What Exactly Is the Lactate Threshold? A Complete Clarification from Lactate's Redemption to LT1, LT2, and FTP

In Taiwan’s cycling community, “threshold” is probably the term most often on people’s lips, yet also most often misunderstood. Some treat it as a fixed power number to chase all year round; others equate it with lactate, thinking “lactate accumulation” means sore legs or hitting the wall; and some have heard the long string of abbreviations—LT1, LT2, MLSS, CP, OBLA—but no one has ever properly explained whether they all refer to the same thing.

This article has a simple mission: to clarify the story of lactate, a molecule that has been wrongfully blamed for decades; to explain the difference between LT1 and LT2; to organize the relationships among all those terms into a reference table; and then to tell you—a Taiwanese cyclist with a power meter or heart rate strap—how to estimate your two thresholds in a relatively safe, relatively repeatable way on Wuling, Fengguizui, Beiyi, or the riverside bike paths, and actually put them to use in your training.

---

1. What Lactate Was Wrongfully Accused Of

1.1 “Lactate Is Waste”—Wrong

For a long time, the textbook story went like this: at high exercise intensity, oxygen is insufficient, so the body resorts to the “anaerobic” pathway, producing lactate as a metabolic waste product. Lactate accumulation makes muscles acidic, painful, and unable to contract, so you slow down.

This story sounds coherent, but nearly every sentence needs correction.

Let’s start with the most basic point: lactate is not produced only under oxygen deprivation. Glycolysis—the process of breaking down glucose or glycogen into pyruvate—is happening right now as you read this article, just at a very low rate. Once pyruvate is produced, it has two paths: one is to enter the mitochondria and be oxidized for energy; the other is to be converted into lactate by lactate dehydrogenase in the cytoplasm. Both paths are always active, and their proportions shift with intensity. In other words, even at rest with fully adequate oxygen supply, lactate is always present in the blood, just at a low concentration.

So “lactate present equals oxygen deprivation” is a false inference. What truly determines blood lactate concentration is the dynamic balance between the rate of production and the rate of clearance. As intensity rises, more fast-twitch muscle fibers are recruited, adrenaline increases, glycolytic flux rises, and lactate production speeds up; simultaneously, skeletal muscle, the heart, and the liver are also taking up lactate to use it. The concentration measured in the blood is the net result of these two opposing forces, not an “accumulated amount.”

1.2 Lactate Is Fuel, Not Garbage—The Lactate Shuttle

In modern exercise physiology, there is a crucial concept called the lactate shuttle: lactate is not a dead-end end product; it is an energy carrier that can be transported between cells, between organs, and even between different organelles within a cell.

Specifically, the lactate shuttle operates on at least several levels:

• Intracellular shuttle: Within the same muscle fiber, lactate produced in the cytoplasm can be transported near the mitochondria and oxidized for energy.
• Intercellular shuttle: Fast-twitch muscle fibers contracting at high intensity and relying mainly on glycolysis produce lactate, while neighboring slow-twitch fibers that rely on oxidative metabolism take it up and burn it as fuel.
• Interorgan shuttle: Lactate exported from working muscles can be taken up by the heart as fuel (the myocardium actually loves lactate), by the liver to be converted back into glucose via gluconeogenesis (the well-known Cori cycle), and even by the brain.

In other words, lactate is a “delivery system” the body uses to transport carbohydrate energy at high intensity. When you’re grinding out of the saddle on Wuling’s steep slopes, the lactate produced by your fast-twitch fibers might, a minute later, be burned in your heart or in another bundle of slow-twitch fibers. Calling it waste is rather unfair.

Furthermore, lactate is also regarded as a signaling molecule: it participates in regulating lipolysis, influences certain adaptive signaling pathways, and is one of the cues the body uses to sense metabolic stress. This is why in recent years many people no longer say “lactate tolerance training” but instead talk about “glycolytic flux training” or simply discuss intensity zones.

1.3 “Lactate Causes Next-Day Soreness”—Even More Wrong

This is probably the most widespread myth: after riding Fengguizui and back yesterday, your thighs are tight and sore today, so you say, “lactate hasn’t been flushed out yet.”

But the truth is: blood lactate concentration typically returns to near-resting levels within a timescale of tens of minutes after exercise. The delayed-onset muscle soreness (DOMS) that peaks the next day, or even two days later, is completely out of sync with that timeline. DOMS is generally thought to be related to microstructural damage to muscle fibers under eccentric contractions, the subsequent inflammatory and repair responses, and neural sensitization—especially pronounced after unfamiliar movements or heavy eccentric loading.

That’s why soreness is especially brutal after “downhill running,” “pushing hard in a race after a long layoff,” or “doing heavy back squats for the first time”—those are mechanical, repair-related processes, not chemical residue.

So: cool-downs, massage, stretching, and cold-water immersion might make you feel better through other mechanisms, but “helping you flush lactate” is not how they work. Lactate doesn’t need your help to be cleared; it gets used up on its own.

1.4 Acidosis and Lactate: Cause and Effect Have Been Confused

What about that “burning” feeling when you’re breathing hard and your legs are on fire? Muscle cells do become acidic (pH drops), and this metabolic acidosis does affect contractile function and sensation. But attributing it directly to “lactate” is chemically imprecise.

