What Exactly Is a Threshold? Definitions, Relationships, and Practical Trade-offs of Ventilatory, Lactate, and Power Thresholds

Starting from a Conversation After a Ride

A few years ago, on a Sunday morning, I was cruising down Fengzuiwei on Yangmingshan with a student, Xiao Chen, who was preparing to take on the Westbound Wuling challenge. During a break, he scrolled through his phone and asked me: “Coach, my power meter says my FTP is 240 watts, but last time I went to the lab, the report said my lactate threshold is around 220 watts. Then my watch popped up with a ‘ventilatory threshold heart rate of 162 bpm’—which of these three is the real one? Which should I train by?”

I smiled. In my 15 years of coaching, I’ve probably been asked this question a hundred times. It sounds like nitpicking over numbers, but underneath it lies one of the most confusing core concepts in endurance sports physiology—and one that commercial marketing has often oversimplified to the point of distortion: the threshold.

The root of the problem is this: a “threshold” is not a single thing; it’s an entire family of concepts. When we say “you’re below threshold” or “this is a threshold workout,” many people assume we’re talking about the same line. But ventilatory threshold, lactate threshold, and functional threshold power are three completely different measurement systems—breathing, blood, and power—all trying to approximate the same physiological phenomenon. They are highly correlated with each other, but they don’t overlap perfectly, and each has its own assumptions and errors.

In this article, I want to lay this out clearly once and for all. Not to turn you into an exercise physiologist, but so that the next time you see your test report or a number on your watch, you know what that line represents, whether it’s trustworthy, and how to use it to plan your training. I’ll try to use the tone I use with my athletes, weave in some real-world scenarios, and include tables you can follow directly.

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Why the Body Has “Thresholds” at All

From Fully Aerobic to Starting to Sound the Alarm

Let’s start with the most fundamental concept. When you ride or run, your muscles need energy (ATP). At low intensity, your body relies almost entirely on aerobic metabolism—with plenty of oxygen, fat and carbohydrates are burned slowly and cleanly, with few byproducts. You can chat while riding and keep going for hours.

But when you push the intensity up, the aerobic system starts to fall behind demand, and the body increasingly relies on glycolytic metabolism to make up the energy shortfall. This process produces lactate (more precisely, lactate salt, or lactate) and hydrogen ions, challenging the acid-base balance in your muscles and blood.

There’s a huge common misconception to clear up first: lactate itself is not a “fatigue toxin,” nor is it the culprit behind next-day soreness. Lactate is actually a fuel that can be reused—your heart, slow-twitch muscle fibers, and even your brain will burn it. What really makes you “blow up” is more about the accompanying accumulation of hydrogen ions, the shift in the metabolic environment, and overall regulation. So we measure blood lactate not because lactate is toxic, but because blood lactate concentration is a very convenient “metabolic stress indicator”—it’s like the tachometer on a dashboard, telling us how much the body is currently relying on anaerobic pathways.

Two Inflection Points, Not One Line

When exercise physiologists look at this curve of “the higher the intensity, the greater the metabolic stress,” they find it doesn’t rise smoothly but has two distinct inflection points:

• First inflection point (lower intensity): Blood lactate starts to creep up slightly from resting levels, and breathing begins to quicken a bit. This roughly corresponds to the zone where you go from “easy to slightly breathless, but still able to speak in short sentences.”
• Second inflection point (higher intensity): Lactate starts to spike rapidly and uncontrollably, breathing becomes deep and urgent, you can only utter single words, and you can’t sustain it for long. This line roughly represents the “ceiling” you can maintain for an extended period.

These two inflection points are what all threshold concepts are trying to capture. The trouble is that different measurement methods (looking at breathing, blood, or power) define and name these two points differently, and so the terminology explodes. Let’s break them down one by one.

