Keep this light. Ask every pupil to find their own pulse for about ten seconds. If some cannot find it, help them on the side of the neck (carotid) or the wrist (radial). Do not start measuring yet.

Key question: What do you think happens to your heart and lungs when you run or jump?

Before the lesson: push desks back so pairs have floor space for the one-minute activity; print the Investigation Journal page; open the fair-test-timer and data-recorder on the IWB.

Misconception to head off: some pupils think the heart and lungs work separately. Stress that they are one oxygen-delivery team: lungs fill the blood with oxygen, the heart delivers it.

Nature of STEM: biologists and doctors measure pulse and breathing to find out how the body keeps us healthy. Today we work the same way: we ask a question we can test with numbers.

This is the first time the class turns an "I wonder" into a testable question. Keep the theme teacher-set (exercise and the body) but give pairs a real design choice of activity. Model the shape out loud: I wonder if exercise changes our pulse and breathing. So we will measure both before and after the same one-minute activity, in beats and breaths per minute.

Offer three safe options only: steady step-ups on a low step or PE bench, high-knee marches on the spot, or star jumps. Pairs write the activity name into the question stem so the question is theirs.

Pin the unit once: every count is for a full 15 seconds, then multiply by 4 to get the rate per minute. Every number pupils write, and every column on the data-recorder, uses per minute, never a raw 15-second count under a per-minute label.

Predictions are never wrong. Accept both "both will go up" and more cautious ideas. Ask a few pairs to share their activity choice and why.

Worked example to model (say aloud before groups measure):

• I wonder whether a short burst of exercise changes my pulse and breathing.
• I choose one minute of high-knee marches.
• I predict both will go up, because my muscles will need more oxygen.
• I test by counting pulse and breaths for 15 seconds at rest (×4), doing one minute of the activity, then counting both again twice and averaging.
• I observed (example numbers for you; do not write these on the board before pupils measure): resting pulse about 76 per minute, after about 112; resting breaths about 16 per minute, after about 28.
• I think the heart and lungs sped up together to deliver more oxygen.

Before you demonstrate

Open the fair-test-timer on the IWB in stopwatch mode. Practise finding a pulse on a volunteer (or yourself) so the class sees finger placement.

Model the method

1. Sit still for 30 seconds.
2. Start the timer. Count pulse beats for exactly 15 seconds. Stop. Multiply by 4. That is beats per minute. Write it down.
3. Do a second 15-second pulse count. Multiply by 4. Average the two per-minute numbers: add them and divide by 2.
4. Repeat the same pattern for breaths (chest rises once = one breath).

What "average" means here: two readings, add them, divide by 2. Never say "the middle of two" — that phrase does not make sense for two numbers.

Common pitfalls: counting for roughly 15 seconds instead of exactly; forgetting to multiply by 4; writing the raw 15-second count as if it were per minute; pressing too hard on the neck.

Pupils who should not do the one-minute activity become timers and recorders for their pair — still full scientists in the investigation.

Runnable pairing protocol (one shared activity round)

There is one whole-class one-minute round on the IWB timer. During that minute every pupil who can exercise does their pair's chosen activity at the same time. Partners do not take turns doing two full rest–activity–remeasure cycles; that will not fit the slot.

• Resting measures: both partners sit and each measures their own pulse and breathing (partner helps with the 15-second timing and the ×4). Do the 15-second counts together using the board timer so the class stays in step.
• Activity: start the fair-test-timer for one minute. All movers begin together. Non-movers stand clear and watch the timer for their partner.
• After measures: stop together. Each mover immediately measures their own after-exercise pulse (twice) and breathing (twice), again with partner support on timing. Work quickly so the after readings still show the rise.

If only one pupil in a pair can exercise, that pupil is the only data subject; the other is timer and recorder throughout and still counts as a full scientist.

Setup

Pairs spread out. Step-ups: low step or bottom of a PE bench. High-knee marches or star jumps: clear floor space. Keep the pace steady, not a race. Different pairs may use different activities; the fair factor is the shared one-minute duration on the class timer.

During the investigation

• Drive the fair-test-timer on the IWB for the shared one-minute activity so the whole class starts and stops together.
• Pairs may use their own watches or the board timer for the 15-second counts.
• Circulate: check finger placement, remind them to multiply by 4, and check that both pulse and breathing are recorded for the person being measured.

What to expect: resting pulse often sits roughly 70–100 beats per minute for this age; after the activity it commonly rises. Breathing rate also rises. Exact numbers vary — that is fine. The pattern (both go up) is the learning.

If a reading looks impossible (e.g. 20 or 200 beats per minute), ask the pair to re-count once calmly. Do not shame the first attempt.

Safety in the moment: anyone dizzy or uncomfortable sits out the activity and keeps the timer role. No competition for fastest moves.