Question

The sensation of fatigue in the muscle after prolonged strenuous physical work is caused by
A. A decrease in the supply of oxygen
B. The depletion of glucose
C. The accumulation of lactic acid
D. All of the above

Answer 1

Hint: In muscle fibres due to less oxygen supply, lactic acid is produced because of anaerobic respiration. Also due to the less amount of glycogen in muscles, less glucose is provided for respiration. This causes muscle fatigue.

Complete answer: Muscles which have less myoglobin and mitochondria.
1. Myoglobin is a pigment found in muscles and it is responsible for binding oxygen and providing it during respiration. Mitochondria are responsible for producing energy using glucose and oxygen, called respiration. Energy is produced in form of ATP. This is required for muscle contraction.
2. If oxygen is not supplied in the proper amount ATP is produced by anaerobic respiration.
3. In aerobic respiration, glucose is oxidized and lactic acid is also made.
4. During prolonged physical work, this acid is produced more and it accumulates in muscles because of this tiredness feel, called muscle fatigue.
5. These types of muscles are called white muscle fibers that have fewer mitochondria, myoglobin, and less stored glycogen. Ex. Eyeballs and muscles of feet.

So, the correct answer is “Option D”.

Note: Unlike white muscle red muscles, have a high amount of glycogen, more mitochondria, and myoglobin. So, these muscles do not feel fatigued.
Ex. Muscles of back.