Here’s another concept that’s often overlooked but crucial for planning training: these two inflection points divide your intensity spectrum into three metabolic zones—the “moderate zone” below the first inflection point (sustainable for a very long time, primarily fat-fueled), the “heavy zone” between the two inflection points (lactate rises but can still be stabilized for a while), and the “severe zone” above the second inflection point (lactate keeps rising uncontrollably, unsustainable for long). You’ll notice that the five training zones mentioned earlier are essentially just a finer subdivision of these three metabolic zones. Understanding the existence of the “three zones” matters more than memorizing the percentages of the five zones, because it tells you: what really determines training effect is which metabolic zone your effort falls into, not which color pops up on your watch. This is also why, given the same workout plan, some people improve while others stay stagnant—the difference often lies in whether they actually hold the boundaries of their zones.

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Definitions of the Three Major Threshold Types

1. Ventilatory Threshold (VT)—Looking at Your Breathing

The ventilatory threshold is found through respiratory gas analysis (wearing a mask that measures how much oxygen you inhale and how much carbon dioxide you exhale). It’s usually divided into two:

• VT1 (first ventilatory threshold): The first point where ventilation starts to rise disproportionately relative to oxygen consumption. At this point, the body begins to need to expel more carbon dioxide. VT1 roughly corresponds to where blood lactate just starts to climb.
• VT2 (second ventilatory threshold): Ventilation surges again as the body hyperventilates to buffer the increasing acid. VT2 roughly corresponds to the line where lactate rises rapidly and uncontrollably.

The advantage of the ventilatory threshold is that it’s non-invasive (no finger pricks or blood draws), and it can capture both points in a single incremental exercise test. Research has also confirmed that the workload at VT1 correlates fairly strongly with the workload at which blood lactate begins to rise above resting values. The downside is that it requires a gas analyzer, and interpretation has some subjectivity—different readers may place the points at slightly different locations.

2. Lactate Threshold (LT)—Finger Prick to Check Blood

The lactate threshold involves directly drawing capillary blood from the fingertip or earlobe, measuring blood lactate concentration at different intensities, plotting the curve, and then finding the inflection. Because it directly measures a metabolic byproduct, many regard it as a “harder” physiological metric. But this is also the worst-hit area for terminology confusion, because “lactate threshold” is further subdivided into several definitions:

• LT1 (first lactate threshold / aerobic threshold): The point where blood lactate begins to rise clearly above the resting baseline, usually corresponding to VT1.
• LT2 (second lactate threshold / anaerobic threshold): The point where lactate begins to rise steeply—this is what many people mean by “lactate threshold.”
• Fixed concentration method: Historically, Mader et al. proposed in 1976 using a fixed blood lactate concentration of 4 mmol/L as an estimate of the threshold—this is the “4 millimole rule” many have heard of. But it’s important to note: 4 mmol/L is only a population-average estimate, and individual variation is actually very large. Some people’s true sustainable ceiling sits at 3 mmol/L, others above 5 mmol/L; blindly applying the number 4 can introduce considerable error.

3. Maximal Lactate Steady State (MLSS)—The “Gold Standard” of Endurance

When talking about lactate, we can’t avoid MLSS (Maximal Lactate Steady State). Its definition is: the highest exercise intensity you can sustain without blood lactate concentration continuously climbing. In rigorous practice, it’s determined as the intensity at which blood lactate rises by no more than about 1 mmol/L during the final 20 minutes of constant-intensity exercise.

MLSS is often regarded as the true physiological ceiling for “how long you can hold on,” and one of the gold standards in the lab. But measuring it is extremely cumbersome—you have to do several 30-minute constant-intensity tests on different days, homing in one session at a time to find the intensity that just barely stabilizes. That’s simply impractical for most people, which is why we need the alternatives below that “estimate it from a single test.”

Historically, it was precisely because Heck et al. tried in the late 1970s to verify whether “MLSS falls exactly at 4 mmol/L” that they found the relationship wasn’t as clean and tidy as imagined—which is why rigorous labs today don’t rely on a single fixed lactate number.

4. Functional Threshold Power (FTP) — The Number Cyclists Know Best

Finally, we get to the FTP (Functional Threshold Power) that Xiao Chen cares about most. FTP is a practical concept developed in the cycling world to bypass the laboratory and allow self-testing with just a power meter. It’s typically defined as “the maximum average power you can sustain for about one hour.” The most popular estimation method is a 20-minute all-out test, with the average power multiplied by approximately 0.95.

