Polarized Training vs. Threshold Training: What the Scientific Literature Says and How Age-Group Athletes Should Train

Coach’s Opening: That Athlete Who “Works Hard Every Day, Yet Is Stuck at the Same Results Forever”

Let me start with a real scenario I’ve coached (I’ve changed the personal details, but the training pattern is exactly the same).

A-Jhe, 38, a tech-industry engineer and father of two, can squeeze out about 8 to 10 hours of training time per week. When he came to me, his split times for a 113 half-ironman were all pretty “mediocre”—a 40-minute swim, an average bike power of around 195 watts, and a run pace stuck at about 5:20 per kilometer. No matter how he trained, he couldn’t break through.

I looked at his training logs from the previous three months, and my first reaction was: “You’re riding every single session way too hard.” He proudly said, yeah, I give it my all every time. That was exactly the problem. His power distribution was almost entirely concentrated in an awkward middle ground—not easy enough to build a large aerobic base, and not hard enough to truly force high-intensity adaptations. In exercise science, this has a name: the “grey zone,” and it’s the most common trap I’ve seen age-groupers fall into over the past 15 years.

A-Jhe’s problem wasn’t a lack of effort—it was a wrong training intensity distribution (TID). And the “polarized training vs. threshold training” debate is precisely about this: given your weekly training time, how should you allocate it across different intensities? In this article, I’ll lay out the research literature clearly, and then give you—whether you’re a first-time finisher or a veteran chasing a podium spot in your age group—a practical, executable plan.

I want to start with a statement that might offend some people: Whether you train hard, I can tell from your stagnant results; but whether you train smart, only your intensity distribution reveals that. Over these 15 years, most of the “speed gains” I’ve helped athletes achieve didn’t come from telling them to train more or train harder, but from reallocating the time they were already spending. Time is limited—how you slice it determines your ceiling. That’s why this topic of intensity distribution is worth ten minutes of your careful reading.

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Conceptual Foundation: Three Zones, Five Zones, and Where That “Threshold” Actually Is

To discuss polarization and threshold, we first need to clarify the intensity coordinate system, or everything after this will be talking past each other.

The most common framework in exercise physiology is the three-zone model, which uses two “ventilatory thresholds” or “lactate turning points” to divide intensity into three blocks:

• Zone 1 (low intensity, LIT): Below the first lactate threshold. Perceptually, it’s “can still chat easily”—you can speak full sentences without gasping. Blood lactate is roughly below 2 mmol/L.
• Zone 2 (threshold/moderate intensity): Between the first and second lactate thresholds. This is the “a bit breathless, speech gets shorter, but still manageable” zone. Blood lactate is roughly 2 to 4 mmol/L. This zone is the so-called grey zone.
• Zone 3 (high intensity, HIT): Above the second lactate threshold. VO2max intensity, interval efforts—you can only squeeze out a few words at a time.

Note that this “Zone 2” is not the same thing as the “Zone 2” in the five-zone heart-rate model many people have on their watches—this is the most common point of confusion for beginners. Zone 2 in the three-zone model actually corresponds to Z3–Z4 in the five-zone model (sweet spot, threshold), not that easy aerobic slow-ride Z2. When you see the words “Zone 2,” first confirm which model the person is referring to—I’ll emphasize this again later.

Two Main Allocation Philosophies

Spreading your weekly training volume across these three zones gives rise to several mainstream distributions:

Model	Zone 1 (Low)	Zone 2 (Threshold)	Zone 3 (High)	One-Line Characteristic
Polarized	75–80%	~5%	15–20%	Heavy at both ends, empty in the middle
Threshold	Less	Heavily concentrated here	Little	Focus on sweet spot/threshold
Pyramidal	Most	Moderate	Least	Decreasing from low to high
HIIT-Dominant	Little	Little	A lot	All intervals

The spirit of polarized training is “either very easy, or very hard—don’t stay in the middle.” Roughly 80% of training time goes into genuinely easy Zone 1, 20% into genuinely hard Zone 3, and the middle threshold zone is deliberately left empty. This is the famous “80/20 rule.”

