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BIOLOGY · Stage 8 · Chapter 5: Respiration and the Respiratory System

Biology 5.7 The effect of exercise on the breathing rate — Alhussan International Academy - Biology (Stages 7-9) Revision Notes & Topical Questions

5 min read 6 parts Lesson 7 of 12

📚 Alhussan International Academy - Biology (Stages 7-9) Hub / Topical Revision
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Biology 5.7 The effect of exercise on the breathing rate — Alhussan International Academy — Biology (Stages 7–9) notes: Explain why breathing rate increases with exercise and plan, carry out and analyse an investigation into it.Factors — age, size, fitness and what you are doing …

  • Typical rates
  • Prediction
  • Sitting quietly
  • Resting between trials
  • Class results
  • Reliability

Section 1 of 6Factors affecting breathing rate

  • Factors
    • age, size, fitness and what you are doing all affect the number of breaths per minute.
  • Typical rates
    • about 12 to 20 breaths per minute at rest, rising to 40 or more in intense exercise.
  • Prediction
    • breathing rate should increase after exercise, based on the scientific knowledge that muscles need more energy from respiration.

Section 2 of 6Why exercise increases breathing rate

  • Energy
    • contracting muscles need more energy, from respiration using glucose and oxygen and releasing carbon dioxide.
  • Gases
    • faster respiration uses more oxygen and produces more carbon dioxide in muscle cells.
  • Detection
    • carbon dioxide dissolves in blood and makes it slightly acidic, and sensors in the brain detect the higher carbon dioxide level.
  • Response
    • the brain signals the diaphragm and intercostal muscles to contract faster and more strongly, so breathing rate and depth of each breath increase.
  • Heart
    • heart rate rises too, so blood carries oxygen to the muscles and removes carbon dioxide faster.

Section 3 of 6Investigating the resting breathing rate

  1. Each student sits still, without speaking, for 1 minute.
  2. Using a stopwatch, each records the number of breaths in one minute, counting breathing in and out again as one breath.
  3. Repeat twice more.
  4. Calculate the mean resting breathing rate per minute (the sum of the three readings divided by 3).
  • Sitting quietly
    • movement or speaking would raise breathing rate and give a false baseline.

Section 4 of 6Investigating the effect of exercise

  1. Each student runs on the spot for 1 minute.
  2. As soon as the exercise stops, each starts the stopwatch and counts the breaths in one minute.
  3. Sit quietly until the breathing rate returns to its resting level, then repeat twice more.
  4. Calculate the mean breathing rate after exercise to the nearest whole breath.
  • Resting between trials
    • it returns the breathing rate to normal so every trial starts from the same condition.
  • Variables
    • the independent variable is the exercise, the dependent variable is breathing rate,
      • and controls are the same people, room, rest time and counting method.
      • (type or duration)

Section 5 of 6Analysing the results

  • Class results
    • the mean resting and after-exercise rates for each student go in a table, and a bar graph shows the effect of exercise.
  • Pattern
    • breathing rate is higher after exercise, and rises further with more intense exercise.
  • Recovery
    • the rate stays high for a few minutes after stopping, because the body repays the oxygen debt and clears carbon dioxide.
  • Fitness
    • fitter people have lower resting rates and recover faster,
    • because their lungs and heart are more efficient and their muscles have more capillaries and mitochondria.
  • Reliability
    • several readings and a mean reduce random error and anomalous results,
      • and whole-class data are more useful because individual differences average out and anomalies stand out.

Section 6 of 6Limitations and improvements

  • Limitations
    • counting breaths is subjective, people may breathe differently when watched, and different people exercise at different intensities.
  • Improvements
    • use a sensor and data logger or a second person to count, use several test subjects and rest completely between trials.
  • Safety
    • anyone with asthma or a heart condition may opt out, stop if someone feels unwell and make sure the exercise suits the group.

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