FTP’s biggest advantages are that it’s cheap, self-testable, repeatable, and directly corresponds to the power numbers you see in training, which is why it’s the core metric for platforms like TrainerRoad and Zwift. However, it’s a performance/estimation metric, not a direct physiological measurement. What it attempts to approximate is essentially the LT2/MLSS line, but it works backward from “how many watts can you sustain for this hour,” leaving room for variables like pacing ability, willpower, and daily form. The running equivalent is “threshold pace” or Critical Speed, while swimming has CSS (Critical Swim Speed).

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Putting Them All Together: A Comparison Table

This is the table I most often show my athletes to help them untangle the mess of lines in their heads:

Threshold Name	Measurement Method	Invasiveness	Rough Correspondence	Primary Use	Common Error Sources
VT1 (First Ventilatory Threshold)	Respiratory gas analysis	Low (face mask)	Aerobic threshold, upper edge of easy zone	Defining upper limit of low-intensity endurance	Subjective interpretation, equipment accessibility
VT2 (Second Ventilatory Threshold)	Respiratory gas analysis	Low	Anaerobic threshold, sustainable ceiling	Defining starting point of high-intensity training	Subjective interpretation
LT1 (First Lactate Threshold)	Finger/earlobe blood sampling	Moderate (needle prick)	≈ VT1	Mastering the aerobic base zone	Sampling timing, equipment calibration
LT2 (Second Lactate Threshold)	Finger/earlobe blood sampling	Moderate	≈ VT2 / MLSS	Defining threshold training intensity	Inconsistent determination methods
4 mmol/L Fixed Method	Blood sampling	Moderate	Population-average anaerobic threshold	Quick estimation	High individual variability, may be inaccurate
MLSS	Multiple steady-state blood samplings	High (repeated)	Sustainable physiological ceiling	Gold standard validation	Too time-consuming, impractical
FTP	20-min/60-min power test	None	≈ Performance estimate of LT2 / MLSS	Self-prescribed power training zones	Pacing ability, psychology, daily form

When reading this table, I want to emphasize one key point: “Rough correspondence” does not mean “equal.” VT2, LT2, MLSS, and FTP all attempt to describe the same physiological phenomenon—the upper limit of high-intensity effort you can sustain—but they approach it from different angles, and differences of 5% to 10% between the numbers are completely normal. Xiao Chen’s FTP of 240 watts and the lactate report’s 220 watts don’t conflict; they’re just two rulers with slightly different scales, measuring the height of the same wall.

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What Exactly Is the Relationship Between These Thresholds

One Phenomenon, Multiple Projections

I love using an analogy to explain this to athletes: imagine your body’s metabolism as the contour of a mountain, and VT, LT, and FTP are three cameras set up at different angles. The breathing camera (VT) captures the mountain’s respiratory profile, the blood camera (LT) captures its chemical profile, and the power camera (FTP) captures its performance profile. The three photos are of the same mountain, but because the angles differ and the lens errors differ, the photos won’t be identical.

The consensus in the research literature is roughly this: VT1 and LT1 are highly correlated, and VT2 and LT2 are highly correlated, but the agreement between the two methods doesn’t hold in every scenario. The relationship loosens especially during prolonged exercise, with accumulated fatigue, or across different exercise modalities (running vs. cycling). That’s why modern, more rigorous approaches treat them as complementary rather than interchangeable pieces of information.

Why the Discrepancies Occur

Several common reasons explain why the numbers don’t line up:

1. Different testing protocols: How long each stage lasts in a ramp test (3 minutes vs. 1 minute) significantly affects the shape of the lactate curve, which in turn affects where the threshold lands.
2. Inconsistent determination methods: Even just for “lactate threshold,” there are several methods—the D-max method, baseline-plus-fixed-value method, fixed 4 mmol method, etc.—and each gives a different answer.
3. Daily condition: Sleep, the previous day’s training, caffeine, and glycogen stores can all shift the curve.
4. Exercise modality specificity: A threshold measured on the bike can’t be directly transferred to running, because the muscle groups recruited and the economy differ.

