Here's something that catches a lot of self-coached cyclists off guard. The number you've spent the last three years chasing — your FTP — is one of two thresholds that matter for how you should be training, and it's not even the more important one. The one most riders have never heard of, never tested, and never set their easy days against, is doing more to wreck their progress than any other invisible variable.
That number is LT1 — the aerobic threshold. It's the line between truly easy riding and the grey zone. Get it wrong by 15 watts and your zone 2 isn't zone 2 anymore. Multiply that across every easy ride for a year and you've quietly converted hundreds of hours of intended base work into low-grade tempo. The body never gets the easy adaptation. The hard sessions never have the legs to deliver. Same training plan on paper, completely different physiological outcome.
Until recently the only way to find LT1 with any precision was a lab test. Now a finger-stick meter, a smart trainer, and an honest hour gives you most of what the lab would tell you. This is one of the useful tools that's filtered down from the World Tour to the serious amateur in the last few years. If you take training seriously and you're still working from FTP percentages alone, this is the upgrade.
Why FTP Isn't Enough
FTP is a useful number. It's not a wrong number. It's a single capacity ceiling — your roughly sustainable hour power. Most online plans translate it into seven training zones using fixed percentages (zone 2 is 56–75% of FTP, zone 4 is 95–105%, and so on). That's clean, easy to teach, and it works well enough for many cyclists most of the time.
The problem is that the relationship between FTP and your actual physiological thresholds isn't fixed. Two riders with identical FTPs can have wildly different LT1s. One has a deep aerobic base — LT1 might sit at 70% of FTP. The other has built FTP through endless threshold work — LT1 might sit at 55% of FTP. The standard zone 2 prescription of 56–75% works for the first rider and ruins the second.
When I had Professor Seiler on the podcast, he was deliberate about this distinction. The polarised training model isn't built on FTP percentages. It's built on the two thresholds — easy work below LT1, hard work above LT2, and almost nothing in between. Without measuring those two points, you're approximating, and the approximation gets worse the longer you've been training.
What LT1 and LT2 Actually Are
The simple version. Lactate is a normal byproduct of energy metabolism. At rest, blood lactate sits around 1 mmol/L. As exercise intensity rises, lactate production rises with it. So does lactate clearance — your body is shuttling lactate around and using it as fuel.
For most of a typical ride, production and clearance balance. Lactate stays roughly stable. At a certain intensity, production starts to outpace baseline clearance. That's LT1 — the first lactate inflection point, around 2 mmol/L. You can still hold this intensity for a long time, but you've left the deep aerobic zone behind. Your body is using more carbohydrate, less fat. The adaptation profile shifts.
Push harder still and at some point lactate production accelerates beyond what clearance can handle even at increased intensity. Lactate starts climbing rapidly. That's LT2 — the second inflection point, around 4 mmol/L. This is roughly where your maximal lactate steady state sits. It's similar to FTP but tied to a physiological event rather than a time-trial result.
Between LT1 and LT2 sits the grey zone. Most amateur cyclists live here far too much. Too hard to be truly easy, not hard enough to drive the high-intensity adaptations. Easy rides drift up. Hard sessions drift down. Everything ends up in the middle. The pros do the opposite — they live below LT1 most of the time and above LT2 the rest, with very little in the grey zone.
This is the gap a lactate test closes. It tells you exactly where your two lines are.
What a Home Test Actually Costs
The kit list, with rough USD pricing as of 2026:
- Lactate meter. The Lactate Plus is the most popular masters cyclist option at around $250. The Edge or Scout meters are priced similarly. There's no real way around this cost — it's the central piece of equipment.
- Test strips. Around $80–120 for a box of 25. You'll burn through 6–8 in a single test. Three or four tests a year and a box lasts most of the season.
- Lancets and alcohol wipes. Around $15–20 for plenty of both.
- Plaster pack. Self-explanatory. Cheap.
So roughly $250 for the meter, then $20–30 per test in consumables. For a self-coached cyclist who might otherwise pay $150–250 for a single lab test, the kit pays for itself inside a season.
A few things to know before you buy. Calibration strips are required when you start a new box of test strips — most boxes include them. Different meters use different strip ranges; pick one and stick with it for repeatability. The Lactate Plus is the one most cycling coaches reference but the others work fine if you're consistent.
The Step Test Protocol
There are several test formats. The cleanest and most repeatable for a self-coached cyclist is a 5-minute step test, run on a smart trainer or a flat road where you can hold steady power.
Warm up. 15–20 minutes easy. Two or three short pickups at the end to wake the legs up. Have your lancets, strips, alcohol wipes, and meter laid out before you start.
The step. Start at a power well below your suspected LT1 — for most masters cyclists that's around 50% of FTP. Hold that power for 5 minutes. In the last 30 seconds, draw a small drop of blood from a fingertip (the side of the fingertip is less painful than the pad), test it on the meter, and record the value alongside the average power and average heart rate of the step.
Step up. Increase power by 20–25 watts. Hold the new power for 5 minutes. Test again at the end. Repeat.
End the test. Stop when lactate is clearly above 4 mmol/L and rising fast — usually 5–6 mmol/L is plenty. You don't need to grind to the top. The point is to find the inflection points, not max yourself out.
Plot it. On the y-axis, lactate. On the x-axis, power. The curve will start almost flat, then bend upward — that's LT1. It'll bend again more steeply — that's LT2. You can do this on graph paper or in a spreadsheet. TrainingPeaks lets you log the values directly against the workout, which makes it easy to compare tests over time.
