Define Lactate threshold.

• A. The onset of muscle fatigue
• B. The maximum lactate threshold
• C. The point at which blood lactic acid rises exponentially during incremental exercise
• D. The resting lactate level

Answer: (C)

Lactate threshold is the exercise intensity at which blood lactate begins to accumulate rapidly, due to lactate production surpassing clearance. At lower intensities, lactate produced is cleared efficiently, so blood lactate stays near baseline. As intensity increases toward this threshold, clearance can’t keep up with production, leading to an exponential rise in blood lactate during incremental exercise. This point marks a shift toward greater reliance on anaerobic glycolysis and is a key marker for endurance training zones. Resting lactate levels stay low and aren’t indicative of where this rapid rise begins, and the term isn’t used for a maximum value or a general onset of fatigue.