← Back to blog
Training Science March 28, 2026 5 min read

What is VLaMax and Why Your FTP Zones Are Wrong

If you train with power, you probably know your FTP. You might even test it regularly. But here’s the uncomfortable truth: FTP-only power zones are a rough approximation at best, and misleading at worst.

The problem isn’t FTP itself. It’s that FTP tells you one thing — your threshold — and tries to derive everything else from percentages of that single number. Your Zone 2 is not “55-75% of FTP” for everyone. It depends on your metabolism.

Enter VLaMax.

What is VLaMax?

VLaMax (maximum rate of lactate production) measures how fast your body produces lactate during high-intensity efforts. It’s the glycolytic counterpart to VO2max.

  • VO2max tells you how big your aerobic engine is — how much oxygen your body can use.
  • VLaMax tells you how powerful your anaerobic engine is — how fast you burn carbohydrates and produce lactate.

Together, they define your metabolic profile. And that profile determines where your zones actually fall.

Why it matters for training

A cyclist with a high VLaMax (say, 0.6 mmol/L/s) produces lactate quickly. Their body burns through glycogen fast, hits threshold earlier, and struggles on long efforts. They might have a decent FTP but fade badly after hour 2.

A cyclist with a low VLaMax (say, 0.3 mmol/L/s) produces lactate slowly. They’re efficient, can ride at higher percentages of FTP for longer, and burn more fat at moderate intensities. They’re built for endurance.

Same FTP. Completely different athletes. Completely different zone prescriptions.

The problem with 5-zone FTP models

Traditional 5-zone models (like Coggan’s) derive everything from FTP:

  • Zone 1: <55% FTP
  • Zone 2: 56-75% FTP
  • Zone 3: 76-90% FTP
  • Zone 4: 91-105% FTP
  • Zone 5: >106% FTP

These percentages are averages across a population. They work okay for the “average” athlete. But you’re not average — nobody is.

The real-world problems:

  • Your “Zone 2” might actually be Zone 3 intensity for your metabolism, meaning your easy rides aren’t easy enough
  • Your “threshold” zone might be too narrow or too wide depending on your VLaMax
  • You might be doing “sweet spot” training at an intensity that’s actually hammering your glycolytic system instead of building aerobic capacity

This is why some athletes train for years and plateau. They’re training in the wrong zones for their metabolism.

7-zone metabolic model

When you know both VO2max and VLaMax, you can calculate actual metabolic transitions — not arbitrary FTP percentages. The Mader bioenergetic model does exactly this.

The result is a 7-zone model based on real metabolic thresholds:

  1. Recovery — below fat oxidation peak
  2. Endurance — fat max to aerobic threshold
  3. Tempo — aerobic threshold to below FTP
  4. Threshold — around FTP / MLSS
  5. VO2max — above threshold to VO2max power
  6. Anaerobic — above VO2max, high glycolytic demand
  7. Neuromuscular — max power, short duration

The boundaries between these zones are calculated from your actual VO2max and VLaMax values, not from FTP percentages. Two athletes with the same FTP will have different zone boundaries if they have different VLaMax values.

How to estimate VLaMax without a lab

Lab testing is the gold standard — a step test with blood lactate samples at each stage. But it costs $200-400, requires a sports lab, and gives you a single snapshot.

The Mader model can estimate VLaMax from regular ride data by analyzing the relationship between power output and heart rate at submaximal intensities. It’s not as precise as a blood test, but:

  • It’s accurate within ~10% of lab values
  • It updates with every ride, getting more accurate over time
  • It costs nothing beyond riding your bike with a power meter

The key insight: your heart rate response at different power outputs reveals your metabolic efficiency. A higher heart rate at the same power suggests more anaerobic contribution (higher VLaMax). A lower heart rate suggests better aerobic efficiency (lower VLaMax).

What to do with this information

If your VLaMax is high (>0.5 mmol/L/s):

  • You’re burning carbs fast and producing lactate quickly
  • Prioritize long Zone 2 rides to build aerobic base and lower VLaMax
  • Reduce high-intensity interval volume — you’re already glycolytically strong
  • Focus on fat oxidation and metabolic efficiency
  • Your real Zone 2 is probably lower than what FTP-based models tell you

If your VLaMax is low (<0.35 mmol/L/s):

  • You’re aerobically efficient but may lack top-end power
  • Add more high-intensity intervals (VO2max, anaerobic work)
  • Your aerobic base is strong — now build the engine on top
  • Your real Zone 2 ceiling is probably higher than FTP models suggest

If your VLaMax is moderate (0.35-0.5 mmol/L/s):

  • You’re balanced — training focus depends on your goals
  • Gran fondo? Lower VLaMax further for durability
  • Criterium? Push VLaMax higher for repeated surges
  • Time trial? Optimize the balance for sustained power

The bottom line

FTP is a useful number. But it’s one number. Training with 5 zones derived from a single threshold measurement is like navigating with only a compass — you know the general direction, but you’ll miss the turns.

VLaMax gives you the second coordinate. With both VO2max and VLaMax, you get a metabolic map that tells you exactly what your body does at every intensity. Your zones become personalized prescriptions, not population averages.

The athletes who break through plateaus are the ones who stop training by the numbers and start training by their metabolism.

Watts estimates your VO2max and VLaMax from regular training data using the Mader model — no lab required. Your 7-zone prescription updates with every ride.