Threshold training, by contrast, invests a large amount of time near the lactate threshold (i.e., the grey zone), with the rationale: “This is the intensity where racing happens, so I should train at this intensity a lot.” It sounds intuitive, which is exactly why so many self-taught age-groupers unconsciously become threshold-dominant—including A-Jhe from the opening.

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What the Science Says: Where the 80/20 Number Comes From

Let me first debunk a misconception: 80/20 was not “designed” as an optimal solution in someone’s lab—it was “observed.”

The Origin: First, Observe What Elite Athletes Do

This model is primarily associated with the research of exercise physiologist Stephen Seiler. What he did was quite straightforward—he tracked how world-class athletes in endurance sports like cross-country skiing, rowing, cycling, and running actually trained, logging every session and categorizing it by zone. The result was a pattern consistent across sports: these elite athletes spent roughly 80% of their training time at low intensity, 20% at high intensity, and used the middle threshold zone very sparingly (Background on Seiler’s research, Roadman Cycling).

In other words, Seiler didn’t invent 80/20—he discovered that elite athletes were independently training this way. This order matters: the phenomenon came first, then the theory.

Is There a Controlled Experiment Proving It’s Better?

Just saying “elite athletes all train this way” isn’t fully convincing—maybe they’re strong despite training this way, not because of it. So we need randomized controlled trials (RCTs).

One frequently cited study compared several different intensity distribution blocks, and the results showed that the group using a polarized distribution saw the greatest improvement in VO2peak (peak oxygen uptake), increasing by approximately +6.8 ml·min·kg⁻¹, or about 11.7%, significantly outperforming the threshold training group (Stöggl & Sperlich 2014, Frontiers in Physiology). This is the trump card most often played by the polarized training camp.

Subsequent systematic reviews support a similar direction: after synthesizing multiple studies, one systematic review noted that combining 15–20% high-intensity with 75–80% low-intensity is most favorable for short-term improvements in VO2max, VO2peak, and work economy (Systematic Review, MDPI Sports 2024).

But—Don’t Throw Out Threshold Training Just Yet

This is the part I most want to share, and it’s also what many internet cheat sheets won’t tell you: larger-scale analyses in recent years have made this conclusion far less one-sided.

A systematic review and multi-level meta-analysis targeting “trained cyclists” found that once enough studies were included (38 studies for the VO2max portion), polarized and non-polarized training approaches produced fairly comparable improvements in VO2max and time-trial performance (Systematic Review & Meta-analysis, ScienceDirect / JSAMS 2024).

The earlier meta-analyses that declared “polarized wins outright” had very small sample sizes (some included only 4 studies) and high heterogeneity, so their conclusions were easily swayed by a few studies with strong effects. Once the research base expanded, the gap narrowed.

So the honest conclusion is:

1. Polarized training being “effective” is certain—it reliably improves VO2max and exercise economy.
2. Polarized being “clearly superior to threshold”—this doesn’t hold up well in the newest, larger-scale evidence. The two are more like “both work, with little difference between them.”
3. What actually gets repeatedly debunked is the all-week gray-zone, naturally evolved distribution that’s neither easy enough nor hard enough.

This is actually good news for age-group athletes: you don’t need to lose sleep agonizing over “choosing the right school.” The number-one enemy you need to avoid is the gray zone—not “choosing polarized vs. threshold.”

Why “Lots of Easy” Makes Physiological Sense

Many people intuitively struggle to accept “to get faster, train slower more,” finding it counterintuitive. But from a physiological mechanism standpoint, large volumes of low-intensity training do several things that high-intensity sessions cannot:

• Mitochondrial and capillary proliferation: Prolonged low-intensity aerobic stimulation is the primary driver of mitochondrial density and capillary network expansion in slow-twitch muscle fibers. This is the displacement of your “aerobic engine,” determining how cheaply you can sustain a given pace.
• Fat metabolism efficiency: Low-intensity zones make your body better at using fat as fuel, saving precious glycogen for the later stages. For multi-hour events like 113 and 226, this is almost the deciding factor.
• Low recovery cost: Low-intensity sessions place far less stress on the nervous, muscular, and endocrine systems than intervals. They let you accumulate “volume” both heavily and safely, and volume is the most foundational layer of endurance performance.