A more rigorous statement is this: at physiological pH, lactate exists almost entirely as lactate ions. What actually lowers pH is the accumulation of hydrogen ions, and the source of those hydrogen ions is mainly related to the high rate of ATP hydrolysis and the overall imbalance in energy metabolism—not “released by lactate.” On the contrary, the step that converts pyruvate into lactate actually consumes hydrogen ions, and when lactate is transported out of the cell, it typically carries hydrogen ions with it.

So a more accurate description is: lactate and acidosis are “two things that happen simultaneously,” because they share a common upstream cause (a large increase in glycolytic flux), but lactate is not the culprit behind acidosis; to some extent, it is actually part of the buffering mechanism.

This correction isn’t just academic pedantry; it affects how you understand training. If you think lactate is the enemy, you’ll want to “clear lactate.” If you understand lactate as merely an indicator, you’ll start asking the real question—at what intensity can my body still maintain metabolic stability?

And the answer to that question is the threshold.

---

2. LT1 and LT2: Two Thresholds, Two Different Things

If you undergo a standard incremental test in a laboratory (intensity increasing every 3 to 5 minutes, with a fingertip blood sample at the end of each stage) and plot intensity on the X-axis and blood lactate concentration on the Y-axis, you won’t get a straight line. You’ll get a curve that is flat at first, then rises gently, then climbs steeply.

There are two inflection points on this curve: LT1 and LT2.

2.1 LT1: The First Lactate Threshold (Aerobic Threshold)

LT1 is the intensity at which blood lactate begins to clearly deviate from the resting baseline and shows its first discernible rise.

Below LT1, your energy supply is dominated by fat oxidation, glycolytic flux is low, and lactate production and clearance are almost perfectly balanced, with concentration hugging the baseline. Past LT1, glycolysis begins to contribute meaningfully, lactate concentration creeps upward, but the body still has the capacity to handle it, so it stabilizes at a new plateau slightly above baseline.

Practical significance of LT1:

• This is the upper limit of intensity you can sustain “for a very long time.” All-day endurance rides, ultramarathon cruising pace, and the ceiling of recovery rides are all related to LT1.
• This is the zone where fat oxidation is relatively high and carbohydrate expenditure is relatively economical—critical for fuel management in long-distance events.
• In terms of breathing, it roughly corresponds to the first ventilatory threshold (VT1): breathing becomes deeper and faster, but you can still speak in complete sentences.
• This is the zone that most amateur cyclists ignore the most, yet should accumulate the most hours in.

A very realistic observation: many Taiwanese cyclists’ so-called “easy rides” are actually slightly above LT1. This kind of “not-easy-enough easy riding” accumulates fatigue without being intense enough to produce high-intensity adaptations—a classic gray zone.

2.2 LT2: The Second Lactate Threshold (Maximal Lactate Steady State, Critical Intensity)

LT2 is the highest intensity at which lactate production can still be matched by clearance. Just slightly above it, production will forever outpace clearance, and lactate concentration will no longer stabilize but will keep climbing until you are forced to slow down or stop.

This “highest sustainable intensity” goes by different names in different traditions:

• Described in terms of blood lactate: Maximal Lactate Steady State (MLSS)
• Described in terms of the power-duration relationship: Critical Power (CP) / Critical Speed (CS) for running
• Described in terms of ventilation: Second Ventilatory Threshold (VT2) / respiratory compensation point
• Described in training practice: FTP (more on why they aren’t exactly the same later)

Practical significance of LT2:

• It is the dividing line between “heavy” and “severe” exercise. Below LT2, oxygen uptake, heart rate, and muscle metabolites can reach a steady state; above LT2, these variables drift continuously, and exercise duration is mercilessly limited.
• It is one of the strongest single predictors of endurance performance. Of two people with the same VO₂max, the one with the higher LT2 will almost certainly be faster on a long climb.
• It is the core reference for pacing time trials, long climbs, and triathlon race segments.

2.3 Between the Two Thresholds: The “Middle Zone”

The region between LT1 and LT2 is where the so-called Tempo / Sweet Spot lives. Here, lactate concentration is above baseline but still stable, heart rate drifts slowly upward, and the subjective feeling is “somewhat hard but manageable.”

This zone isn’t a bad thing, but it has a dangerous characteristic: it’s so comfortable that you’ll unconsciously stay in it. It gives you the feeling of “I trained today,” but the cost is fatigue accumulation far exceeding the adaptive benefit it provides. This is the so-called “moderate-intensity trap.”

2.4 Correspondence Between the Three-Zone Model and the Five-Zone Model

Physiologically, the cleanest division is the three-zone model, because it is cut directly along the two real physiological inflection points, LT1 and LT2:

Zone	Boundaries	Physiological State	Subjective Feeling	Talk Test
Zone 1 (Moderate / Low Intensity)	Below LT1	Lactate near baseline, oxygen uptake stabilizes quickly	Easy, sustainable for hours	Can hold full conversation
Zone 2 (Heavy / Threshold Zone)	LT1 to LT2	Lactate elevated but stable, heart rate drifts slowly	Pressured but manageable	Can only speak short phrases
Zone 3 (Severe / High Intensity)	Above LT2	Lactate climbing continuously, oxygen uptake drifting upward	Clearly painful, feels like a countdown	Barely able to speak

Note that the naming here is easily confused: “Zone 2” in the three-zone model is the threshold zone, which is completely different from what people usually mean by “Zone 2 aerobic base riding” (the second zone in the five-zone model). This is one of the deepest sources of misunderstanding in the community—some people see “do more Zone 2” and go ride Z2 in the five-zone model, while others see a three-zone chart and think they should ride near threshold. The intensities are worlds apart. Whenever you see “Zone 2,” first ask which zone model is being used.

