Final answer:
Glucose is the preferred fuel of muscles because it can be metabolized under anaerobic conditions, which is particularly important during high-intensity activities when the demand for ATP is immediate and oxygen supply may be limited. The answer is option C.
Step-by-step explanation:
Glucose is the preferred fuel of muscles because it can be metabolized under anaerobic conditions. This means that glucose can be broken down to provide energy in the form of ATP when oxygen is scarce or when a rapid energy demand outpaces the oxygen supply, such as during high-intensity activities like sprinting. By contrast, fatty acids are the primary energy source during sustained low-intensity activities where aerobic metabolism is predominant. It's important to note that protein can also be used as fuel, but to a lesser extent, particularly during long endurance exercises or when dietary energy intake is insufficient.
During periods of increased exertion, muscle glycogen is converted to glucose which undergoes glycolysis and can continue into the Krebs cycle if oxygen is present. As exercise continues at low to moderate intensity, fatty acid metabolism increases. As muscle glycogen stores become depleted, fatigue sets in, highlighting the body's reliance on glucose as a rapid and accessible energy source.
Metabolism during physical exercise is complex. Carbohydrates, broken down to glucose, provide energy through metabolic pathways, and the role of glucose is crucial in both anaerobic and aerobic processes within the muscles.