The high-intensity 20% does something else: it directly raises the VO2max ceiling, boosting maximal cardiac output and lactate tolerance. The division of labor is clear—easy work builds engine displacement; hard work builds the engine’s redline. The gray zone in between is awkward precisely because it does only half of each job, yet carries a recovery cost that isn’t low—the worst cost-performance ratio.

This is also why “train slow more” isn’t about being laid-back; it’s a mechanism-backed strategy: you enlarge the foundation at low cost, then use a small amount of expensive sessions to push the ceiling.

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The Pyramidal Distribution: The Overlooked Third Option That May Suit Age-Group Athletes Best

The media loves to package this as a “polarized vs. threshold” two-way showdown, but in the real world there’s a third option—and personally, when coaching busy age-group athletes, I use it more than pure polarization—that’s the pyramidal distribution.

Pyramidal means: the most low intensity, moderate threshold, the least high intensity, with volume tapering off layer by layer from the bottom up, like a pyramid.

Its biggest difference from polarized lies in whether the middle threshold layer is left blank:

• Polarized: lots of low, almost no threshold, a decent amount of high.
• Pyramidal: lots of low, some threshold, the least high.

Why Is Pyramidal Often a Better Fit for Age-Group Athletes?

There are several very practical reasons:

1. Long-distance events like 113/226 have race intensities that naturally fall below threshold. Your bike leg is roughly at 70–80% of FTP (for 113) or lower (for 226), which is already near the sweet spot/sub-threshold. A moderate amount of threshold work has “specificity.”
2. Pure polarized high-intensity sessions are punishing. Swallowing a full weekly dose of true Zone 3 intervals, when you’re sleep-deprived and stressed from work, often means recovery can’t keep up—resulting in chronic fatigue or even injury.
3. In many studies, elite athletes also “drift” from polarized to pyramidal as the season approaches, because they need to add more race-specific intensity.

So my practical recommendation is usually: lean polarized in the base period (lots of easy + a little high intensity to sharpen VO2max), then shift toward pyramidal near race season (keep the easy base, add more race-pace/sub-threshold specific sessions). This isn’t compromise—this is periodization.

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Practical Approach: How an 8-Hour-Per-Week Age-Group Athlete Should Split Intensity

Enough theory—here’s something you can copy directly. Let’s use A-Zhe, an age-group triathlete training “8–10 hours a week across all three disciplines,” as the template.

First, Get This Straight: Does 80/20 Count “Time” or “Reps”

This is another super common mistake. 80/20 refers to “proportion of time,” not “proportion of workout reps.”

Say you train 8 hours a week = 480 minutes. 80/20 means:

• Low intensity Zone 1: about 384 minutes (6.4 hours)
• High intensity Zone 3: about 96 minutes (1.6 hours)

Note that in a 60-minute interval session, the actual time spent in Zone 3 might only be 20–25 minutes; the rest is warm-up, recovery between reps, and cool-down. So scheduling 2–3 interval sessions a week usually already approaches or even exceeds that 20% high-intensity time budget. All remaining time—keep it easy.

The most common mistake beginners make is riding their “easy days” into the slightly breathless gray zone, turning the actual distribution into 50/40/10, with neither end done properly.

Sample Weekly Schedule (Age-Group Triathlete, Base Period Leaning Polarized)

Day	Discipline	Intensity	Key Content
Mon	Rest / Stretching	—	Complete rest or light yoga, no sessions scheduled
Tue	Run	High Z3	After warm-up, 6×3 minutes in VO2max zone, 2-minute easy jog between reps
Wed	Swim + Bike	Low Z1	Swim technique session + easy evening ride 60–75 minutes, conversational pace
Thu	Bike	High Z3	After warm-up, 5×4 minutes near/above FTP, 3 minutes between reps
Fri	Run	Low Z1	Easy aerobic 40–50 minutes, pace deliberately set to “almost embarrassingly slow”
Sat	Bike LSD	Low Z1	Long endurance ride 2.5–3 hours, all Zone 1, practice fueling
Sun	Run (can follow bike)	Low Z1	90-minute easy long run or brick, watch that HR doesn’t drift

The soul of this table: only Tuesday and Thursday are true hard sessions; everything else is easy. Two high-intensity sessions plus roughly 6 hours of easy volume per week makes for a very clean polarized week.