The approximate correspondence between common five-zone/six-zone training models and the two thresholds is as follows (this is only a conceptual mapping; different coaching systems use different cut points, and individual variation is large):

Five-Zone Model	Common Name	Relationship to LT1/LT2	Primary Training Purpose
Z1	Recovery	Clearly below LT1	Promote recovery, technique work, no fatigue generation
Z2	Aerobic Endurance / Base	Near but not exceeding LT1	Mitochondrial and capillary adaptations, fat oxidation capacity, durability
Z3	Tempo	Between LT1 and LT2, lower portion	Carbohydrate metabolism efficiency, muscular endurance, long-climb rhythm
Z4	Threshold / Upper Sweet Spot to Threshold	Close to LT2	Raise MLSS, extend sustainable duration
Z5 and above	VO₂max / Anaerobic / Sprint	Clearly above LT2	Maximal oxygen uptake, anaerobic capacity, neuromuscular

The point isn’t to memorize this table; it’s to understand that the meaning of all training zones derives from their position relative to LT1 and LT2. If you don’t know where your two thresholds are, the numbers on a zone chart are just decoration.

---

3. The Battle of the Terms: What’s the Difference Between FTP, MLSS, CP, OBLA, and AT

This is where many people get truly stuck. Below, I’ll first clarify the origin of each term, then provide a comparison table.

3.1 Anaerobic Threshold

The oldest term, and the one most deserving of retirement. It presupposes that “beyond a certain intensity, the body goes anaerobic,” but we already know this premise is wrong: there is no switch that suddenly turns off aerobic metabolism. Oxidative metabolism continues operating at full capacity even at very high intensities. This term now mostly appears only in old textbooks, gym fitness reports, or certain running watch interfaces. When you see it, you can mentally translate it as “probably referring to LT2,” but don’t use it as a framework for thinking.

3.2 OBLA (Onset of Blood Lactate Accumulation)

This refers to the intensity corresponding to a fixed blood lactate concentration cutoff. Traditionally, approximately 4 mmol/L is used as a reference, and approximately 2 mmol/L is often used as a reference point near LT1.

A very cautious note is needed here: these fixed cutoffs are convenient tools designed to give different laboratories a comparable operational definition. Individual variation is large, and they should not be treated as absolute standards. Some people’s true MLSS corresponds to a blood lactate concentration clearly below 4; others clearly above 4. The same person, in a glycogen-loaded versus glycogen-depleted state, will show different lactate values at the same intensity. Using a fixed number to define a highly individualized physiological inflection point has inherent limitations.

3.3 MLSS (Maximal Lactate Steady State)

Conceptually, this is the closest to the “true LT2,” but operationally it is the most troublesome: the orthodox method involves performing long constant-power tests at different fixed intensities (typically on the order of nearly half an hour each), drawing blood every few minutes, observing whether lactate concentration remains stable or keeps rising in the latter half, and then bracketing out the MLSS by trial and error.

This means spanning several days and multiple tests to pin down a single number. Accurate, but completely impractical for amateur cyclists.

3.4 CP (Critical Power)

Derived from a mathematical model: the time you can sustain a given power has a hyperbolic relationship with the power level. This curve has an asymptote, which is CP; the area enclosed between the curve and the asymptote represents the finite amount of work you can do above CP, called W′ (W prime).

In practice, performing two to three all-out tests of different durations (e.g., a short one of a few minutes and a long one of ten-plus minutes) allows you to fit CP and W′. Conceptually, CP is very close to MLSS, and the two usually fall in a similar range, but the values are not identical, and they are affected by test duration choices, daily form, and pacing strategy.

The additional value of the CP model lies in W′: it lets you understand “why someone with a modest threshold can still attack so effectively”—that’s a large W′. When you repeatedly accelerate on the short steep slopes of Beiyi or Fengguizui, you’re spending your W′.

3.5 FTP (Functional Threshold Power)

FTP grew out of training practice. The most common definition is “the highest average power you can sustain for approximately one hour,” and a convenient method was developed to estimate it using a 20-minute test multiplied by a discount factor.

FTP’s strengths are that it is operable, repeatable, and can be directly used to structure training plans. Its problems are:

1. “Highest power for one hour” does not necessarily coincide with MLSS. Some people can sustain above MLSS for an hour; some cannot last an hour at MLSS.
2. The 20-minute times discount factor is an empirical simplification, and its accuracy varies by endurance profile. People with a large W′ and good explosiveness tend to be overestimated; purely aerobic endurance types may be underestimated.
3. FTP is a “performance metric,” not a directly measured physiological inflection point. It is affected by mood that day, warm-up quality, route selection, and whether someone is pacing you.

The healthiest attitude is to treat FTP as a practical proxy for LT2, not as LT2 itself. It’s a useful training anchor, not a truth on a medical report.

