THE SHORT ANSWER
Ask Seiler what Zone 2 is for and he won't give you a heart-rate number first — he'll talk about restraint. The single biggest mistake he sees amateurs make is riding their easy days too hard, which quietly wrecks the quality of the hard days. Genuine Zone 2 is conversational: you can talk in full sentences, grab a coffee mid-ride, and finish feeling like you could do it again tomorrow. He's also clear that power alone misses it — heart rate, RPE and a sub-2 mmol/L lactate all tell you more about whether today's easy is actually easy, because heat, sleep and stress move the number around. Build the aerobic base patiently and everything stacked on top of it works better.
WHO IS STEPHEN SEILER?
Stephen Seiler's research helped turn endurance-training intensity distribution into a measurable question. His 2010 review described an approximate 80/20 pattern by sessions among high-volume competitive athletes, while later research shows both pyramidal and polarised distributions. Roadman uses that evidence with its denominator and population intact instead of presenting 80/20 as a universal law.
SEILER ON ZONE 2
Seiler’s key positions on Zone 2 training.
- Polarised training: ~80% of sessions at low intensity, ~20% at high intensity, very little time in the threshold/tempo grey zone.
- Long, slow distance is the irreplaceable foundation — high-intensity work without an aerobic base produces short-lived gains.
- Heart rate, RPE, and lactate at sub-2 mmol/L are all reliable markers for genuine Zone 2 — power alone misses the day-to-day variation.
IN SEILER’S OWN WORDS
Verbatim from Stephen Seiler’s appearances on the podcast.
“what we've seen that across Sports we've collected data from some of the best performers in the world in running in CrossCountry skiing in cycling and Rowing and so there's a bit of a universality to this that they're roughly doing about eight out of 10 sessions training sessions are essentially low stress days they're doing lots of work but they're keeping the lactate low they're in that green zone and then two to three days a week or sessions out of 10 are the more high stress”
“I do not know of data that has been published and subjected to peer review that shows that doing recovery rides accelerates recovery compared to sitting on the sofa. if you're really tired I say take a rest day meaning an actual rest day where you don't ride people are scared to death of that but they shouldn't be”
“the really good endurance athletes they may be cruising along at .7 Millar lactate whereas the average person is at 1.8 you know so they are really able to work with very low you know low turnover of lactate and so that may be you may be saving them glycogen basically”
“What I saw is that athlete populations from diverse sports that really weren't talking to each other or independent of each other finding the same solution to a problem to a biological challenge.”
HEAR IT ON THE PODCAST
Episodes where Stephen Seiler covers Zone 2 training and related ground.
FREQUENTLY ASKED
What does Stephen Seiler say about Zone 2 training?
Ask Seiler what Zone 2 is for and he won't give you a heart-rate number first — he'll talk about restraint. The single biggest mistake he sees amateurs make is riding their easy days too hard, which quietly wrecks the quality of the hard days. Genuine Zone 2 is conversational: you can talk in full sentences, grab a coffee mid-ride, and finish feeling like you could do it again tomorrow. He's also clear that power alone misses it — heart rate, RPE and a sub-2 mmol/L lactate all tell you more about whether today's easy is actually easy, because heat, sleep and stress move the number around. Build the aerobic base patiently and everything stacked on top of it works better.
What is Seiler's main point on zone 2?
Polarised training: ~80% of sessions at low intensity, ~20% at high intensity, very little time in the threshold/tempo grey zone.
Which Roadman Cycling Podcast episodes cover Stephen Seiler on zone 2?
Seiler discusses Zone 2 training in these episodes: "Professor Seiler Returns — What Has Changed | Roadman Cycling Podcast", "Secret To Cycling Fast At A Low Heart Rate | Prof Seiler", "80/20 Training to Ride Faster | Dr Stephen Seiler".