This is also why I always tell my athletes: Don’t obsess over the decimal points of a single number. A threshold is a “zone,” not a mathematically precise line.

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Practical Methods: How to Estimate Your Thresholds Without a Lab

Most cyclists and runners in Taiwan won’t have the opportunity to undergo full laboratory gas-exchange plus lactate testing (it’s not cheap, and it’s not available in every city). The good news is that we have several field tests that can approximate quite practically. Here are the methods I actually use with my athletes.

Method 1: The Talk Test — Zero Cost for VT1

This is the cheapest and most underrated tool. The principle is: VT1 falls roughly at the upper edge where you can still speak full sentences comfortably.

• Find a gentle stretch of road or use a trainer, and gradually increase your pace.
• Every one to two minutes, try speaking a passage aloud (e.g., reciting a phone number or a line from a song).
• When you notice that “you need to catch your breath mid-sentence, or your sentences get broken up,” that intensity is approximately around VT1.

Note the heart rate corresponding to that intensity—it’s your upper limit for easy aerobic training. Below it, you’re genuinely building your aerobic base. A common problem among amateur cyclists in Taiwan is “riding too hard on easy days and not pushing hard enough on intervals,” leaving them stuck in the gray zone all day. The talk test can help you hold the lower line.

Method 2: 20-Minute Power/Pace Test — Estimating FTP or Threshold Pace

This is a classic that works for both cycling and running.

Cycling FTP version:

1. Warm up thoroughly for 15–20 minutes, including a few short sprints to open up the body.
2. Ride at the maximum steady effort you can sustain for a full 20 minutes. Pacing is crucial—better to start conservatively and accelerate in the second half than to blow up in the first 5 minutes and collapse later.
3. Take the average power for those 20 minutes and multiply by 0.95—that’s your FTP estimate.

Running threshold pace version: Find a flat stretch of road or a track, run steadily at maximum sustainable effort for 20–30 minutes, and take the pace you can hold steadily in the latter portion—that’s close to your threshold pace. Taiwan’s summers are hot and humid, so I recommend doing this in the early morning or evening, and factoring in the heart rate drift caused by heat (at the same pace, your heart rate will be higher in hot weather—don’t be alarmed).

Method 3: Staged Testing to Estimate Both Thresholds

If you want to capture both the VT1 (aerobic) and VT2 (threshold) lines simultaneously, you can do a step test: start at an easy intensity, increase one level every 3 minutes until exhaustion, record heart rate and power/pace throughout, and mark each stage’s end with “talk difficulty” and “rating of perceived exertion (RPE).” Looking back afterward, you can roughly identify the two turning points: “speech starts to become difficult” (VT1) and “can only utter single words” (VT2).

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Turning Thresholds into Training Zones

Estimating your threshold is just a means to an end—the real goal is using it to decide how hard to push in each workout. Here’s a five-zone system I commonly use (based on FTP or threshold heart rate), mapped to the physiological thresholds discussed earlier:

Zone	Name	% of FTP	Perceived Effort (1–10)	Corresponding Physiological Marker	What This Zone Develops
Z1	Recovery	< 55%	2–3	Well below VT1	Promotes recovery, relaxation
Z2	Aerobic Endurance	56–75%	3–4	Below VT1 / LT1	Builds aerobic base, fat-burning efficiency
Z3	Tempo	76–90%	5–6	Between VT1 and VT2	Improves lactate tolerance, race pace
Z4	Threshold	91–105%	7–8	Near VT2 / LT2 / FTP	Raises sustainable ceiling
Z5	VO2max / Anaerobic	> 106%	9–10	Well above threshold	Lifts VO2max ceiling

The most important lesson from this table: the bulk of your endurance training volume should sit in Z2. This is the essence of “polarized training”—lots of easy work (Z1–Z2) plus a small amount of very hard work (Z4–Z5), while the gray zone of Z3 in between should not dominate. Many amateur riders fail to improve precisely because they ride day after day in Z3—that “somewhat tired but not truly pushing” intensity—accumulating fatigue without delivering a clear training stimulus.

