Heart Rate & Recovery: Training for the Detroit Marathon
Measure how the circulatory and respiratory systems respond to exercise and how they recover.
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Class period:
Date:
Standards
HS-LS1-3 — Plan and conduct an investigation to provide evidence that feedback mechanisms maintain homeostasis.
MS-LS1-3 — Construct an argument supported by evidence that the body is a system of interacting subsystems.
Why Does This Matter?
Every October thousands of runners take part in the Detroit Free Press Marathon, one of the few marathons that crosses the U.S.–Canada border. Race-day performance depends on how quickly the heart, lungs, and muscles can respond to demand — and how well they recover. You will measure the same responses on a classroom scale.
Objective
Measure resting heart rate, exercise heart rate, breathing rate, and heart-rate recovery, then explain the results using feedback mechanisms and body-system interactions.
Materials
- Stopwatch or classroom timer (one per pair)
- A sturdy step or bottom stair about 20–30 cm high (or space to march in place)
- Pencil and graph paper
- Water and a place to sit down
Safety & consent: Participation is voluntary. Students with asthma, a heart or other medical condition, an injury, or a doctor's activity restriction may act as timer and recorder instead. Keep the exercise moderate — stop immediately if you feel dizzy, short of breath, or in pain. Never exercise to exhaustion in class.
Procedure
- Resting measures: Sit quietly for 3 minutes. Your partner counts your pulse at the wrist for 30 seconds (multiply by 2) and counts your breaths for 30 seconds (multiply by 2).
- Exercise: Step up and down on the step at a steady pace of one full step every 2 seconds (30 steps per minute) for 3 minutes, or march in place at the same pace.
- Immediately after: Sit down. Measure pulse and breathing rate right away (use a 15-second count × 4).
- Recovery: Measure pulse (15 seconds × 4) at 1, 2, 3, and 4 minutes after stopping.
- Swap roles with your partner and repeat.
- Graph heart rate (y-axis) against time (x-axis) from rest through the end of recovery.
Data Table
| Measure | Rest | End of exercise | 1 min | 2 min | 3 min | 4 min |
|---|---|---|---|---|---|---|
| Heart rate (beats/min) | ||||||
| Breathing rate (breaths/min) |
Analysis Questions
- Describe how heart rate and breathing rate changed during exercise. Explain why, using the terms oxygen, carbon dioxide, and cellular respiration.
- Draw and label a negative feedback loop for body temperature during exercise (stimulus, receptor, control center, effector, response).
- Calculate your heart-rate drop in the first minute of recovery (end-of-exercise rate minus 1-minute rate). What might a faster drop indicate, and what factors could change it?
- How might a hot, humid race day or poor air quality change these measurements for a runner? Explain which body systems are involved.