Explain the main cause of muscle fatigue during this race.

Explain the main cause of muscle fatigue during this race.

• A. Lactate accumulation and increased acidity
• B. Dehydration
• C. Inhibition of enzyme action
• D. Lack of oxygen

Answer: (A)

When a race is intense, the muscles push energy production beyond what oxygen alone can supply, so they rely on anaerobic glycolysis. This process converts glucose to lactate, regenerating NAD+ so glycolysis can continue, but it also releases hydrogen ions. The buildup of these H+ ions lowers the muscle’s pH, creating an acidic environment that interferes with the proteins involved in contraction and slows enzyme reactions needed for energy release. This combination directly reduces force and accelerates fatigue, making lactate accumulation and increased acidity the most immediate cause of fatigue in this scenario. Dehydration, lack of oxygen, or enzyme inhibition can contribute, but they’re not the primary mechanism driving fatigue here; the acid buildup from lactate production is what most strongly limits performance.

When a race is intense, the muscles push energy production beyond what oxygen alone can supply, so they rely on anaerobic glycolysis. This process converts glucose to lactate, regenerating NAD+ so glycolysis can continue, but it also releases hydrogen ions. The buildup of these H+ ions lowers the muscle’s pH, creating an acidic environment that interferes with the proteins involved in contraction and slows enzyme reactions needed for energy release. This combination directly reduces force and accelerates fatigue, making lactate accumulation and increased acidity the most immediate cause of fatigue in this scenario. Dehydration, lack of oxygen, or enzyme inhibition can contribute, but they’re not the primary mechanism driving fatigue here; the acid buildup from lactate production is what most strongly limits performance.