Lactate Threshold vs FTP: A Thorough Scientific Clarification

In the world of cycling training, “lactate threshold” and “FTP (Functional Threshold Power)” are the two concepts most frequently used interchangeably and misunderstood. Some riders think they are the same thing; others know they differ but cannot clearly explain how. This article thoroughly clarifies these two concepts from a sports physiology perspective.

What Is Lactate?

First, let’s clear up a long-standing myth: lactate is not “waste,” nor is it the culprit behind muscle soreness.

Lactate (Lactic Acid, more precisely lactate salt) is a metabolic byproduct of cells during high-intensity exercise, but it is also an important fuel source—it can be used directly by other muscle fibers, the heart, and the liver.

The “burning sensation” in muscles mainly comes from hydrogen ions (H⁺) produced during exercise, which alter the pH balance of the muscle environment. Lactate is actually a “byproduct buffer” in this process.

The Scientific Definition of Lactate Threshold

LT1 (First Lactate Threshold)

• Definition: The power output at which blood lactate concentration begins to rise steadily, typically corresponding to approximately 2 mmol/L of blood lactate
• Significance: Below LT1 intensity, lactate production and clearance are in balance, allowing exercise to continue indefinitely
• Corresponding training zone: Zone 1-2 (easy aerobic)

LT2 (Second Lactate Threshold)

• Definition: The “inflection point” where blood lactate concentration rises rapidly, typically corresponding to 4 mmol/L of blood lactate (but with high individual variability)
• Significance: Above LT2 intensity, lactate accumulates quickly, and the energy system shifts toward anaerobic metabolism
• Corresponding training zone: Zone 4 (threshold training)

The Definition of FTP (Functional Threshold Power)

FTP was proposed by Hunter Allen and Dr. Andrew Coggan in the 2000s, defined as:

“The highest average power a rider can sustain for 60 minutes under optimal conditions.”

Practical FTP Testing Methods

Standard 20-Minute Test Protocol

1. Warm up thoroughly (15-20 minutes, including several 30-second sprints)
2. Ride an all-out 20-minute time trial
3. 20-minute average power × 0.95 = FTP estimate

The 0.95 multiplier is used because maximal 20-minute power is typically about 5% higher than 60-minute power.

Ramp Test

Increase power by 20W every minute until exhaustion:

• FTP ≈ Power of the last completed minute × 0.75
• Advantages: Short duration (about 25 minutes), less mental stress

The Relationship Between FTP and LT2

FTP and LT2 are highly correlated, but not identical:

Research shows that FTP is typically 3-8% lower than the power corresponding to LT2, because most people cannot sustain true LT2 power for 60 minutes.

Why Does This Distinction Matter?

Precision of Training Intensity

If you use FTP as the basis for training intensity, you need to know:

• Sweet Spot (approximately 88-93% FTP) is close to but slightly below LT2
• Threshold training (95-105% FTP) is approximately equivalent to intensity near LT2
• VO2max training (106-120% FTP) is clearly above LT2

Goals of Threshold Training

Methods to raise the threshold (LT2):

1. Sweet Spot training: Long durations (20-60 minutes) riding at 88-93% FTP
2. Threshold intervals: 3-5 minutes × multiple sets, at 100-105% FTP intensity
3. Transitional long rides: 2-4 hours of easy Zone 2 riding to enhance fat oxidation capacity

How to Use These Metrics to Improve Performance?

Establishing Your Personal Baseline

1. Perform an FTP test to establish your training baseline
2. If possible, undergo lactate testing to understand the precise positions of LT1 and LT2
3. Retest regularly (every 6-8 weeks) to track progress

Training Distribution Recommendations

According to research on “polarized training” (Stephen Seiler et al.):

• 80% of training time: below LT1 (Zone 1-2)
• 20% of training time: above LT2 (Zone 4-5)
• Minimize time spent in the “moderate-intensity gray zone” (Zone 3, between LT1 and LT2)

Conclusion

Lactate threshold and FTP are two keys to understanding cycling training. FTP provides a practical metric that is easy to test and track; understanding the lactate threshold helps you know why certain training intensities work and others do not. By combining the two, you can design a truly scientific training plan.

Related Reading

• The Physiological Mechanisms of Functional Threshold Power (FTP): A Detailed Analysis of the Lactate Balance Point
• Lactate Threshold Training: How to Find Your Critical Cycling Pace
• Cycling Lactate Threshold Training: Designing Sweet Spot 88–93% FTP Intervals
• Ventilatory Threshold and Lactate Threshold: Similar but Distinct Physiological Boundaries