3.6 A Summary Table

Term	Essence	Corresponds To	How to Obtain	Main Limitations
LT1	Intensity where blood lactate first clearly departs from baseline	Aerobic threshold, VT1	Laboratory incremental test; practical estimation via talk test / nasal breathing / heart rate drift	Inflection point interpretation is subjective; different methods yield different results
LT2	Highest balance point between lactate production and clearance	MLSS, CP, VT2, colloquially “threshold”	Laboratory test or multiple constant-power tests	Orthodox methods are time-consuming and costly
MLSS	Highest fixed intensity at which lactate steady state can be maintained	Nearly identical to LT2	Multiple days of long constant-power tests with repeated blood sampling	Nearly infeasible for amateurs
CP	Asymptote of the power-duration hyperbola	Close to LT2, with slight differences	Fit from 2–3 all-out tests of different durations	Affected by test duration and pacing strategy
FTP	Highest power sustainable for approximately one hour	Practical proxy for LT2	20-minute test with discount factor, Ramp test estimation, or long segment field test	A performance metric, not a physiological measurement; estimation methods have systematic bias
OBLA	Intensity corresponding to a fixed blood lactate cutoff	Often used as a rough estimate of LT2	Blood lactate test	Fixed numbers ignore individual variation; for reference only
Anaerobic Threshold	Outdated term	Usually refers to LT2	—	The name itself is based on a false premise; recommended for retirement

---

4. How to Estimate: From the Laboratory to the Riverside Bike Path

4.1 Laboratory Blood Lactate Incremental Test (Principles)

The most direct approach is to undergo an incremental test at an exercise physiology laboratory or a facility offering such services: start at a low intensity, increase every 3 to 5 minutes, take a fingertip blood sample at the end of each stage, and continue until exhaustion or a preset endpoint. With gas analysis, you can also obtain ventilatory thresholds and VO₂max simultaneously.

Several key details that affect results—worth asking about in advance if you’re going to do one:

• Stage duration: If too short (e.g., 1-minute stages), blood lactate doesn’t have time to equilibrate, the curve gets flattened, and thresholds tend to be overestimated.
• Training and diet the day before: Glycogen status directly affects lactate production. If you did heavy high-intensity work or deliberately went low-carb before the test, the numbers aren’t comparable.
• Interpretation method: There are several methods for determining LT1 (visual inflection, baseline plus fixed increment, piecewise linear regression, etc.), and different methods give different answers. Ask them to tell you which method they use, and use the same method every time, or there’s no tracking value.
• Test modality: A threshold measured on a bike cannot be directly applied to running, and vice versa. Specificity matters.

4.2 Breathing and Talk Test (Estimating LT1, Cheapest and Most Durable)

Near LT1, there is a fairly reliable behavioral indicator: breathing rhythm begins to change, but you can still speak in complete sentences.

Practical approach:

1. Ride at a fixed intensity (trainer or a flat, steady section), starting on the easier side, and increase slightly every few minutes.
2. At each stage, read a passage aloud (e.g., recite a longer sentence, or tell a riding buddy a complete narrative).
3. Find the critical point where you “can still finish the sentence, but you’re already having to break for breath”—that roughly marks the LT1 zone.
4. Above that, when you can only gasp out three to five words before needing to inhale, you’ve entered the region above LT1.

This method looks crude, but its advantage is that it’s unaffected by weather, dehydration, heart rate drift, or power meter calibration, and anyone can use it at any time. Many experienced coaches treat it as the final gatekeeper: no matter what the power meter says, if an athlete can’t speak in complete sentences on a day that’s supposed to be an easy ride, then today was ridden too hard.

4.3 Nasal Breathing Test (Another Rough Screen for LT1)

Some people use “the highest intensity you can maintain while breathing only through your nose” to roughly estimate LT1. The principle is that once ventilatory demand rises to a certain level, the airflow resistance of the nasal passages forces you to open your mouth.

This method has several practical limitations: people with a deviated nasal septum, allergic rhinitis, or a cold with nasal congestion will get severely depressed results. In Taiwan’s humid, allergen-rich environment, this situation is not uncommon. It can serve as a supplementary self-awareness tool, but it’s not recommended as the sole basis. On days with poor air quality, deliberately practicing nasal breathing is also inadvisable.

4.4 Heart Rate Drift / Decoupling (A Field Test for Estimating LT1)

This is the most practical self-test for LT1 for people with a power meter or running power/pace data. The principle is: at intensities below LT1, the relationship between heart rate and power output should be relatively stable; once you exceed LT1, heart rate will keep climbing over time while power stays constant—the two “decouple.”

Procedure:

1. After a full warm-up, choose a section where you can maintain steady output for at least 60 minutes, or use a trainer.
2. Hold a fixed power at your guessed LT1 intensity (or slightly below), avoiding large surges.
3. Afterward, split the 60 minutes into first and second halves, and calculate “average power ÷ average heart rate” for each.
4. Compare the magnitude of change in the second half relative to the first. A common practical reference: drift within single-digit percentages suggests the intensity is still roughly below LT1; clearly large drift means you’ve exceeded it. Specific thresholds vary slightly among coaching systems; what matters is your own long-term trend, not comparison with others.

There are many confounding factors to watch: heat, dehydration, caffeine, sleep deprivation, a heavy session the day before, and even insufficient fueling will all increase drift. In Taiwan’s summer, this test almost has to be done in the early morning or on a trainer; otherwise, heat stress will completely distort the results (more on this in Section 6).

4.5 The 20-Minute Test (Estimating FTP/LT2)

The most popular method, roughly as follows:

1. Full warm-up (including a few short accelerations to wake up the system).
2. A 5-minute all-out effort, used to burn off some of the “fresh anaerobic capacity” (some versions include this, some don’t).
3. After a short recovery, perform a 20-minute all-out average power test.
4. Multiply the 20-minute average power by a discount factor to obtain an FTP estimate.

