The Physiology of Endurance Running Podcast · Dan Nash and Owain Zerilli

Between Two Thresholds: Everything you need to know about Zone 3

·1 hr 31 min·5 clips

Zone 3 is “a range, it’s a domain, it’s not a discrete point.”

The show opens with a loose check-in and a pretty serious training day. Dan has just come off a 40K day. He reports 5x3K in the morning at roughly 3:05 and 3:04 per kilometer. That sat above marathon pace, but not by much. He then switched gears in the evening and did 3x a mile and 5x a kilometer. The session used 90 seconds of rest throughout. The mile reps came in at 4:49, 4:44, and 4:43. The kilometer reps landed between 2:52 and 2:54. He sounds fairly pleased with that, and the hosts treat it as a strong example of heavy-domain work rather than anything mystical or perfectly tidy. They keep coming back to the idea that zone three is where a lot of controlled training lives. They also acknowledge that people disagree about how to number or label the zone. From there, the discussion moves into LT2 and why heart rate can be more useful than pace in some situations. Pace still matters, especially when you know what a sustainable race pace looks like. But the hosts are blunt that pace is not always the best guide for training. If an athlete has raced a 10-mile or similar event well, that race pace can help define the upper limit. Even then, the point is not to copy the race effort exactly in training. They talk through why race conditions matter. Tapering matters. Carb loading matters. Racing shoes matter. A training run in the dark does not give you the same answer. Heart rate becomes a useful way to keep the effort honest over an hour to an hour and ten minutes. The hosts note that this gets trickier as the race or effort gets longer. They also mention that taking out the first mile or so can help account for heart-rate drift and keep an early spike from skewing the average. The broader point is that all of these labels are useful, but only if they stay tied to real training context. The episode keeps circling back to the same practical idea: most runners probably spend a lot of time in this controlled middle ground, and that is often exactly where steady fitness gets built.

As heard by us

A practical, runner-focused look at the messy middle of threshold training.

This episode sits in the messy but useful middle of endurance running: zone three, heavy intensity, threshold, LT2, and the overlap between them.

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Want zone 3 explained without the lab-coat nonsense?

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