Sample Weekly Schedule (for amateur riders with a base)

Day	Session	Primary Zone	Purpose
Monday	Complete rest or walking	—	Recovery
Tuesday	90 min steady aerobic	Z2	Build base
Wednesday	Threshold intervals 3×10 min @ Z4, 5 min rest between	Z4	Raise FTP
Thursday	60 min easy ride	Z1–Z2	Active recovery
Friday	VO2max intervals 5×4 min @ Z5	Z5	Lift VO2max ceiling
Saturday	Long endurance ride 3–4 hours	Z2 (occasional Z3 climbs)	Endurance and economy
Sunday	Easy ride or social group ride	Z1–Z2	Recovery + fun

Treat this table as an example, not gospel. Adjust the actual scheduling to your recovery capacity, life stress, and race goals. Many amateur riders in Taiwan are busy during the workweek and can only train an hour in the morning and an hour in the evening, saving the long rides for the weekend. In that case, put the long ride on Saturday and schedule threshold intervals on the day you feel best—don’t copy this template rigidly.

Case Study: Xiao Chen’s Three-Month Progression

Back to Xiao Chen. His initial problem wasn’t insufficient fitness—it was that his training distribution was stuck entirely in the Z3 gray zone. Every ride was done at “slightly breathless but manageable,” which looked like hard work, yet his FTP hadn’t budged in six months. After I helped him redistribute his training, we tracked three months of data. The changes are below (all figures are field-test estimates, not precise laboratory numbers, shown only to illustrate the trend):

Metric	Baseline	Week 6	Week 12	Primary Intervention
FTP (watts)	~240	~250	~262	Z2 share increased from 40% to 75%
Talk test VT1 heart rate (bpm)	~148	~152	~156	Large volume of easy aerobic work
Weekly training hours	~6 hours	~7 hours	~8 hours	Less fatigue, able to handle more volume
Subjective recovery (1–10)	4	6	7	Reduced ineffective Z3

The point isn’t those few watts—it’s that he no longer felt tired every day without making progress. As his aerobic base thickened, the same threshold intervals became easier and recovery faster, allowing him to absorb more training volume—a positive feedback loop. This is the most tangible demonstration of “build the foundation thicker first, and the threshold ceiling will grow higher.”

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Supplement: How to Combine Heart Rate, Power, and Perceived Effort

Students often ask: “If I have a power meter, do I still need to watch heart rate?” My answer is that all three play distinct roles, and none can be omitted:

Tool	Response Speed	Strengths	Limitations	Best Use Cases
Power (watts)	Instant	Objective, unaffected by daily fluctuations	Requires a power meter; reflects output, not strain	Defining intensity, interval control
Heart rate (bpm)	Delayed by tens of seconds	Reflects actual bodily strain (heat, fatigue, dehydration)	Drifts; affected by caffeine and emotions	Monitoring fatigue and recovery, long aerobic efforts
Perceived effort (RPE)	Instant	No equipment needed; integrates all internal signals	Requires experience to develop; easily influenced by psychology	Calibrating the other two; braking when something feels off

The most mature approach to training management is: set targets with power, monitor strain with heart rate, and use perceived effort as the final brake. Example: one day you’re scheduled for Z4 intervals, your power hits the target, but your heart rate is abnormally high and the effort feels like a struggle—this usually means you’re not in good shape today (poor sleep, still recovering, or the heat). The smart move is to lower the intensity or call it a day, rather than forcing the power numbers. This is especially true in Taiwan’s summer: heat and humidity push heart rate noticeably higher at the same power output, and in those conditions perceived effort and heart rate will tell you “don’t push it today” earlier than power will.

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Common Mistakes and Fixes

In all my years coaching, roughly 80% of threshold-related mistakes fall into the categories below.

Mistake 1: Treating a Number as an Immutable Truth

Symptoms: Saying “my FTP is 250 watts” for an entire year.

