Why lactate threshold matters more than VO2max for endurance performance
Introduction
In the world of endurance cycling, two physiological metrics dominate the conversation: VO2max and lactate threshold. While VO2max—your maximum oxygen uptake capacity—often gets the spotlight as the ultimate measure of aerobic fitness, it's actually your lactate threshold that serves as the single best predictor of endurance performance. Understanding the distinction between these two metrics, and more importantly, how to train your lactate threshold, can transform your racing and training strategy.
Think of VO2max as the size of your engine—it sets your physiological ceiling. But lactate threshold determines what percentage of that engine you can actually use for sustained efforts. A rider with a moderate VO2max but a high lactate threshold will consistently outperform someone with a superior VO2max but a lower threshold. This article explores the science behind lactate threshold, why it matters, and how to train it effectively.
What Is Lactate Threshold?
Lactate threshold (LT) refers to the exercise intensity at which lactate—a byproduct of anaerobic metabolism—begins to accumulate in the bloodstream faster than it can be cleared. Despite common misconceptions, lactate itself isn't the "bad guy" causing muscle fatigue. Rather, it's a valuable fuel source that your body can use when metabolized properly.
At low to moderate intensities, your body produces lactate continuously, but it's efficiently cleared and recycled by the liver, heart, and working muscles. However, as intensity increases, lactate production eventually exceeds clearance capacity, leading to accumulation. This point—where the lactate curve steepens—marks your lactate threshold.
In practical terms for cyclists, lactate threshold corresponds closely to what's commonly called functional threshold power (FTP)—the highest average power you can sustain for approximately one hour. It's also related to the concept of , the highest intensity at which lactate production and clearance remain in equilibrium.
Lactate Threshold vs. Anaerobic Threshold: Clarifying the Terminology
The terms "lactate threshold" and "anaerobic threshold" are often used interchangeably, but they represent slightly different concepts. The anaerobic threshold theoretically marks the point where anaerobic metabolism becomes the dominant energy system. However, this is somewhat misleading—anaerobic and aerobic metabolism don't operate as distinct on-off switches but rather exist on a continuum.
Lactate threshold is the more precise and measurable term, referring specifically to the point of lactate accumulation. In practice, both terms describe the same general intensity range where sustainable power begins to decline rapidly. For cyclists, focusing on threshold power—measurable via power meters—provides the most practical framework for training.
Why Lactate Threshold Matters More Than VO2max
While VO2max represents your absolute physiological ceiling, it's a relatively fixed trait in trained athletes. Elite cyclists might have VO2max values ranging from 70-85 ml/kg/min, but the winner of a race isn't necessarily the rider with the highest number. Instead, it's the rider who can sustain the highest percentage of their VO2max for the duration of the event.
This is where lactate threshold becomes critical. Your threshold intensity is typically expressed as a percentage of VO2max. An untrained individual might only sustain 50-60% of VO2max at threshold, while an elite endurance athlete can sustain 85-90% or higher. This difference in sustainable power explains why professional cyclists can maintain such high speeds for hours on end.
Consider two hypothetical riders:
Rider A: VO2max of 75 ml/kg/min, lactate threshold at 65% of VO2max
Rider B: VO2max of 65 ml/kg/min, lactate threshold at 85% of VO2max
Despite Rider A's higher absolute ceiling, Rider B can sustain a higher absolute workload at threshold (65 × 0.85 = 55.25 vs. 75 × 0.65 = 48.75). Over the course of a long race, Rider B will outperform Rider A, assuming similar efficiency and tactics.
The Physiology Behind Lactate Metabolism
To understand how to improve lactate threshold, we need to understand what's happening at the cellular level. Lactate production occurs primarily in fast-twitch muscle fibers during glycolysis—the breakdown of glucose for energy. When the demand for ATP (cellular energy) exceeds what can be supplied through aerobic metabolism alone, pyruvate is converted to lactate.
Here's the key insight: lactate isn't a waste product. It's actively transported to slow-twitch muscle fibers, the heart, and the liver, where it's converted back to pyruvate and used as fuel. This process is called the lactate shuttle. Your body's ability to clear and recycle lactate is trainable—and this is precisely what threshold training improves.
Training at and around threshold intensity enhances several physiological adaptations:
Increased mitochondrial density: More mitochondria mean greater capacity for aerobic metabolism, reducing reliance on anaerobic pathways
Improved lactate clearance: Better lactate transporter expression and enzyme activity enhance your ability to shuttle and metabolize lactate
Enhanced capillary density: More blood vessels in working muscles improve oxygen delivery and waste removal
Greater metabolic flexibility: Improved ability to switch between fat and carbohydrate metabolism, preserving glycogen stores
Training Zones and Lactate Threshold
Threshold training doesn't mean riding at exactly your FTP every session. In fact, the most effective approach involves training in a range around threshold, commonly divided into these zones:
Tempo (Zone 3): 76-90% of FTP—builds aerobic base and improves fat oxidation
Sweet Spot (Upper Zone 3/Lower Zone 4): 88-93% of FTP—maximizes training stimulus while remaining sustainable
Threshold (Zone 4): 91-105% of FTP—directly targets lactate clearance and threshold power
VO2max (Zone 5): 106-120% of FTP—improves oxygen uptake and pushes your physiological ceiling
Sweet spot training has become particularly popular because it provides roughly 90% of the training benefit of threshold work with significantly less fatigue and faster recovery. This allows for higher training volume and frequency, which can lead to greater cumulative adaptations.