How to Structure High-Intensity Workouts: It’s Not About Hurting More

Many people think a high-intensity workout means “pushing until you puke,” but intervals of different durations actually stimulate different systems. Here’s a comparison chart of interval workouts I commonly use, so you can make that 20% of time purposeful:

Workout Type	Typical Structure	Primary Stimulus	Best Placed In
Short Intervals	30 sec × multiple sets, 1:1 recovery	Neuromuscular, anaerobic power	Pre-season seasoning
VO2max Intervals	3–5 min × 4–6 sets	VO2max ceiling	Base period staple
Threshold/Sub-Threshold	8–20 min × 2–3 sets	Lactate threshold, race tolerance	Pre-race specific phase
Race Pace	20–40 min continuous	Specific rhythm, fueling rehearsal	6–10 weeks pre-race

Key reminder: In the base period, focus on VO2max intervals; only shift the emphasis to threshold and race pace before racing. This is exactly what “polarization drifting into a pyramid” looks like on a training plan. Don’t run the same intervals year-round.

Back to A-Zhe: What I Actually Changed in Three Months

To be specific, A-Zhe’s adjustments were only three things, nothing fancy:

1. Split up the two weekly “hard rides”: One became a true VO2max interval session (hurting properly and completely), the other was cut down to easy aerobic riding.
2. Capped the power ceiling on weekend long rides: I required him to never exceed a certain power for the entire ride; if he did, he had to automatically shift down, forcing him to stay in Zone 1. He struggled at first, thinking “am I even training?”, but after two months he started enjoying that feeling of still having plenty of energy after the ride.
3. Added long race-pace segments for a 113 8 weeks before the race: Gradually drifting from polarized training in the base period to a pyramid with specific work included.

No magic, no wonder tools—it’s just reallocating time.

Execution Details for Taiwan

Here are a few reminders I think are particularly relevant for Taiwanese athletes:

• Easy long ride routes: In the north, routes like Beiyi or Fengguizui are actually unfriendly to “easy Zone 1” because the climbs force you into threshold. For pure Zone 1 long mileage, riverside paths (Dahan River, Xindian River, Tamsui River bike paths) or the relatively flatter sections of Provincial Highway 11 and 9 in the east are easier to control intensity. Treat climbing days as high-intensity days; don’t pretend they’re easy rides.
• Climate and heart rate drift: Taiwan’s summers are hot and humid. At the same power, heart rate will drift upward (cardiovascular drift). So for low-intensity sessions in summer, use power or perceived exertion (RPE) as the primary control, not heart rate. Otherwise, you’ll either ride slower than necessary to keep HR down, or misjudge the heat as overtraining.
• Eating out for fueling: Age-group athletes often schedule long rides on weekend mornings. Taiwan’s breakfast shops are super convenient, but don’t down a greasy egg pancake with milk tea before a long ride. 2–3 hours before, focus on easily digestible carbs (rice balls, toast, onigiri, sweet potatoes are all good). During the ride, take in 30–60 grams of carbs per hour.

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Common Mistakes and Fixes: The Five Pitfalls I Most Often Catch for My Athletes

Mistake 1: Easy Days Too Fast (The Gray Zone Trap)

This is the number one problem, and A-Zhe was a classic case. Fix: On low-intensity days, deliberately go slow enough to feel “a bit boring, even like you’re slacking off.” A useful check: can you recite a full sentence smoothly without gasping the entire ride? If not, you’re going too fast.

Mistake 2: High-Intensity Days Not Hard Enough

Some people overcorrect. They hear “go easy,” so they even slack off on interval days, making the whole week lukewarm—neither end done properly. Fix: High intensity must be genuinely high. In the VO2max zone, you should be breathing hard; you should want to lie down afterward. The premise of polarization is that “high intensity is truly high enough,” otherwise it degrades into ineffective low-intensity-dominant training.

Mistake 3: Treating “80/20” as the Ratio Within Every Single Session

Fix: 80/20 is the distribution of total weekly time, not a mandate that every session be 80% slow and 20% fast. Easy sessions are easy all the way through; interval sessions are for doing intervals properly. Don’t turn every session into a mishmash.

