5.7Chapter 5: Respiration and the Respiratory System

The effect of exercise on the breathing rate — Alhussan Biology - Stage 8 Revision Notes & Topical Questions

5 min read 8 parts Lesson 7 of 12 2 quizzes

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Lesson summary

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 8Factors affecting breathing rate

Factors

Factors age, size, fitness and what you are doing all affect the number of breaths per minute.

Typical rates

Typical rates about 12 to 20 breaths per minute at rest, rising to 40 or more in intense exercise.

Prediction

Prediction breathing rate should increase after exercise, based on the scientific knowledge that muscles need more energy from respiration.

Section 2 of 8Why exercise increases breathing rate

Energy

Energy contracting muscles need more energy, from respiration using glucose and oxygen and releasing carbon dioxide.

Gases

Gases faster respiration uses more oxygen and produces more carbon dioxide in muscle cells.

Detection

Detection carbon dioxide dissolves in blood and makes it slightly acidic, and sensors in the brain detect the higher carbon dioxide level.

Response

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 heart rate rises too, so blood carries oxygen to the muscles and removes carbon dioxide faster.

Section 3 of 8Investigating the resting breathing rate

Each student sits still, without speaking, for 1 minute.

Using a stopwatch, each records the number of breaths in one minute, counting breathing in and out again as one breath.

Repeat twice more.

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 8Investigating the effect of exercise

Each student runs on the spot for 1 minute.

As soon as the exercise stops, each starts the stopwatch and counts the breaths in one minute.

Sit quietly until the breathing rate returns to its resting level, then repeat twice more.

Calculate the mean breathing rate after exercise to the nearest whole breath.

Resting between trials

Resting between trials it returns the breathing rate to normal so every trial starts from the same condition.

Variables

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 8Analysing the results

Class 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

Pattern breathing rate is higher after exercise, and rises further with more intense exercise.

Recovery

Recovery the rate stays high for a few minutes after stopping, because the body repays the oxygen debt and clears carbon dioxide.

Fitness

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

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 8Limitations and improvements

Limitations

Limitations counting breaths is subjective, people may breathe differently when watched, and different people exercise at different intensities.

Improvements

Improvements use a sensor and data logger or a second person to count, use several test subjects and rest completely between trials.

Safety

Safety anyone with asthma or a heart condition may opt out, stop if someone feels unwell and make sure the exercise suits the group.

Section 7 of 8Key terms

Term	Meaning
Breathing rate	The number of breaths per minute.
Tidal volume	The volume of air in one breath.
Heart rate	The number of heartbeats per minute.
Oxygen debt	The extra oxygen needed after exercise.
Fitness	The ability of the body to carry out exercise efficiently.
Mean	The average of a set of values.