At lactate threshold, which statement describes lactate production vs clearance?

• A. Production equals clearance.
• B. Production exceeds clearance.
• C. Clearance exceeds production.
• D. No lactate production.

Answer: (B)

The main idea here is the balance between how much lactate is produced and how quickly it’s cleared from the blood. As exercise intensity increases, glycolysis speeds up and more pyruvate is converted to lactate to keep glycolysis going and to regenerate NAD+. This raises lactate production. Lactate is removed mainly by oxidation in working muscles, the heart, and brain, and by making glucose in the liver. These clearance pathways can handle only up to a point. At lactate threshold, the production rate outstrips the clearance rate, so lactate starts to accumulate in the blood, which is why you see a sharp rise in lactate concentration.

So, the statement that production exceeds clearance is the best description. If production and clearance were equal, lactate would plateau; if clearance exceeded production, lactate would not accumulate; and lactate is produced at the threshold, so saying there is no lactate production isn’t correct.