|
Once exercise
begins the oxygen uptake does not reach a steady state immediately,
but rather accelerates to meet demands, usually by around the third
minute. The difference between the amount of oxygen actually consumed
and the amount of oxygen that would have been consumed had a steady
state been achieved immediately is termed the oxygen deficit.
A large proportion of the energy at this time is provided by the
shorter-term energy systems.
Regardless of the exercise intensity, oxygen uptake during recovery
always exceeds the resting value (our breathing always takes time
to slow down!). This extra oxygen we need has commonly been termed
the oxygen debt or oxygen recovery period.
The oxygen debt
is calculated as the total oxygen consumed in recovery minus the
total oxygen that would theoretically have been consumed at rest
during the recovery period if the exercise has not been performed.
Within the recovery
process there are two important characteristics of oxygen uptake:
1.
The Fast (Alactic) component of recovery oxygen uptake.
If the exercise period was of short duration (with little temperature
or hormonal disruption) the recovery oxygen uptake follows an exponential
decline (of about 50% of the remaining deficit being repaid each
30 seconds).
Alactic debt
where the high-energy phosphates (ATP and PC) are repaid through
aerobic respiration and the oxygen-depleted haemoglobin in the blood
is reloaded.
2.
The Slow (Lactacid) component of recovery oxygen uptake.
Strenuous exercise increases the body temperature, blood lactate
and hormone levels. Depending on the intensity and duration of the
exercise, the slower phase of recovery may extend the time to needed
to return to pre-exercise oxygen uptake levels. This may take up
to several hours (or even a day).
Lactacid debt
is where the lactic acid is removed from the muscles and blood during
recovery. There are several ways the body removes lactic acid, but
the two main ways are by its oxidation to carbon dioxide and water
by the aerobic system and reconversion to glycogen, which takes
place in the liver.
Excess
Post-exercise Oxygen Consumption (EPOC) - another name for Oxygen
Recovery Process
Causes of EPOC
after heavy exercise:
- Need to resynthesize
ATP and PC
- Need to resynthesize
lactate to glycogen
- Need to restore
oxygen to blood
- Need to reduce
elevated core body temperature
- The effects
of hormones
- The effect
of elevated heart rate, ventilation and tissue repair
|
