Magness says the zone 2 fight was settled 80 years ago
A fresh round of the easy running argument, and three people who mostly agree with each other.
The zone 2 argument flared up again this week, and Steve Magness's answer was that it was already resolved decades ago.
It started with P.D. Mangan, who posted that "Nothing in exercise science says Zone 2 has unique mitochondrial benefits that higher intensity exercise can't do in far less time," and added that high intensity work has benefits easy running cannot deliver. Magness replied directly, then wrote a longer post making the same case from the history books rather than the lab.
Nothing in exercise science says Zone 2 has unique mitochondrial benefits that higher intensity exercise can't do in far less time.
What Magness actually said
His line is that the sport ran this experiment already. He points to the coaches of the 1940s and 50s, Gosta Holmer, Franz Stampfl, Percy Cerutty, Woldemar Gerschler, Emil Zatopek, and says the pro and anti camps were arguing the same thing then. The sport tried five to six days of intervals, tried long walks as a base, tried all steady. What survived is what shows up in race results.
His conclusion has two halves. One, you need a foundation of lots of easy to steady running, and all intensity cannot replace what that gives you. Two, there is nothing special about zone 2 (the easy aerobic intensity band) specifically, or about any single zone. Some runners do well on very easy work, others on steadier work, and both work with tradeoffs. Once the base is there, you add threshold, VO2 max work, mile pace and real sprints on top.
He blames the framing for the fight. In his words, the problem is that Peter Attia and others turned zone 2 into a very narrow specialized intensity instead of simply saying lots of easy to moderate running.
Bitter on the pile-on
Zach Bitter took a swing at the people celebrating. He posted that most of those doing "I told you so" commentary were never really arguing against zone 2 at all. They were arguing with people who grabbed a trend without understanding that aerobic development happens over years rather than one training cycle.
What it actually means
Nobody in this exchange is against easy running. Mangan is arguing that no narrow intensity band holds a unique mitochondrial claim, Magness agrees that no zone is magic while insisting the easy to steady base is non negotiable, and Bitter thinks the victory lap is aimed at a strawman. If you are training for a marathon, the practical read from Magness is unchanged. Run a lot of easy to steady volume, add harder work on top of it, and do not chase one exact heart rate number as though it unlocks something the rest of your easy running does not.
Magness's caveat for time crunched runners is that more of the easy work needs to be steady, and if you are very short on time, more of it needs to be intense. The base still has to exist.
Most of the people standing on zone 2 grave right now with, "I told you so" type commentary were never truly arguing against it.
There's nothing special about zone 2 or 1 or any zone.
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