Why is Your FTP not improving?

You've been consistent. You're hitting your intervals. Your TSS is high, but your FTP hasn't moved in six months — maybe longer. Every eight weeks you run another ramp test, and the number sits there unchanged or even trending downwards.

If you're wondering "why is my FTP not improving despite structured training", the answer almost certainly isn't that you need to work harder. It's that you're training without knowing what's actually limiting you. FTP might show you that you've plateaued, but it tells you nothing about why. And until you know why, you're guessing.

The Standard Advice Is Wrong

The go-to responses when FTP plateaus usually sound something like this: add more threshold work, boost your CTL, do more Zone 2. Sometimes it's the opposite — "you're overreaching, back off and let adaptation catch up."

All of this is plausible. None of it is specific to you.

FTP is an output. It's the downstream result of a complex interaction between your aerobic capacity (VO2max), your glycolytic system (VLaMax), and the efficiency with which your body manages lactate at sub-maximal intensities. Chasing FTP directly — by doing more FTP work — is like treating a symptom without diagnosing the disease. In some cases it helps. In many cases, especially for cyclists who've been training consistently for years, it makes the problem worse.

What's Actually Happening Physiologically

Your functional threshold (LT2) is the highest intensity at which your body can sustain a steady-state lactate clearance. Above it, lactate accumulates. Below it, your aerobic system keeps pace. That balance point is what your FTP is approximately measuring.

Here's the part most training plans ignore: LT2 isn't just a function of how fit your aerobic system is. It's also determined by how aggressively your glycolytic system produces lactate in the first place.

That production rate is called VLaMax — maximal lactate production rate, measured in mmol/L/s. A high VLaMax means your muscles generate lactate rapidly under glycolytic stress. A lower VLaMax means that production rate is blunted, and your aerobic system has less lactate to contend with at any given intensity.

Two athletes. Identical VO2max. Identical training history. One has a VLaMax of 0.65, the other 0.32. At 250 watts, the high-VLaMax athlete is producing enough lactate to push themselves toward — or past — their threshold. The low-VLaMax athlete is comfortably aerobic. Same power. Completely different physiological state.

If you have a high VLaMax, your LT2 is functionally capped. Your threshold is being suppressed not because your aerobic system is weak, but because your glycolytic system is generating too much lactate for your aerobic system to clear at threshold pace. No amount of threshold intervals will fix this — they'll just keep VLaMax elevated, or push it higher.

There's a second consequence that compounds the problem: FatMax suppression. High VLaMax doesn't just cap threshold. It also shifts your fuel utilization toward carbohydrates at intensities where you should be burning primarily fat. Your fat oxidation rate — FatMax — drops. You're burning glycogen on three-hour rides that should be aerobic base work. You're not recovering between sessions. You're also not building the fat-burning engine that underpins endurance capacity.

This is why your FTP hasn't moved. You're not undertrained. You're metabolically skewed, and no ramp test will show you that.

What This Means for Your Training

Once you understand the mechanism, the training prescription changes significantly.

If a high VLaMax is suppressing your threshold, the fix is not more threshold work. The fix is a training block specifically designed to reduce VLaMax — which means sustained, genuinely low-intensity aerobic work done at or below LT1.

The problem: most cyclists' "Zone 2" is too hard. Zone 2 defined as 55-75% of FTP is a percentage of an output number that already has VLaMax baked into it. For a cyclist with a high VLaMax, that Zone 2 range often sits above LT1 — meaning they're generating lactate on every "easy" ride, stimulating the glycolytic system, and never giving VLaMax a reason to adapt downward.

Real LT1 is a physiological marker. It's the intensity below which lactate flux is genuinely stable and fatty acid oxidation is dominant. It's not a fixed percentage of FTP. It varies by individual, by fitness phase, and — critically — by VLaMax. For a high-VLaMax athlete, LT1 might be at 180 watts. For a low-VLaMax athlete with the same FTP, it might be at 230 watts.

Training below true LT1 over an extended block — six to twelve weeks — drives measurable VLaMax reduction. Lactate production at sub-maximal intensities decreases. The aerobic system gains ground. LT2 rises. FTP follows.

The other intervention is targeted glycolytic suppression: specifically avoiding high-intensity glycolytic work during a VLaMax reduction block. Short punchy efforts, standing starts, and unstructured group ride surges all stimulate VLaMax. If the goal is to bring it down, those need to come out of the training mix temporarily.

For the athlete who's been training hard for years without seeing FTP gains, this is almost always the missing piece. Not more volume. Not harder intervals. A strategic metabolic reset targeting the specific mechanism that's keeping threshold suppressed.

This Is Why INSCYD Exists

Everything above is actionable in principle. In practice, it's nearly impossible to execute without knowing your actual numbers.

What is your VLaMax? Is it 0.4 or 0.7? Where exactly is your LT1 in watts — not as a percentage of FTP, but as a lactate-validated power output? What's your FatMax? How much fat are you actually oxidizing at 200 watts versus 240 watts?

These questions don't have guessable answers. They have measured ones.

An INSCYD metabolic test gives you VLaMax, VO2max, LT1, LT2, FatMax, and CarbMax from a structured field or lab protocol. With those values, the training prescription isn't generic — it's built around your actual physiology. Your LT1 in watts. Your VLaMax reduction target. Your specific Zone 2 power range, not a percentage estimate.

This is what WorldTour teams have used for over two decades. The reason your FTP hasn't improved isn't that the science doesn't exist. It's that most coaching approaches don't have access to the data needed to apply it.

Stop Guessing at the Problem

If your FTP hasn't moved, you're not stuck. You're training without enough information.

The plateau isn't a ceiling. It's a diagnostic gap. And the data to close that gap is available — it just requires actually measuring what's happening in your metabolism, not inferring it from a 20-minute test.

Ready to find out what's actually limiting your threshold? An INSCYD metabolic test gives you the full picture in under an hour. Book your test →

Or start with the physiology: What Is VLaMax and Why Does It Matter? →