Strengths: low barrier to entry, repeatable, and backed by a large body of reference experience.
Weaknesses and pitfalls:

• Pacing ability determines the result. Almost everyone doing it for the first time goes out too hard in the first 5 minutes, blows up in the latter half, and gets an underestimated number. It’s advisable to do it at least twice before trusting the result.
• The discount factor is an empirical value, not a constant. Explosive athletes with a large W′ will be overestimated using the same factor.
• Psychological and environmental influences are large. Results on a trainer and on an outdoor long climb often differ.
• It’s a hard load on the body. It is itself a heavy training session and cannot be treated as a casual activity.

4.6 Ramp Test

Starting from a low intensity, power increases at a fixed rate (e.g., increasing by a step every minute) until you can no longer turn the pedals, then the average power of the final segment is multiplied by a certain ratio to estimate the threshold.

Strengths: short, concentrated suffering, requires almost no pacing skill, suitable for beginners.
Weaknesses: it actually measures closer to the edge of “maximal aerobic capacity,” and its threshold estimate is heavily influenced by individual endurance profile—people with strong anaerobic capacity will be overestimated, while purely aerobic types will be underestimated. Using a Ramp test to track trends for the same person is reasonable; using it to compare FTP with others is meaningless.

4.7 CP Test (Two or Three Segments)

Perform two to three all-out tests of different durations (e.g., one short, one long), on separate days to ensure fresh form, then fit the power-duration model to derive CP and W′.

Strengths: you get both the threshold and the anaerobic reserve in one go, which is very useful for pacing strategy (e.g., you know roughly how much “budget” you have to spend above CP).
Weaknesses: multiple all-out tests are required, and the total load is considerable; pacing errors in the short segment can severely distort the fitted results.

4.8 Comparison Table of Test Methods

Method	Primarily Estimates	Equipment Needed	Physical Load	Repeatability	Best For
Laboratory blood lactate incremental test	LT1 + LT2	Professional equipment	Moderate to high	High (same protocol)	Serious athletes who want both thresholds clarified at once
Talk test	LT1	None	Very low	Moderate	Everyone, especially beginners
Nasal breathing	LT1 (rough screen)	None	Very low	Low	Supplementary tool for those with clear nasal passages
60-minute heart rate drift	LT1	Power meter + heart rate strap	Moderate	Moderate to high (requires controlled environment)	Those with equipment who want to confirm base-ride intensity
20-minute test	FTP (LT2 proxy)	Power meter	High	Moderate (requires pacing practice)	Those with some training foundation
Ramp test	Rough threshold estimate	Power meter, trainer preferred	High but short	High	Beginners, those wanting regular trend tracking
CP two- or three-segment test	CP + W′	Power meter	High (spread over multiple days)	Moderate	Advanced athletes needing a pacing model

4.9 A Practical Self-Testing Protocol You Can Run (Cyclist Edition)

If you have a power meter and heart rate strap and want to get a rough picture of both LT1 and LT2 within one to two weeks, here’s one way to arrange it. This is only an example; individual variation is large, so adjust according to your own condition and progress gradually.

Day 1: LT1 detection (heart rate drift + talk test)

• Early morning or on a trainer, cool room temperature, well fueled.
• After a 15-minute warm-up, hold a fixed power at your guessed “easy but slightly up” intensity for 60 minutes.
• Every 15 minutes, do a talk test (recite a complete passage).
• Afterward, calculate the power/heart rate ratio change between the first and second halves.
• If drift is small and you could speak in complete sentences throughout → next time, nudge the intensity up slightly and test again; if drift is obvious or you couldn’t finish sentences in the latter half → this intensity is already above LT1.

Days 2–3: Easy rides or rest only.

Day 4: LT2 estimation (20-minute test or Ramp test, choose one)

• Choose a safe section with a steady grade, minimal traffic, and no need to stop, or use a trainer directly. A trainer or closed course is strongly recommended; avoid all-out testing on open roads.
• Full warm-up, including 3 progressive 30-second accelerations.
• Execute the test, pacing conservatively in the first half and pressing harder in the second.
• Be sure to do a 10–15 minute cool-down afterward.

Days 5–7: Recovery, low intensity only.

Week 2: Use the estimated numbers for a few actual sessions, then calibrate.

• If long intervals that “should be below LT2” blow up no matter what → the estimate is too high.
• If you can easily exceed the estimate and hold on for a long time → the estimate is too low.
• Actual training response is the final judge; numbers are just a starting point.

4.10 Safety Reminders (Please Read Carefully)

• The 20-minute test, Ramp test, and CP test are all maximal or near-maximal efforts and represent a clear stress on the cardiovascular system.
• If you have a history of cardiovascular disease, a family history of sudden death, poorly controlled hypertension, chest tightness or pain, unexplained dizziness, arrhythmia, or have been sedentary for a long time and suddenly want to start, consult a physician before deciding whether to undergo high-intensity testing.
• If during a test you experience chest pain, chest tightness, noticeable palpitations, dizziness, darkening vision, cold sweats, nausea, or unusual shortness of breath, stop immediately, cool down, and seek medical attention if necessary. Don’t “push through and see.”
• Do not perform maximal effort tests while ill, after a fever, or during discomfort following vaccination.
• For outdoor testing, never perform all-out sprints or time-trial racing on open roads. Taiwan’s mountain roads often have falling rocks, gravel, oncoming traffic, tour buses, scooters, and pedestrians; popular routes like Beiyi and Fengguizui also see fast descending vehicles. You can do steady-intensity testing on a climb, but stay in your lane, watch the road, avoid peak hours, and slow down on descents.
• This article provides general training knowledge and cannot replace individual assessment by sports medicine, cardiology, or exercise physiology professionals.

