You Don’t Have to Train by Power. But Your Zones Should Come From CP, Not FTP.

Pace, heart rate, lactate, RPE — every one of them works, and we coach all of them. What decides whether they’re accurate isn’t which metric you pick. It’s what sits underneath. Here’s the research.

Two things are true at once, and the endurance world keeps insisting you pick one.

First: power is the gold standard. A power meter measures your output directly. It doesn’t lag, it doesn’t drift in the heat, it isn’t distorted by hills or wind or how you slept. If you can train with power, do — we recommend it.

Second: you absolutely do not have to. Pace, heart rate, lactate, and rate of perceived exertion are all legitimate ways to train, and we coach every one of them. Plenty of our athletes race extremely well without ever looking at a watt.

Here’s what actually decides whether your training is accurate — and it’s the question almost nobody asks: what are your zones anchored to? Because a gold-standard instrument pointed at a flawed reference still sends you to the wrong place. Which is exactly what happens in most training plans, whichever metric they use.

The Problem: Four Rulebooks That Don’t Agree

Look at how conventional plans assign intensity. Each metric gets its own borrowed system, and none of them were derived from the same physiological event:

So when your Zone 3 by power says one thing and your Zone 3 by heart rate says another, your body isn’t contradicting itself. The math is.

CP vs. FTP: why the anchor matters most

Start with the one nearly everyone uses. FTP is a convention. CP is a parameter. That’s not semantics — it’s the whole difference. FTP comes from a 20-minute test with a population-average correction (usually 95%) applied to every athlete regardless of who they are. Critical Power falls out of the actual mathematical relationship between the intensity you can produce and how long you can hold it, measured across multiple efforts. One is an estimate borrowed from a group average. The other is a property of your own physiology.

The research bears this out. A systematic review found FTP is reasonably reliable but has limited physiological validity against classical lactate and ventilatory thresholds — and subsequent work concludes FTP is not a physiologically valid marker of the maximal metabolic steady state. When CP and FTP were measured head-to-head in the same cyclists, there was a 91.7% probability that CP was higher than FTP, averaging about 7 watts apart — a gap larger than the smallest meaningful change in power for an endurance athlete.

They are not interchangeable. And here’s the part that reaches every athlete, not just the ones with power meters: if your anchor is off, every metric derived from it is off too. Your heart rate zones, your pace targets, your effort cues — all of them inherit the error. The anchor is upstream of everything.

And max-HR percentages are worse

This is where conventional zones fall apart completely. Research on individual variation shows heart rate at the first threshold varies between athletes with a coefficient of variation of 20–29%. LT1 can occur anywhere from 45% to 70% of max heart rate. LT2 ranges from around 55% of max in untrained individuals to 93% in elite athletes. On top of that, a 40-year-old’s true max HR might be anywhere from 160 to 200 — so an age-based formula can be off by 8–10 beats at every single zone boundary.

The Fix: One Model, Anchored to Real Breakpoints

Every ANC zone is anchored to two measured physiological turn points — LT1 (where lactate first rises above baseline) and LT2 (the maximal metabolic steady state, the boundary between sustainable and unsustainable). We locate those using Critical Power (CP) on the bike and Critical Speed (CS) — pace — on the run.

The distinction matters: FTP is a convention. CP is a parameter — it falls out of the actual mathematical relationship between the intensity you can produce and how long you can hold it. On the run side, research shows VO₂ stays stable just below Critical Speed but climbs to VO₂max just above it, confirming CS marks the true sustainable boundary — and that conventional MLSS lab testing actually underestimates the real maximal metabolic steady state.

Once we know where your LT1 and LT2 actually sit, every other metric becomes a translation of the same two breakpoints — not a separate system. Here’s what that looks like.

Bike Training Zones

LT1 sits at 79% of CP. LT2 sits at 100% of CP. Every row below is the same physiology, read a different way.

Run Training Zones

LT1 sits at 85% of CS. LT2 sits at 105% of CS. Note that run power gets its own row — if you use a running power meter, it’s anchored to the same model.

Why These Charts Are More Accurate Than What You’ve Been Given

Three structural differences, and they compound:

And because every row derives from the same two breakpoints, the metrics agree with each other. Your Z2 by power, your Z2 by heart rate, and your Z2 by feel all describe the same physiological state. That’s not true in a system stitched together from four different sources.

Which unlocks the part serious athletes care about most: once your metrics are aligned, the gaps between them become real information. Heart rate climbing while power stays flat late in a long ride is a genuine durability signal — not noise from mismatched systems.

No Power Meter? Here’s Exactly How We Coach You

This is the part most coaching skips. “Train by heart rate” is useless advice without saying which heart rate, anchored to what. Here’s the actual method for each.

Heart rate — anchored to your threshold, never your max

We find your threshold heart rate — the HR you hold at LT2 — from a field test, then express every zone as a percentage of that, not of an estimated maximum. This is the single most important correction available to a non-power athlete, and the research is emphatic: HR at the first threshold varies between individuals with a coefficient of variation of 20–29%. LT1 can occur anywhere between 45% and 70% of max HR; LT2 ranges from roughly 55% of max in untrained athletes to 93% in elites. Two athletes riding at “75% of max” can be in genuinely different physiological states. Anchoring to threshold HR eliminates that error entirely.

We also coach you to expect drift. Heart rate lags 30–120 seconds behind a change in effort and climbs over a long session as you heat up and fatigue — that’s normal physiology, not lost fitness. So we prescribe HR for steady aerobic work where it’s reliable, and lean on pace or RPE for short intervals where the lag makes it useless.

Pace — Critical Speed is a genuine gold standard of its own

Runners should know this: on the run, you’re not settling for second best. Critical Speed is measured the same way as Critical Power — from the relationship between how fast you can go and how long you can hold it — and research shows VO₂ stays stable just below CS but climbs to VO₂max just above it. That’s direct evidence CS marks the true sustainable boundary. In fact, the work suggests conventional lab MLSS testing underestimates the real maximal metabolic steady state. A GPS watch and a proper CS test give you a physiologically valid anchor.

Pace’s weakness is terrain, wind, and heat — the same effort is legitimately slower uphill. So we prescribe pace on controlled terrain and switch you to RPE or HR on hills, trails, and hot days rather than pretending the number still applies.

RPE — calibrated against your own threshold, not a generic chart

Most plans hand you a 1–10 scale copied from a textbook. We do the opposite: during your testing we record what your zones actually feel like to you — your breathing pattern, your talk test, your effort sense at LT1 and LT2 — and build your personal RPE anchors from that. Your 5 is your 5, measured, not assumed.

RPE is a well-validated measure of exercise intensity, and it has one advantage no device has: it integrates everything at once — fatigue, heat, fuel, sleep, stress. It’s the only metric that already accounts for the fact that today isn’t yesterday. That’s why we use it as the cross-check on every session, even for athletes with a full sensor setup.

Now Running at 100% in Comprehensive Coaching

This is the update we’re most excited about. ECHO Comprehensive athletes now get the complete metric suite — power, pace, heart rate, RPE, and lactate targets — all derived from their own tested CP and CS, across bike and run. Not a power plan with heart rate bolted on. One physiological model, fully expressed in every metric you can measure.

Get the power meter — it’s the gold standard and it will make you a sharper athlete. But whether you show up with a full setup or a watch and your own breathing, the zones you train in trace back to the same physiology. That’s the standard we hold everything to.

Go deeper: What is Critical Power & Critical Speed? →  ·  Your Zones Cheat Sheet →  ·  Physiological Profiles →