Mistake 4: Confusing Zone 2 on a 5-Zone Watch with Zone 2 in a 3-Zone Model

Fix: As mentioned earlier, these two “Zone 2s” are worlds apart. When discussing polarization, “easy base” corresponds to low intensity where you can chat easily (often shown as the lower end of Z1–Z2 on a 5-zone watch). When you see someone mention Zone 2, first confirm which model they’re using.

Mistake 5: Using the Same Distribution Year-Round

Fix: Periodize. In the base period, lean polarized to build the aerobic engine and VO2max; closer to racing, drift into a pyramid and add race-specific pace. The distribution evolves with the season—it’s not about picking one school and sticking with it forever.

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Actionable Advice for Athletes at Different Levels

First-Timer Finisher Group (Goal: Finish Healthy)

Honestly, at this stage, “total volume” and “consistency” matter far more than “the details of intensity distribution.” Your first priority is to build a sustainable, injury-free routine you can maintain.

• Put 80%+ of your time into easy aerobic work to build a foundation for running, riding, and swimming.
• Just 1 high-intensity session per week, or even none for the first few months—add it once your body has adapted structurally.
• Don’t obsess over polarization vs. pyramid. What you need most right now is “more easy, fewer injuries, build the habit.”

Advanced Age-Group Athlete (Goal: Age-Group Results, PB)

This is the group that benefits most from intensity distribution, because you’re the most prone to falling into the gray zone.

• Review your files from the past 4–6 weeks and calculate your true three-zone time distribution. If your middle threshold zone exceeds 30%, you’re likely a gray-zone type—time to polarize it away.
• Run clean 80/20 in the base period: 2 high-intensity sessions per week, everything else easy.
• In the 8–10 weeks before racing, gradually drift into a pyramid, swapping some high-intensity work for race-pace/sub-threshold specific sessions (e.g., for a 113, do more long segments near race power).

Veteran Gunning for an Age-Group Podium / Long-Distance Qualification

Your training volume is high, and your recovery capacity has been built up, so you can handle more structured planning.

• The higher your training volume, the more you must protect that large low-intensity base; otherwise, accumulated fatigue from high-intensity work will crush you. High-volume athletes actually need polarization more to survive.
• Manage the quality of high-intensity sessions more precisely: VO2max sessions, threshold sessions, and race-pace sessions each have their purpose—don’t blend them all together.
• Use HRV, morning pulse, sleep, and subjective fatigue as your dashboard. When recovery indicators flash red, cut high-intensity work first and preserve easy volume, rather than forcing the plan through.
• Taiwan’s long-distance target races (e.g., domestic or international 226s or big 113s) often fall in hot, humid seasons. Build heat adaptation and fueling rehearsal into your periodization—don’t wait until the week before. Long rides are the best fueling testing ground.

A Simple Self-Check for Everyone

No matter your level, do this when you get home: open your training files from the last 4 weeks, classify each session into low/threshold/high zones, and roughly calculate the time percentage.

• If your middle threshold zone exceeds 30%: congratulations, you’ve found the culprit—you’re the gray-zone type. Start by making your easy sessions easy.
• If low intensity is below 70%: your foundation is being built too hastily, risking hitting a wall or injury. Shift volume toward the easy end.
• If high intensity has been 0% for a long time: you might be training safely but lacking ceiling stimulus, so performance will plateau. Time to add some structured intervals.

This five-minute self-check is far more useful than agonizing over “which school to pick.”

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FAQ

In actually coaching athletes, these questions come up from almost everyone—let me answer them all at once.

Q1: I don’t have a power meter or a lactate meter. How do I know which zone I’m in?

The talk test is more than enough—it’s the oldest and most reliable zone tool:

What you can do	Approximate zone
Recite full sentences smoothly and keep chatting	Zone 1 low intensity
Can only manage short phrases, need to catch your breath to continue	Zone 2 threshold (gray zone)
Can only squeeze out a few words, barely able to speak	Zone 3 high intensity

Pair this with rating of perceived exertion (RPE 1–10): Zone 1 is roughly 3–4, Zone 3 is roughly 8–9. You don’t need to spend big money to train right.

Q2: I only have 5 hours a week. Does 80/20 still apply?

