Read the pack with your partner. Highlight the zone percentages and the energy system durations.
2. 6 min: Step 1. Inputs, processes and outputs.
3. 12 min: Step 2. Find all four errors. Compare each row with row 2.
4. 6 min: Step 3. Two new athletes.
5. 12 min: Step 4. Five sessions, then answer Mari’s note.
6. 11 min: Step 5. Write the rule, then test it with all six heart rates.
7. 8 min: Step 6. Two limitations with evidence.

If you finish early

• Some coaches use the heart rate reserve method, which uses column C. Target heart rate = resting HR + (MHR − resting HR) × the percentage. Work out Nia’s 60% and 80% targets this way and compare them with the model’s. Which method gives a harder session?
• Write the rule from Step 5 as one spreadsheet formula using nested IF functions, for cell I2.
• Plan one session for Owain that should keep him in the aerobic zone for 30 minutes. What heart rates should his watch show?