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Recovery Process
It is the ability of the body to regain its original state after strenuous exercise or
Four process had to be satisfied before the exhausted muscle can perform to its
optimum level again. These are1. Restoration of muscle phosphogen stores
2. Removal of lactic acid from the muscles and blood
3. Replenishment of myoglobin stores with oxygen
4. Replenishment of muscle glycogen
During muscular exercise, blood vessels in muscles dilate and blood flow is increased
in order to increase the available oxygen supply. Up to a point, the available oxygen is
sufficient to meet the energy needs of the body. However, when muscular exertion is
very great, oxygen cannot be supplied to muscle fibers fast enough, and the aerobic
breakdown of pyruvic acid cannot produce all the ATP required for further muscle
During such periods, additional ATP is generated by anaerobic glycolysis. In the
process, most of the pyruvic acid produced is converted to lactic acid. Although about
80% of the lactic acid diffuses from the skeletal muscles and is transported to the liver
for conversion back to glucose or glycogen.
Ultimately, once adequate oxygen is available, lactic acid must be catabolized
completely into carbon dioxide and water. After exercise has stopped, extra oxygen is
required to metabolize lactic acid; to replenish ATP, phosphocreatine, and glycogen;
and to pay back any oxygen that has been borrowed from hemoglobin, myoglobin (an
iron-containing substance similar to hemoglobin that is found in muscle fibers), air in
the lungs, and body fluids.
The additional oxygen that must be taken into the body after vigorous exercise to
restore all systems to their normal states is called oxygen debt (A. V. Hill 1886-1977).
This is the excess oxygen consumed following exercise which is needed to replace
ATP which has been used up and to remove lactic acid created during the previous
Eventually, muscle glycogen must also be restored. This is accomplished through diet
and may take several days, depending on the intensity of exercise. The maximum rate
of oxygen consumption during the aerobic catabolism of pyruvic acid is called
"maximal oxygen uptake". It is determined by sex (higher in males), age (highest at
about age 20) and size (increases with body size).
Highly trained athletes can have maximal oxygen uptakes that are twice that of
average people, probably owing to a combination of genetics and training. As a result,
they are capable of greater muscular activity without increasing their lactic acid
production, and their oxygen debts are less. It is for these reasons that they do not
become short of breath as readily as untrained individuals.
The need for oxygen to replenish ATP and remove lactic acid is referred to as the
"Oxygen Debit" or "Excess Post-exercise Oxygen Consumption" (EPOC) - the total
oxygen consumed after exercise in excess of a pre-exercise baseline level.
In low intensity, primarily aerobic exercise, about one half of the total EPOC takes
place within 30 seconds of stopping the exercise and complete recovery can be
achieved within several minutes (oxygen uptake returns to the pre-exercise level).
Recovery from more strenuous exercise, which is often accompanied by increase in
blood lactate and body temperature, may require 24 hours or more before reestablishing the pre-exercise oxygen uptake. The amount of time will depend on the
exercise intensity and duration.
The replenishment of muscle myoglobin with oxygen is normally completed within
the time required to recover the Alactacid oxygen debit component.
The replenishment of muscle and liver glycogen stores depends on the type of
exercise: short distance, high intensity exercise (e.g. 800 metres) may take up to 2 or 3
hours and long endurance activities (e.g. marathon) may take several days.
Replenishment of glycogen stores is most rapid during the first few hours following
training and then can take several days to complete. Complete restoration of glycogen
stores is accelerated with a high carbohydrate diet.
The two major components of oxygen recovery are:
 Alactacid oxygen debt (fast component)- The portion of oxygen required to
synthesise and restore muscle phosphagen stores (ATP and PC). This is the
amount of oxygen required to synthesise and restore muscle phosphogen stores
(ATP and PC)
Alacacid oxygen debt (without LA) represents that portion of oxygen used to
synthesis and restore muscle phosphogen stores (ATP and PC) which have been
almost completely exhausted during high intensity exercise. During the first three
minutes of recovery, EPOC restores almost 99 % of the ATP and CP used during
Recovery time (S)
Muscle phosphogen stores (ATP and
PC) %
 Lactacid oxygen debt (slow component) - The portion of oxygen required to
remove lactic acid from the muscle cells and blood. The slow components of
EPOC is concerned with the removal of LA from the muscles and blood. This can
take several hours, depending on the intensity of the activity and whether the
athlete was active or passive during the recovery phase (continuous activity can
significantly speed up the recovery). Around half of LA is removed after 15
minutes , and most is removed after an hour. Lactacid recovery converts most of
the LA to pyruvic acid which is oxidised via the krebs cycle to create ATP. Once
exercise is over, the liver produce LA into glycogen.
Myoglobin is an oxygen storage protein found in muscles, like Hb. It form a loose
combination with oxygen while the oxygen supply is plentiful, and stores it until the
demand for oxygen increases. Consequently ,muscle has its own built in oxygen
supply. However during exercise the oxygen from myoglobin is quickly used up.
After exercise additional oxygen is required to pay back any oxygen that has been
borrowed from myoglobin stores.
 REPLENISHMENT OF MUSCLE GLYCOGENThe replenishment of muscle and liver glycogen stores depend on the type of exercise.
Short distance, high intensity exercise may take two or three hours, whereas long
endurance activities such as marathon may take several days. Replenishment of
glycogen stores is most rapid during the first few hours after training. Complete
restoration of glycogen stores is accelerated with a high carbohydrate diet.