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Recovery Process

It is the ability of the body to regain its original state after strenuous exercise or training.

Four process had to be satisfied before the exhausted muscle can perform to its optimum level again. These are-

1. 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 contraction.

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.

OXYGEN DEBT OR EPOC (EXCESS POST EXERCISE OXYGEN CONSUMPTION)

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 exercise.

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 re-establishing the pre-exercise oxygen uptake. The amount of time will depend on the exercise intensity and duration.

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The replenishment of muscle myoglobin with oxygen is normally completed within the time required to recover the Alactacid oxygen debit component.

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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)

• RESTORATION OF 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 exercise.

|Recovery time (S) |Muscle phosphogen stores (ATP and PC) % |

|10 |10 |

|30 |50 |

|60 |75 |

|90 |87 |

|120 |93 |

|150 |97 |

|180 |99 |

|210 |101 |

|240 |102 |

• 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.

• REPLENISHMENT OF MYOGLOBIN STORES

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 GLYCOGEN-

The 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.

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