Why most of your training should feel easy

Ask a group of amateur athletes how their training feels and most will say "moderately hard" almost every day. Ask the same about Olympic rowers, cross-country skiers or marathoners and you get a very different answer: easy, easy, easy, and then very hard.

When Stephen Seiler reviewed how internationally competitive endurance athletes actually train, the same pattern kept appearing across sports: roughly 80% of sessions done at low intensity, below the first lactate threshold, and the remaining 20% split between threshold work and high-intensity intervals. For an athlete training 10 to 14 times a week, that's only two or three genuinely hard sessions.

Why easy works

Easy aerobic work builds the engine (capillaries, mitochondria, the ability to burn fat at higher speeds) at a low recovery cost. That means you can do a lot of it and still arrive at your hard sessions fresh enough to hit them properly. The trap is the middle: sessions too hard to recover from quickly, but not hard enough to drive the adaptations that intervals do.

Studies comparing intensity distributions back the idea, with honest caveats. A 2014 trial by Stöggl and Sperlich found a polarized plan improved VO2peak and time-to-exhaustion more than threshold-heavy, high-intensity or high-volume plans over nine weeks. A 2024 meta-analysis found the polarized advantage was small and limited to VO2peak, mostly in short programs and highly trained athletes; for race performance, well-structured pyramidal plans did about as well.

So the exact ratio matters less than the principle underneath it: keep your easy days truly easy, so your hard days can be truly hard.