Problem: Thresholds shift with training, season, fatigue, and body weight. If you don’t update for three months, your zones can drift completely off.

Fix: Retest every 6–8 weeks, or at least back-calculate from race/training data. Re-estimate whenever your condition changes significantly (illness, long break, clear improvement).

Mistake 2: Blindly Transferring Numbers Across Sports and Situations

Symptoms: Using your cycling threshold heart rate for running, or applying flat-road numbers to a Wuling climb.

Problem: Different sports, terrain, and temperatures all change the physiological response at the same intensity.

Fix: Build separate zones for each discipline. In Taiwan’s humid summer, accept that “higher heart rate at the same pace” is normal for outdoor training—don’t force winter heart-rate limits onto your summer self.

Mistake 3: Chasing Decimal-Point Precision While Ignoring the Nature of Zones

Symptoms: Losing sleep over whether your FTP is 248 or 251.

Problem: That level of precision is physiologically meaningless; measurement error alone is several percentage points.

Fix: Think of your threshold as a range of roughly ±5%. Training results come from “right direction, consistent over the long term,” not from a decimal point on any given day.

Mistake 4: Training Only the Threshold While Neglecting the Base

Symptoms: Wanting to push Z4 on every ride, feeling Z2 is too slow and “ineffective.”

Problem: Without a solid aerobic base, your threshold ceiling itself can’t grow, and you risk overtraining.

Fix: Honestly hold the upper limit of Z2 (enforced by the talk test), and keep the bulk of your volume in the easy zone.

Mistake 5: Ignoring Warning Signs and Grinding Through the Numbers

Symptoms: You slept poorly, your heart rate is elevated, your legs feel heavy—yet you still follow the plan and force threshold work.

Problem: Threshold training is stressful. Pushing through it while fatigued yields low returns and high risk of injury and overtraining.

Fix: Learn to read morning heart rate, sleep quality, and subjective fatigue. When you’re off, swap Z4 for Z2, or just rest. Training is a long game.

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Actionable Advice for Readers at Different Levels

If You’re a Complete Beginner

Don’t rush to spend money on lab testing, and don’t be intimidated by the alphabet soup of abbreviations. What you should do right now is build your Z2 feel using the talk test, putting about 80% of your training volume at an easy intensity where you can still “speak in full sentences,” gradually building a thicker aerobic base. This stage offers the most room for improvement and requires the least precise numbers.

If You’re an Intermediate with One to Two Years of Experience

You can start using a 20-minute test to estimate FTP or threshold pace, establish a five-zone system, and try polarized training—plenty of Z2 plus 1–2 solid Z4/Z5 interval sessions per week. Remember to retest and recalibrate every 6–8 weeks. This is when threshold numbers truly begin to provide meaningful guidance for your training.

If You’re a Competitive Athlete Seriously Preparing for Races

If your goal is a hard event like the Westbound Wuling or KOM, and your budget allows, consider getting a full gas exchange plus lactate test at a facility that performs sports physiology testing. Capturing both VT1/VT2 and the lactate curve in one session will define your multiple training zones more precisely than a pure field test. But treat it as “a deep check-up to calibrate your existing field tests,” not as a replacement for day-to-day training management using power or heart rate.

A Reminder for Everyone: Make Sure It’s Safe to Exercise First

Threshold training, especially Z4/Z5, pushes the cardiovascular system to quite high intensities. If you are older, have a family history of heart disease, high blood pressure, diabetes, or have been sedentary and are just starting to exercise, please consult a physician and get an appropriate cardiopulmonary evaluation before starting a high-intensity training plan. Taiwan’s National Health Insurance makes it easy to see a doctor; a family medicine or cardiology clinic can help with basic screening. Don’t skip this step. You exercise to make your body better, not to take unnecessary risks.

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FAQ

Q: Is the “threshold heart rate” auto-estimated by my watch accurate?
A: It’s acceptable as a starting reference, but it’s derived from an algorithm and may not match your true physiological threshold. We recommend calibrating it with a field test rather than trusting it completely.

