Zone 3 has a reputation problem. Some coaches call it the grey zone — too hard for recovery, not hard enough for maximum stimulus. And when Zone 3 happens by accident, drifting up from what should have been a Zone 2 session, that criticism is fair.

But the athletes who dismiss Zone 3 entirely are missing one of the most time-efficient tools in training: sweet spot intervals, deliberately executed at the top of Zone 3 for extended durations.

In this episode, Coach Chris breaks down the crucial difference between grey zone grinding and intentional sweet spot training, and why that distinction changes everything.

At sweet spot intensity — the upper edge of Zone 3 into the very bottom of Zone 4 — your body can use lactate as a direct fuel source. You're training your Type IIa muscle fibres to become more aerobically efficient. And you can sustain this intensity for 20 to 60 minutes, creating extended adaptation time that Zone 4 intervals simply can't match.

You'll learn two formats that actually work: long sustained sweet spot intervals, starting at 2×20 minutes and building toward a single 60-minute effort, and over-under intervals — the structure used by athletes like Tadej Pogačar that alternates just below and just above threshold to train lactate clearance directly.

Plus: how often to do this, how to structure recovery around it, and the one mistake that turns a great sweet spot session into wasted fatigue.

Book your free No-Sweat Intro at catalystgym.com/free-intro.