How the body changes
4.The lungs start
1. First, the muscles breathing faster and
start to work harder more deeply. They
remove CO2 faster and
2.This means more take in oxygen faster
carbon dioxide 5. At the same time
forms. The level the heart starts beating
rises in your blood faster, pumping blood
faster around the body.
3. The brain detects
this rise. It sends 6.Since the heart and
signals to your heart lungs are both working
and lungs to work harder, more oxygen
faster reaches the muscles
each minute, and
7. This means the muscle can more carbon dioxide is
keep on working carried away
Other Changes to the body
Increased respiration in your muscles generate more
heat. So your blood gets hotter
To cool the blood down, more is shunted close to the
skin. This makes you redden.
You also sweat, which cools you by evaporation.
Tidal volume All these increase
Fit and less fit during
Two runners run the same course one is fitter than the other.
You can tell by looking at their heart rate
82 Runner A
65 Runner B
0 5 10 15 20 25
(i) Lower resting heart rate (ii) Lower heart rate throughout (iii) Quicker to 5
recover back to resting rate
Lactic acid removal
Oxygen removes lactic acid from the body.
This is called repaying the oxygen debt. The
process is faster when you do a cool down
Lactic Resting recovery
0 1 2
Recovery after exercise
Muscles may suffer minor damage during training.
Your body has to repair this.
Stiffness and soreness take time to clear.
Stretching as part of a cool down helps prevent
Glycogen stores need to be replaced
It can take up to 48 hours for glycogen stores to
How long does recovery
It depends on
How strenuous the exercise is
Your fitness. The fitter you are the faster you
Allow 24-48 hrs between training sessions to
If you train every day, follow a heavy session
one day with a light session the next