How to Identify Your Lactate Threshold
There are several methods to determine your lactate threshold, ranging from laboratory testing to field-based estimates:
Laboratory Testing
The gold standard involves an incremental exercise test with blood lactate sampling. You'll ride at progressively higher intensities while technicians draw small blood samples to plot your lactate curve. The point where lactate begins to accumulate (typically around 4 mmol/L, though individual variation exists) marks your threshold. This method provides the most accurate data but requires specialized equipment and expertise.
Field Testing: FTP Tests
For practical purposes, most cyclists use FTP as a proxy for lactate threshold. Common FTP test protocols include:
20-minute test: After a proper warm-up, ride as hard as you can sustain for 20 minutes. Your average power multiplied by 0.95 estimates your FTP
2×8-minute test: Perform two 8-minute all-out efforts with 10 minutes recovery between. Average the two efforts for your FTP estimate
Ramp test: Increase power by 20-30 watts every minute until failure. FTP is estimated at approximately 75% of your peak 1-minute power
While not as precise as lab testing, these field tests are highly repeatable and provide actionable training zones.
Monitoring During Training
Modern power meters and heart rate monitors allow you to track threshold performance over time. Pay attention to your power at a given heart rate or perceived exertion—if you're sustaining higher power at the same heart rate, your threshold is improving.
Effective Threshold Training Protocols
Building threshold power requires consistent, focused training. Here are proven workout structures:
Classic Threshold Intervals
2×20 minutes at 95-100% FTP with 10 minutes recovery remains a staple threshold workout. It provides sufficient stimulus to drive adaptation while remaining achievable for most trained cyclists.
Sweet Spot Intervals
3×15 minutes at 88-92% FTP with 5 minutes recovery offers high training stress with moderate fatigue, making it suitable for frequent execution during base-building phases.
Over-Under Intervals
Alternate between 2 minutes slightly below threshold (95% FTP) and 1 minute slightly above (105% FTP) for 4-6 repetitions. This workout specifically trains lactate clearance by forcing your body to process accumulating lactate during the "over" portions.
Tempo Rides
Long steady efforts at 75-85% FTP (60-90 minutes) build aerobic endurance and improve fat oxidation, creating a stronger foundation for threshold work.
Periodization and Progression
Threshold training should be periodized throughout your season. During base phases, focus on tempo and sweet spot work to build aerobic capacity with manageable fatigue. As you approach racing season, incorporate more specific threshold and over-under intervals. Include VO2max work to push your ceiling higher, which in turn allows your threshold to rise.
Progression should be gradual. Increase either volume (total time at intensity) or intensity (percentage of FTP), but not both simultaneously. A common approach is to add 5-10 minutes of total interval time per week until reaching your target volume, then maintain that volume while periodically testing and adjusting zones.
The Role of Recovery and Nutrition
Threshold adaptations occur during recovery, not during the workout itself. Adequate rest, sleep, and nutrition are essential for improving lactate clearance and mitochondrial function. Carbohydrate availability is particularly important—training with low glycogen stores ("train low") can enhance metabolic adaptations, but should be used strategically, as it can compromise workout quality.
Post-workout nutrition should prioritize carbohydrate replenishment and protein for muscle repair. Consuming 1.0-1.2 g/kg of carbohydrates within 30-60 minutes after threshold sessions helps restore glycogen and prepare for subsequent training.
Common Mistakes in Threshold Training
Training too hard, too often: Every ride shouldn't be a threshold session. Follow the 80/20 rule—80% of training at low intensity, 20% at high intensity
Neglecting easy days: Recovery rides at very low intensity (under 60% FTP) facilitate adaptation and prevent overtraining
Ignoring FTP changes: Retest every 6-8 weeks and adjust training zones accordingly
Poor pacing in intervals: Starting too hard leads to premature fatigue and incomplete intervals. Negative splitting (finishing stronger) indicates better pacing
Conclusion: Threshold as the Foundation of Endurance Performance
While VO2max sets your physiological potential, lactate threshold determines how much of that potential you can actually deploy in competition. By understanding the mechanisms behind lactate metabolism and implementing strategic threshold training, you can systematically improve your sustainable power and race performance.
The key is consistency and proper periodization. Focus on sweet spot and tempo work during base phases, incorporate specific threshold intervals as competition approaches, and maintain balance with adequate recovery. Monitor your progress through regular testing and adjust your zones as your fitness improves.
Remember: the goal isn't to ride at threshold all the time, but to progressively raise the intensity at which your body can maintain metabolic equilibrium. With patient, intelligent training, you can shift your lactate curve to the right—sustaining higher power outputs for longer durations, and ultimately, achieving better results on race day.
