he lactate-power curve test
The lactate-power curve test
The lactate-power curve test (often simply called a lactate threshold test) is a cornerstone assessment in endurance sports like cycling and running. It measures how your blood lactate concentration responds to increasing exercise intensity, allowing you to pinpoint your specific metabolic thresholds and establish highly accurate training zones.
Graded Increments: The athlete exercises on a stationary bike (ergometer) or treadmill. The test starts at a very easy intensity and incrementally increases the power output (Watts) or speed every 3 to 5 minutes.
Blood Sampling: At the end of each step, a tiny drop of blood is taken (usually from the earlobe or fingertip) to measure the concentration of lactate in the blood, expressed in millimoles per liter (mmol/L). Heart rate and perceived exertion are also recorded at each stage.
Plotting the Curve: The collected data is used to plot a graph with Power Output (Watts) on the horizontal X-axis and Blood Lactate (mmol/L) on the vertical Y-axis.
Understanding the Curve and Thresholds
At low intensities, your body clears lactate as quickly as it produces it, keeping blood levels low and stable (the baseline). As intensity rises, you hit two critical turning points on the curve:
LT1 (Aerobic Threshold): The point where blood lactate first begins to rise above the resting baseline (typically around 2.0 mmol/L). Exercise below this point is purely aerobic and can be sustained for hours.
LT2 (Anaerobic Threshold / Lactate Threshold): The point where lactate clearance can no longer keep up with production, causing lactate to accumulate rapidly (often associated with 4.0 mmol/L, known as OBLA - Onset of Blood Lactate Accumulation, though the exact number varies by individual). This is a sharp inflection point on the graph. Pushing past this intensity means fatigue will set in very quickly.