It applies, but you need to be more pragmatic. The less time you have, the more important it is to “not waste time in the gray zone,” because you simply can’t afford ineffective training. With 5 hours, I usually schedule 1 solid high-intensity session + everything else easy, keeping the ratio roughly around 80/20, just with fewer high-intensity sessions.

Q3: Won’t polarized training make me less accustomed to race intensity?

This is exactly why periodization matters. The base phase can be highly polarized, but 6–10 weeks before race day you must add race-pace specific sessions so your body gets used to the intensity and rhythm you’ll actually face. Training purely polarized all the way to race day without specific work does carry this risk—which is why I emphasize drifting toward a pyramid in the later phase.

Q4: For run, bike, and swim, should the 80/20 be calculated separately or combined?

In practice, look at overall training load—combine all three and aim for the big picture; you don’t need to nail 80/20 for each discipline. But note that injury risk differs by discipline: running has the highest impact, so high-intensity run sessions should be the most conservative; swimming and cycling have lower impact and tolerate high intensity better. For running, it’s better to do fewer high-intensity sessions than to risk injury.

Q5: So should I choose polarized or pyramid training?

If you really want a lazy answer: polarized in the base phase, pyramid in race season, and avoid the gray zone year-round. For the vast majority of age-group athletes, this combination has the highest margin for error and is least likely to cause injury or overtraining. Rather than splitting hairs over which camp you belong to, put your energy into two things: “Are my easy sessions truly easy, and are my hard sessions truly hard?”

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Conclusion: Stop asking “which camp is stronger,” first ask “am I falling into the gray zone”

Back to A-Zhe. The first thing I did for him wasn’t converting him into a polarized-training disciple—it was a boring request: on easy days, actually ride slow. Just by splitting those “in-between effort rides” into “truly easy long rides” plus “truly painful intervals,” his cycling threshold power moved up a notch after three months, and his running started to loosen up too—he didn’t train harder, his effort distribution was right.

After reading all this literature, here are the three core takeaways I want you to leave with:

1. 80/20 polarized training is a pattern observed in elite athletes and has been shown to effectively improve VO2max and economy.
2. The claim that polarized “clearly beats” threshold training isn’t so absolute in the latest, larger-scale evidence—both are effective, and the difference is limited.
3. The real common enemy is the gray zone. Whether you believe in polarized or pyramid, if you keep easy sessions easy, hard sessions hard, and avoid that middle sludge, you’re already ahead of most age-group athletes.

Intensity distribution isn’t a religion—it’s a tool. Pick a version that fits your lifestyle and that you can recover from, then execute it consistently for several months—that will make you faster than arguing about which camp is best online.

This article is educational content and cannot replace individual assessment by a physician, physical therapist, or nutritionist. Please adjust training intensity and fueling plans based on your personal health status, existing injuries, and professional evaluation.

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References

• Stöggl & Sperlich, Polarized training has greater impact on key endurance variables than threshold, high intensity, or high volume training — Frontiers in Physiology (2014): https://www.frontiersin.org/journals/physiology/articles/10.3389/fphys.2014.00033/full
• The Effect of Polarized Training Intensity Distribution on Maximal Oxygen Uptake and Work Economy Among Endurance Athletes: A Systematic Review — MDPI Sports (2024): https://www.mdpi.com/2075-4663/12/12/326
• The effect of training distribution, duration, and volume on VO2max and performance in trained cyclists: A systematic review, multilevel meta-analysis — ScienceDirect / JSAMS (2024): https://www.sciencedirect.com/science/article/pii/S1440244024005966
• Stephen Seiler 80/20 Polarised Training background summary — Roadman Cycling: https://roadmancycling.com/blog/stephen-seiler-80-20-polarised-training-cyclists

Related Reading

• Polarized vs. Pyramid Training: Physiological Evidence and Application Scenarios for Two Intensity Distributions
• Intensity Distribution in Triathlon: Polarized vs. Threshold Training Applied to Triathlon
• Polarized vs. Threshold Training: Why 80/20 Keeps Winning Among Elites
• Polarized vs. Threshold vs. Pyramid Training: How to Choose Among Three Intensity Distribution Philosophies?