A few practical notes. Use the second drop of blood, not the first — the first contains tissue fluid that contaminates the reading. Wipe the finger with the alcohol wipe and let it dry before lancing. Keep a notebook by the trainer. The whole test takes 45–60 minutes including warm-up.
Reading Your Results
Plot the curve. Most masters cyclists end up with something like:
- LT1 around 60–75% of FTP, depending on aerobic depth.
- LT2 around 90–100% of FTP, depending on how the FTP was estimated.
- A clear "knee" in the curve at each threshold, even if it's not perfectly sharp.
Now you have working numbers. Easy rides — below LT1. Threshold work — at LT2. VO2max work — above LT2. Sprint work — well above. The standard percentage-based zones should agree with these numbers; if they don't, trust the lactate test, not the percentages.
The number that catches most masters cyclists by surprise is LT1. Plenty of riders find it sits 10–20 watts lower than the top of their "zone 2" as defined by FTP percentages. Which means every "easy" ride for the last six months has been quietly drifting into early tempo. That's the silent leak the test exposes.
How the Pros Use This
When I had John Wakefield on the podcast about how Bora-Hansgrohe build their athletes, he was explicit. The first thing a pro does at the start of every block is establish where the thresholds are. Not estimate. Not assume the previous block's numbers carry. Actually measure.
The reason is that LT1 in particular moves seasonally. After a long base block, it rises. After heat training, it can shift. After illness, it drops. Training off out-of-date numbers is one of the most common quiet causes of underperformance among self-coached athletes. The pros refuse to do it. They test, set zones, train against the current numbers, retest, repeat.
You don't need to test as often as a pro. You're not racing every weekend. But the principle is the same — work from current numbers, not last year's numbers.
Why This Matters Most for Polarised Training
If you're following a polarised plan — which most serious masters cyclists eventually end up on — knowing LT1 is non-negotiable. The whole model rests on the discipline of staying below it on easy days. Without that line measured, "easy" becomes a feel that drifts upward over time.
The grey zone problem is the most common training error in masters cycling. It looks like dedication. It feels like training hard. It produces less than half the result of properly polarised work. The lactate test is the single cleanest way to see whether you're actually doing what you think you're doing.
This is also why home lactate testing pairs so well with aerobic decoupling testing. Lactate tells you where your zones are. Decoupling tells you whether your aerobic base actually supports the duration you're asking it to. Run both, three or four times a year, and you have a far more honest picture of your fitness than any FTP test or Strava heatmap will give you.
When Not to Bother
Lactate testing isn't for everyone. If you're new to structured training, start with FTP-based zones, get consistent at training, build a base, and stop worrying about marginal-gain tools you don't yet need. Most cyclists training fewer than 6 hours a week will get more from disciplined zone 2 work and a sensible plan than from a fancy test.
The rider who benefits from this is the masters cyclist who's been training seriously for two or more years, has a clear understanding of polarised training, has hit a plateau or wants to optimise the next block, and is willing to actually act on the numbers — meaning if the test reveals their LT1 is 15 watts below where they thought, they're prepared to ride 15 watts easier on every easy ride for three months.
If you're not going to act on the data, don't run the test.
How to Use the Numbers Day to Day
Once you have your LT1 and LT2, the practical translation is simple:
- Easy rides. Power below LT1. Heart rate generally below the heart rate you saw at LT1 in the test. Conversation pace.
- Threshold work. Intervals at or just below LT2. Most riders prescribe these as 2 × 20-minute or 3 × 12-minute blocks.
- Sweet spot. Between LT1 and LT2 — useful in moderation, dangerous if it becomes the default for everything.
- VO2max. 105–115% of LT2 power. Three- to five-minute intervals, 4–6 reps, full recovery.
If you're following a TrainingPeaks plan or building one yourself, plug the new zones into the platform and let the workouts auto-target the right numbers.
How This Connects to the Plateau Conversation
A lot of cyclists arrive at lactate testing because they're stuck. FTP isn't moving. The training they've been doing for months hasn't translated. The number they're getting from the test usually tells them the same story — their LT1 is well below where they assumed it was. The "easy" rides have been too hard. The hard sessions haven't had the legs to deliver because the system has been chronically under-recovered.
That's a fixable problem. Drop easy ride power to genuine LT1 for six to eight weeks. Hold the volume. Hit the hard sessions properly. Retest. The numbers move.
If you've stalled and you're not sure why, the Plateau Diagnostic walks through the four most common limiters and points you at the right next step. It takes four minutes and it's free.
A Realistic Plan for Bringing This Into Your Year
Most masters cyclists who use lactate testing well do something like this:
- Start of base season (October–November). Test once. Set zones. Train below LT1 most of the time, with one or two structured sessions a week.
- End of base block (January). Retest. Confirm LT1 has moved up and the curve is shifting right. If LT1 hasn't moved, look at sleep, fuelling, bloods, and stress before changing the training.
- Mid-build (March–April). One more test. Confirm LT2 is rising before the key event. Adjust threshold-session targets to match.
- Race season. No more testing. Trust the work.
That's three tests in a year. About 20 strips. A few hours of total time on the trainer. For the masters cyclist taking training seriously, it's the cheapest, most useful diagnostic kit you'll buy.
For more on what these numbers actually look like in practice, the zone 2 training complete guide goes deeper on what to do once you have your LT1, and the polarised training guide shows how to build the week around the two thresholds. If you've been running purely off FTP percentages and you're starting to feel the gap, this is the upgrade.
The riders who use this well don't treat it as a status symbol. They treat it as data. Test, train, retest, train. The numbers move. The legs follow.