A track sprinter has just completed a 200 m sprint. His legs are \"burning\"as l
ID: 3480763 • Letter: A
Question
A track sprinter has just completed a 200 m sprint. His legs are "burning"as lactic acid builds up within his muscle cells. This lactic acid is produced as his muscle cells increase the rate of glycolysis and fermentation in order to provide the necessary ATP to power the quick muscular contractions necessary during sprinting. The production of excess lactic acid in skeletal muscle cells leads to local acidosis of the tissues. What effect does local acidosis have on the delivery of oxygen to the working tissues? What is this effect called? Why is it important in this situation?Explanation / Answer
Lactic acid is synthesized during anaerobic metabolism ie during strenous exercise. Accumulation of lactic acid leads to lactic acidosis. The level of oxygen is greatly reduced and this is compensated by increasing the CO2 Exhalation for a short time. Rapid breathing will be initiated due to arterial hyperventilation and this will shift the synthesis of lactic acid. The blood pH will be normalized.
Lactic acidosis is of 2 types
Type A - Decreased blood flow and oxygenation
Type B - Disease or metabolic error
Lactic acidosis may be due to 2 reasons
Hypoxemia : In this condition, PaO2 < 36 mmHg. That is, the partial pressure in arteries is very low. It is this partial pressure that decides the flow of oxygen from arteries to the tissues. It flows from high PaO2 to low. So in this condition, there is a decrease in the oxygen diffusion from blood to tissues.
Hypoperfusion : it is the condition in which there is inadequate delivery of oxygen from blood to tissues.
If lactate is not synthesized, muscle fatigue will occur quickly and exercise cannot be continued effectively. It is because lactate induces glycolysis and the low pH condition will be reversed quickly.
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