---

5. Common Mistakes

5.1 Treating FTP as the Holy Grail

The most common and most damaging mistake. FTP is only a proxy metric; it cannot tell you how thick your aerobic base is, how much you have left after four hours, how large your W′ is, or how well you tolerate fatigue.

Two cyclists with the same FTP—one can hold a steady output all the way up Wuling, the other blows up halfway up the mountain—the difference is often in durability, meaning “after accumulating several hours, how much of your threshold is left.” The FTP number reveals none of this.

What’s more worth tracking: how much intensity you can still hold in a fatigued state, how much your power declines in the latter half of a long ride, and how your heart rate and perceived effort change at the same intensity.

5.2 Testing Every Day, Every Week

Thresholds are the result of long-term adaptation; they won’t rise noticeably within seven days just because you trained harder this week. Frequent testing accomplishes only three things: generating a lot of fatigue, disrupting training rhythm, and making you neurotic over noise from daily fluctuations (sleep, hydration, body temperature, caffeine, psychological state).

A reasonable cadence is to retest on a scale of weeks to months, or at key transition points in a training cycle. In between, use actual performance in workouts (e.g., whether a certain set of intervals feels easier than last month) as an indirect indicator.

5.3 Too Much Sweet Spot

Sweet Spot is popular because it’s “efficient”: good return on time investment, more comfortable than threshold workouts, and more tangible than easy riding. But its problem is precisely that it’s neither easy enough nor hard enough.

If four out of five weekly sessions fall between LT1 and LT2, you’ll get:

• Chronic fatigue accumulation, with recovery days never sufficient.
• Insufficient low-intensity volume, compressing long-term mitochondrial and capillary adaptations.
• Declining high-intensity quality, because you’re always doing intervals with residual fatigue, so intensity can’t go up.

This isn’t to say Sweet Spot is unusable; it should be one tool in the toolbox, not the staple food. Especially on weekends when time is plentiful, keeping long rides below LT1 and simply accumulating hours is an approach whose long-term benefits are often severely underestimated.

5.4 Ignoring LT1, Insufficient Aerobic Base

A common profile among Taiwanese cyclists: FTP isn’t low, short climbs are fierce, but anything over three hours and they completely fall apart. This is usually not a willpower issue; it’s insufficient low-intensity base volume.

The adaptations associated with LT1 (mitochondrial density, capillarization, fat oxidation capacity, muscular lactate clearance capacity) require large amounts of time to build, and they must be built at a low enough intensity to avoid paying an excessive fatigue cost. This is the only correct version of the old saying “ride slow to get fast.”

In practice, the most effective way to raise LT1 is usually not some special workout, but simply: make easy rides truly easy, then extend the duration.

5.5 Using Someone Else’s Zone Chart

“Coach says Z2 is 56–75% of FTP”—percentage tables like this exist to give people who haven’t measured their thresholds a starting point; they are not physiological facts. In reality, the percentage of FTP at which each person’s LT1 falls varies widely; some people’s LT1 is clearly above the upper edge of Z2 given by a chart, and some are clearly below.

The most common consequence of riding according to someone else’s chart is accumulating hours at intensities above LT1 while thinking it’s “aerobic base riding”—training yourself into a state of fatigue. Using the talk test or heart rate drift to calibrate your own Z2 upper edge is far more useful than memorizing percentages.

5.6 Using Heart Rate as the Only Basis

Heart rate is valuable information, but it responds slowly and is heavily disturbed: heat, dehydration, sleep, caffeine, psychological stress, and the early stages of a cold can all shift it. In the first 1 to 2 minutes of an interval, heart rate hasn’t even caught up with your actual output.

A better approach: use power or pace to control output, use heart rate to observe the body’s response to that output, and use RPE (rating of perceived exertion) as the final arbiter. When the three disagree, the body is usually telling you something the numbers aren’t.

5.7 Testing Only on the Trainer, or Only Outdoors

Power on a trainer and outdoors often differs systematically (cooling, posture, inertia, psychology). If you take an FTP measured outdoors and apply it to trainer workouts, you may fail to complete every session.

Principle: keep the testing environment as consistent as possible with the training environment, or record two separate sets of numbers.

5.8 Ignoring That “Today’s Threshold Isn’t Last Month’s Threshold”

Thresholds fluctuate with training status, fatigue, season, body weight, and illness. A single test gives you “an estimate at that time,” not a permanent identity card. When workouts suddenly become abnormally hard or abnormally easy, first question the numbers; don’t grit your teeth and push through.

---

6. Taiwan-Specific Context: What to Test Where, and the Summer Problem

6.1 What Each Route Is Suitable For

Wuling (Provincial Highway 14A)—Long-duration tolerance and durability; not suitable for testing the threshold itself

On a multi-hour continuous climb like Wuling, the most valuable information isn’t “what’s my threshold” but “how much do I have left in the third and fourth hours.” Altitude progressively affects oxygen uptake and heart rate, the grade varies greatly, and fueling and thermoregulation are all variables. Treat it as a field test for durability, not a threshold test venue.

Things to observe on Wuling: how much power drops at the same heart rate in the latter stages, whether your fueling strategy lets you maintain stability in the second half, and how your breathing and sensation change at altitude.

