Transcript Effects of exercise - King`s General Science

Effects of exercise
IGCSE Biology
What’s happening in your muscles?
In normal conditions our body uses oxygen to fully break down glucose in
aerobic respiration:
2900 kJ
Glucose + oxygen  energy + water + carbon dioxide
During hard exercise, muscles use
up a lot of glucose to get enough
energy.
Sometimes not enough oxygen can
get to the muscles so anaerobic
respiration (without oxygen) takes
place and Lactic acid forms.
Why does this happen?
During vigorous exercise you need a lot more energy and get it by:
 Breathing deeper and faster
 Dilated blood vessels deliver more oxygen to muscles (and increased heart
rate)
 When at maximum, body starts to respire anaerobically (making lactic acid),
but
Muscle fatigue results from a lack of
oxygen and a build up of lactic acid.
Investigating exercise’s effects on pulse rate
Pupil Activity
Copy this table into your notes:
Beats per min
Sitting down
Straight after exercise
2 min after exercise
1.
Measure your resting pulse rate over 1 minute.
2.
Exercise for 2 minutes.
3.
Measure pulse rate again.
4.
Wait for 2 mins.
5.
Measure pulserate again.
6.
How has the pulse rate been affected by exercise?
7.
Why does your body do this in response to exercise?
Anaerobic respiration
Instead of glucose forming CO2 and H2O, it is broken down without oxygen
into an intermediate, lactic acid, giving less energy:
120 kJ
Glucose  Lactic acid + energy
BUT lactic acid accumulates in the muscles causing muscle fatigue and
cramps.
To avoid damage to cells it has to be broken down
fully to CO2 and H2O immediately after the exercise
has finished. This needs more oxygen (oxygen
debt)…
Oxygen debt
In order to get the extra oxygen to 'pay back' the debt, the body continues
to breathe deeply for some time after vigorous activity has ceased.
When all the lactic acid in the muscles is broken down the oxygen
debt has been repaid and normal aerobic respiration resumes.
Recovery time is the time taken to return to normal levels of pulse rate,
breathing rate and lactic acid.
It can be used as an indication of physical fitness because a fit person
will recover faster than an unfit person- their breathing and pulse will return
to normal in a shorter time.
How does training help?
With exercise the pulse rate, breathing rate and lactic acid level
rise less in an athlete than in an untrained person
because training and fitness makes aerobic
respiration more efficient by:
improving the efficiency of the lungs
and circulation.
This means less of an oxygen debt is built up
during exercise.
Hence, less extra oxygen is needed
afterwards to break down the lactic acid.
Recovery time
Recovery time is the time taken to return to normal levels of pulse rate,
breathing rate and lactic acid.
It can be used as an indication of physical fitness because a fit person
will recover faster than an unfit person- their breathing and pulse will return
to normal in a shorter time.
Only elite athletes
reach top 3
 Heart volume
Training summary
 Volume blood
pumped
Explain the relationship between the effects of
training & recovery time.
 Resting pulse
rate
Fitter person has faster recovery because:
 Lung volume
Improved
circulation to
muscles
 Volume oxygen per
breath
 Breathing rate