Q: Is lactate really what causes heavy legs?
A: No. Delayed onset muscle soreness (DOMS) is mainly related to micro-damage in the muscle and the inflammatory repair process, and has little to do with lactate. Lactate is metabolized quickly after exercise ends.

Q: Should I track VT, LT, or FTP?
A: For the vast majority of amateurs, using FTP/threshold pace combined with heart rate and RPE to manage training offers the best value. VT/LT testing is suitable for those who want more precision or need a deep recalibration when hitting a plateau.

Q: How often should I retest?
A: Generally every 6–8 weeks; retest sooner if you’ve just finished a training block, are returning after illness, or have had a significant change in body weight.

Q: Is it normal for my numbers to get worse during Taiwan’s summer training?
A: Very normal. Heat and humidity significantly increase cardiovascular strain; at the same power output, heart rate runs higher and perceived effort feels harder. In summer, focus primarily on power/pace, use heart rate as a secondary reference, and pay special attention to hydration and electrolyte intake.

Q: How should I fuel during threshold training?
A: High-intensity training above threshold relies heavily on carbohydrates (glycogen). If you have a longer or more intense threshold session that day, make sure glycogen stores are full beforehand and take in carbohydrates during the session—this helps you sustain intensity and supports recovery afterward. For longer sessions (over roughly 90 minutes), fueling on the go is especially important. With Taiwan’s convenient food options, a normal balanced diet is usually enough to support amateur training volume; you don’t need to lean on expensive supplements. If you have special nutritional needs or chronic conditions, consult a dietitian for an individualized fueling plan.

Q: Can I train threshold with only a heart rate monitor and no power meter?
A: Absolutely. Use the talk test and a 20–30 minute all-out test to find your threshold heart rate, and you can build heart-rate-based zones. Just remember that heart rate has a lag and drift, so combining it with perceived effort during short intervals will make it more accurate.

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Conclusion: Don’t Let Abbreviations Hijack Your Training

Back to Xiao Chen’s three numbers from the opening. What I told him in the end was: “None of those three numbers is lying to you—they’re just looking at the same thing from three different windows: breathing, blood, and power—your sustainable high-intensity ceiling. They won’t be exactly equal, and that’s normal. What you need to do isn’t obsess over which one is ‘real,’ but pick one you can measure consistently and that directly guides your training (for you, that’s FTP), use it well, and recalibrate every two months.”

The science of thresholds is fascinating, but its practical value isn’t in memorizing every abbreviation—it’s in helping you answer a very simple question: How hard should I push, and how fast should I go, in this session? As long as you can answer that question consistently and honestly respect your body’s state and recovery, you’re already on a smarter path than most people who are stuck in the gray zone, training aimlessly.

Treat numbers as servants, not masters. May you ride long, run far, and enjoy the process.

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This article is educational content and does not replace individual diagnosis or treatment advice from a physician, physical therapist, or dietitian. If you have cardiovascular disease, high blood pressure, diabetes, or other chronic conditions, or belong to a higher-risk group for exercise, please consult a qualified medical professional and undergo individualized assessment before starting high-intensity training.

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References

• The Relationship Between Lactate and Ventilatory Thresholds in Runners (Frontiers in Physiology / PMC): https://pmc.ncbi.nlm.nih.gov/articles/PMC6167480/
• The origin of the maximal lactate steady state (MLSS) (BMC Sports Science, Medicine and Rehabilitation / PMC): https://pmc.ncbi.nlm.nih.gov/articles/PMC10840223/
• Ventilatory Threshold - an overview (ScienceDirect Topics): https://www.sciencedirect.com/topics/nursing-and-health-professions/ventilatory-threshold

Related Reading

• Ventilatory Threshold vs. Lactate Threshold: Similar but Distinct Physiological Boundaries
• Lactate Threshold Fully Explained: LT1, LT2, and the Anchors of Training Zones
• Lactate Threshold Training: How to Find Your Critical Cycling Pace
• Lactate Threshold vs. FTP: A Complete Breakdown of the Two Most Confused Training Metrics