Fengguizui—Short-duration all-out testing (CP short segment, Ramp alternative)

Routes like Fengguizui, where “one climb doesn’t take too long and the grade is relatively continuous,” are suitable for short-duration all-out tests and for repeated-climb intervals. But pay attention to traffic and descent safety: this is a popular route for Taipei cyclists, crowded on weekends, so avoid peak hours and watch for riders going up and down.

Beiyi Highway—Rhythm and handling variability

Beiyi’s rolling grades and curves make it hard to maintain steady power, so it is not suitable for tests requiring constant output. Instead, it’s an excellent training ground for “variable-intensity tolerance”: practice keeping your average output below LT2 amid fluctuations and avoiding overspending W′ on every small climb. This ability is extremely valuable in real races. Also note: Beiyi has complex traffic and plenty of large vehicles; ride conservatively.

Riverside Bike Paths—The Best Venue for LT1 Testing

Flat, allowing long periods of steady output, and easy to stop at any time, riverside bike paths are ideal for the 60-minute heart rate drift test and long accumulation rides below LT1. But be aware: riverside paths have pedestrians, dogs, children, riders coming the wrong way, and underpass ramps—treat it as a venue for steady output, not racing. When it’s windy (especially the winter northeast monsoon), the power/speed relationship differs greatly between headwind and tailwind sections; use power rather than speed to control intensity.

Datun Mountain, Balaka, Yangjin P-Character Road, County Highway 106—Segmented intervals and long-climb rhythm

These routes are intermediate in length, suitable for long intervals near LT2. Again, be mindful of rapidly changing mountain weather, slippery descents, falling rocks, and gravel.

6.2 How Summer Heat and Humidity Interfere with Threshold Testing

Doing threshold tests in Taiwan’s summer requires special care.

How heat affects the numbers:

1. Heart rate is elevated: At the same power, heart rate rises significantly in high heat because the body must send large amounts of blood to the skin for cooling. This is called cardiovascular drift. The result is—you think you’ve exceeded LT1, but it’s actually the heat.
2. The heart rate drift test is completely distorted: A 60-minute decoupling test on a hot afternoon will almost certainly “fail,” because all the drift comes from heat and dehydration, not intensity.
3. Dehydration amplifies everything: Plasma volume drops → stroke volume drops → heart rate rises further to compensate. This is a vicious cycle.
4. Power output decreases: At the same perceived effort, you can typically output less power in hot, humid conditions than in cool conditions. An FTP measured in summer used to plan winter workouts may be too low; conversely, you might plan workouts you can’t complete.
5. High humidity prevents sweat from evaporating: This is the most vicious aspect of Taiwan’s summer—humidity. Sweat runs off but doesn’t carry heat away, so it’s wasted. This is why the same 32°C feels completely different in Taipei than in a dry region.

Practical recommendations:

• Schedule tests in the early morning or use an indoor trainer with good fans. Indoors without a strong fan, cooling conditions can be worse than outdoors.
• In summer, the reliability of using heart rate to define training zones drops significantly; the weight given to power and RPE should increase.
• Record environmental conditions (time, temperature, humidity, wind) so tests from different periods are comparable.
• Accept seasonal variation: summer threshold numbers are usually lower than in the cool season; that doesn’t mean you’ve regressed. Consider establishing “summer edition” and “cool season edition” training zones.
• Heat injury warning signs: headache, nausea, goosebumps, cessation of sweating, confusion, loss of coordination—if any of these appear, stop immediately, move to shade, hydrate, cool down, and seek medical attention if necessary. This matters more than any test data.
• On days of heavy rain or poor air quality: when visibility is low, roads are slippery, or particulate matter is high, move indoors or reschedule. No test is worth that risk.

6.3 Winter Northeast Monsoon

In winter along the north coast or riverside paths, wind is the biggest variable. Into a headwind, you might ride at LT2 power and still be slow; with a tailwind, an easy ride can be very fast. This is precisely the scenario where a power meter is most valuable: execute workouts using power rather than speed or heart rate. Without a power meter, RPE and the talk test are far more reliable than watching speed.

---

7. Actually Putting the Two Thresholds to Use in Training

7.1 General Principles for Training Intensity Distribution

A fairly consensus observation in the endurance world is: the vast majority of training time for high-level endurance athletes falls below LT1, with high intensity occupying only a small portion, and the middle zone being the least. This distribution is often called polarized training; another common pattern is pyramidal distribution (most low intensity, less moderate, least high).

It must be stated clearly: these are population-level observational principles, not prescriptions everyone must copy. An amateur with limited time (e.g., only 5 hours per week) and someone training 25 hours per week will not have the same optimal distribution. Individual variation is large; progress gradually and adjust according to your own responses.

But one principle applies almost universally: easy days should be truly easy, and hard days should be truly hard. Do both ends well, and the middle will take care of itself.

7.2 Means to Raise LT1

• Long-duration, low-intensity steady riding (truly below LT1).
• Accumulate weekly hours rather than increasing the intensity of each session.
• Patience: this is a project measured in months and seasons.
• If time is extremely limited, you can insert a few tempo segments into a long ride, but don’t let the whole ride become Tempo.

7.3 Means to Raise LT2

• Long intervals near LT2 (e.g., several segments of ten-plus minutes with full recovery between).
• Intervals slightly above LT2 (shorter duration, longer recovery), used to push the ceiling up from above.
• VO₂max workouts: raising the upper limit usually also gives LT2 more room.
• Note: these are all high-load workouts. Keep the number of high-intensity sessions per week in check, and ensure adequate sleep and nutritional support.

