The correct option is D All of the above
Substrate shortage is one of the causes of metabolic fatigue. Substrates are depleted during exercise, resulting in a lack of intracellular energy sources to fuel contractions. In essence, the muscle stops contracting because it lacks the energy to do so.
If muscle weakness is the result of pain, the person may be able to make muscles work, but it will hurt. Fatigue is a feeling of tiredness or exhaustion or a need to rest because of lack of energy or strength. Fatigue may result from overwork, poor sleep, worry, boredom, or lack of exercise.