Cycling Lactate Testing: Applying Blood Lactate Concentration in Training Zone Setting

Introduction

Among all exercise physiology tests, blood lactate testing is considered one of the most precise methods for setting individualized training zones. Lactate is a byproduct of anaerobic glucose breakdown. During low-intensity exercise, lactate production and clearance remain balanced; as intensity increases, lactate begins to accumulate, revealing two key “inflection points”: the lactate threshold (LT1) and the maximal lactate steady state (LT2 / MLSS). These two points correspond directly to the boundaries between aerobic and anaerobic training and serve as the physiological basis for establishing training zones.

The Physiological Significance of Blood Lactate

The Three Segments of the Lactate Curve

The relationship between blood lactate concentration (mmol/L) and exercise intensity forms a characteristic J-shaped curve:

The Difference Between LT1 and LT2

LT1 (First Lactate Threshold): The point where lactate begins to rise above resting levels and deviate from baseline, typically corresponding to a blood lactate concentration of approximately 1.5–2.0 mmol/L. Below LT1 is the “easy” zone, where the body relies primarily on aerobic metabolism and prolonged efforts are sustainable without issue. This intensity corresponds to Zone 2 (aerobic endurance) in most training systems.

LT2 (Second Lactate Threshold) / MLSS (Maximal Lactate Steady State): The highest intensity at which lactate can be maintained at a steady state, generally corresponding to a blood lactate concentration of 3.5–4.5 mmol/L. Beyond LT2, lactate begins to accumulate rapidly and cannot be sustained for extended periods. In terms of power, LT2 closely corresponds to FTP, with one-hour maximal power typically falling near LT2.

The Practical Blood Lactate Testing Protocol

Testing Steps

1. Preparation: Avoid high-intensity training for 24 hours before the test, fast for 2–3 hours, and prepare a lactate analyzer (e.g., Lactate Plus, Edge)
2. Warm-up: 5–10 minutes of low-intensity pedaling
3. Progressive load: Ride 4–5 minutes per stage, with blood sampling at the end of each stage (usually from the earlobe or fingertip), increasing power by 25–40 W per stage
4. Blood analysis: Read blood lactate concentration (mmol/L) immediately
5. Continue until exhaustion or lactate exceeds 8 mmol/L
6. Plot the lactate curve: Use power on the x-axis and lactate on the y-axis to identify the inflection points of LT1 and LT2

Testing Cost Considerations

How to Set Training Zones from Lactate Data

Step 1: Identify the power corresponding to LT1 and LT2

Assume the test results are as follows:

• Power at LT1: 180 W (lactate 2.0 mmol/L)
• Power at LT2: 265 W (lactate 4.2 mmol/L)

Step 2: Define training zones using LT1 and LT2 as boundaries

Differences Between Lactate Testing and FTP Testing

• Accuracy: Lactate testing directly measures physiological response; FTP testing is an indirect estimate
• Cost: FTP testing is nearly free (requires only a power meter); lactate testing is more expensive
• Repeatability: FTP can be self-tested every 6–8 weeks; lactate testing is recommended every 3–6 months
• Zone basis: Lactate testing can distinguish LT1 from LT2, making the boundaries of Zone 2 and Zone 4 clearer; FTP can only determine the Zone 4/5 boundary

Practical Recommendations

1. LT1 is the golden boundary for Zone 2 training: In recent years, “polarized training” has emphasized large volumes of Zone 2 (below LT1). Knowing the power at LT1 precisely ensures that your LSD sessions don’t inadvertently drift into Zone 3 (steady lactate metabolism zone, which offers less training benefit than pure aerobic Zone 2).
2. LT2 ≈ FTP, but not exactly equal: Individual differences exist; some athletes have an FTP corresponding to 3.5 mmol/L of lactate, while others sit at 5.0 mmol/L. This is a normal range of metabolic individual variation.
3. Be mindful of heat accumulation when testing in Taiwan’s summer: In high-temperature environments, elevated heart rate shifts the power–lactate curve to the left. Testing in the early morning or in an air-conditioned indoor environment is recommended.
4. LT2 power will rise after training improvements: After effective training, the power corresponding to the same lactate concentration (e.g., 4 mmol/L) increases. This is the core meaning of “tracking progress through lactate testing.”
5. Avoid fatigue before testing: Lactate testing must be performed in a well-rested state. Avoid high-intensity training for two days prior; otherwise, the lactate curve will shift left, underestimating your true LT1/LT2 power.

Conclusion

Although blood lactate testing is more complex and expensive than FTP testing, it provides the most direct and most individualized basis for setting training zones. For amateur cyclists, undergoing one lactate test per year, combined with regular FTP monitoring, constitutes the most complete training science tracking protocol. By understanding the lactate curve, you will be able to control training intensity with greater precision—ensuring Zone 2 truly falls within the aerobic metabolism range, threshold training lands precisely near LT2, and every watt of training delivers maximum benefit.

Related Reading

• Lactate Threshold Training: How to Find Your Critical Cycling Pace
• Lactate Threshold Testing Methods: Accuracy Comparison Between Laboratory and Field Tests
• Portable Lactate Analyzers: Practical Operation and Training Applications for Running Lactate Threshold Testing
• Ventilatory Threshold and Lactate Threshold: Similar but Not Identical Physiological Boundaries