7.4 When to Retest

• At the end of a training cycle (typically every few weeks to a few months).
• When workouts become clearly too easy or too hard.
• When precise pacing is needed before a race season.
• Do not test at a fatigue peak, after sleep deprivation, after illness, or immediately after a race.

---

8. FAQ

Q: I don’t have a power meter, only a heart rate strap. Can I test my thresholds?
You can estimate. Use the talk test to find LT1, and use “the highest steady heart rate you can sustain for roughly half an hour to an hour” to roughly estimate the heart rate zone near LT2. But remember that heart rate is affected by heat, dehydration, and fatigue, and it responds with a delay during intervals, so be sure to combine it with RPE.

Q: Are the threshold heart rates for running and cycling the same?
Usually not; running threshold heart rate tends to be somewhat higher than cycling (due to different posture and muscle usage). Don’t directly apply zones measured on the bike to running. Triathletes should establish two separate sets (and a third pace set for swimming).

Q: Is a blood lactate meter worth buying?
You can buy one, but understand its limitations: a single reading means little; what matters is the trend under the same protocol and same conditions. Blood sampling timing, whether to wipe away the first drop, finger temperature, and that day’s glycogen status all affect readings. If you’re not planning to establish a standardized process, your money might be better spent elsewhere.

Q: Why is my threshold lower today than last month? Have I regressed?
Not necessarily. Fatigue, sleep, weather, glycogen status, and psychological state all cause single-session fluctuations. Look at trends, not single points. If it keeps declining across several tests, accompanied by worsening sleep, abnormal resting heart rate, and declining motivation, the issue to consider is overtraining and insufficient recovery, not training more.

Q: So which Zone 2 is the real Zone 2?
Ask which zone model is being used. If the person means “can talk, can ride for a long time, burns fat,” that’s Z2 in the five-zone model, roughly corresponding to below LT1; if they mean “threshold zone, very hard,” that’s Zone 2 in the three-zone model.

---

9. Key Takeaways

1. Lactate is not waste; it’s an energy carrier and signaling molecule, constantly being produced and utilized.
2. Lactate does not cause next-day soreness; DOMS is related to microdamage from eccentric loading and the subsequent repair response.
3. Lactate is not the culprit behind acidosis; the two merely share a common upstream cause, and lactate even participates in buffering.
4. Blood lactate concentration is the net result of production and clearance, not an accumulated amount.
5. LT1 is the upper limit of “can do it for a long time”; LT2 is the upper limit of “can still maintain a steady state.” Their meanings are completely different.
6. Zone 2 in the three-zone model ≠ Z2 in the five-zone model; when you see the term, first ask which model.
7. FTP, CP, MLSS, and OBLA are not synonyms; FTP is a practical proxy for LT2, not a physiological measurement.
8. The traditional 2 and 4 mmol/L values are merely operational reference cutoffs; individual variation is large, and they are not absolute standards.
9. LT1 is the most overlooked, yet it is the foundation of long-distance performance.
10. Sweet Spot is a tool, not the staple food.
11. Summer heat and humidity severely distort heart rate and threshold testing; test in the early morning or indoors with a fan.
12. High-intensity testing carries risk; if you have cardiovascular concerns, see a doctor first, and stop immediately if you experience chest tightness, chest pain, or dizziness.

---

10. Action Checklist

Things you can do this week:

• [ ] Do the talk test on your next easy ride and honestly check whether your “easy ride” is truly easy.
• [ ] Check where your current training zones came from: measured? percentage chart? someone else’s?
• [ ] Record environmental conditions (temperature, humidity, time) for your last three long rides and see whether heart rate differences are explained by weather.

Things you can do in the next month:

• [ ] Schedule one 60-minute heart rate drift test (early morning or indoors) to estimate your LT1 upper edge.
• [ ] On a well-rested, non-fatigued week, schedule one 20-minute test or Ramp test to estimate LT2. Confirm you have no physical discomfort before testing; if you have cardiovascular concerns, see a doctor first.
• [ ] Rebuild your training zones using the estimated numbers, and clearly keep long rides below LT1.
• [ ] Create a simple test log: date, method, environment, result, and how you felt that day.

Things you can do in the next season:

• [ ] Treat low-intensity volume as one of your primary progress indicators, not just FTP.
• [ ] Observe durability: in the third and fourth hours of a long ride, how much does power drop at the same heart rate?
• [ ] At the end of the next cycle, retest using the same method and the same environment, and compare trends.

---

Disclaimer: This article provides general exercise physiology and training knowledge. Individual variation is large, and all training recommendations should be progressed gradually and adjusted according to your own condition. This article cannot replace individual assessment by a physician, physical therapist, or exercise physiology professional. If you have cardiovascular disease, a chronic condition, are taking medication, or have been sedentary for a long time, consult a medical professional before beginning high-intensity training or undergoing maximal effort testing. When riding outdoors, obey traffic rules and pay attention to road and weather conditions. This site does not encourage racing on open roads.

Related Reading

• Lactate Threshold vs FTP: A Complete Analysis of the Two Most Confused Training Metrics
• The Truth About Lactate Threshold and Anaerobic Threshold: Lactate Is Not Waste but Fuel
• Lactate Threshold Fully Explained: LT1, LT2, and the Anchors of Training Zones
• The Science of Lactate Threshold Training: Physiological Mechanisms and Training Applications of LT1 and LT2