If you've ever wondered why Anthony talks about Zone 2 the way he does — why "ride your easy days easier" comes up in almost every coaching conversation on the podcast — the answer is Stephen Seiler.
Seiler is the exercise physiologist who, working from his lab at the University of Agder in Norway, did the work that turned a coaching hunch into a measured pattern. He pulled training data from elite cyclists, rowers, cross-country skiers, and middle-distance runners across multiple countries and asked a simple question: what does the intensity distribution actually look like? The answer was the same across every sport: roughly 80% of sessions at low intensity, 20% at high intensity, very little time in the threshold or tempo middle ground. That pattern is now known as polarised training, and the rough split is now known as the 80/20 rule. Both terms originate with him.
For a serious amateur rider, the practical takeaway is harder than it sounds. You probably already know intervals matter. What you might not know is that the easy work between them matters more — and that "easy" almost certainly means easier than you currently ride it. Seiler's lab work makes a clean case that the riders who plateau at the same FTP year after year are usually the ones drifting their endurance rides up into tempo. They're not lazy. They're working too hard on the wrong days.
That is the position the rest of Roadman builds on. The Zone 2 explainer, the polarised vs sweet spot comparison, the FTP plateau diagnostic — they all sit on top of his research. When Anthony tells you the easy ride needs to be 60–75% of FTP, conversational, fully aerobic, that's Seiler's lactate-threshold work translated for the bike.
Two podcast episodes with Anthony cover the framework directly. Both are worth your time before you tweak another training plan.