Bitter says fast easy runs break runners on high mileage
The ultrarunner and coach says you cannot hold onto quick easy pace and add volume at the same time.
Zach Bitter says the reason strong runners break when they add mileage is simple. They will not slow down on easy days.
"You can't chase high volume and 'fast' easy runs long term," he posted. Once your easy RPE (rate of perceived exertion, how hard the run feels) already represents a high workload, he says, you will get injured if you keep going without pulling back on pace. His line on who this hits is pointed. "That is, imo, why some very talented runners seem to get injured when they dip their toe into high mileage."
That is, imo, why some very talented runners seem to get injured when they dip their toe into high mileage.
The training currency argument
Asked in a reply about easy running being mechanically different from race pace, Bitter said that is a feature rather than a problem. You get the mechanical stimulus specific to race day by doing race pace workouts closer to the race, he says, and you end up doing more quality work overall because you can repeat those sessions more often. The phrase he uses is training currency. Pushing the top end of your low intensity spends it, and then there is less left for the sessions that matter.
His example is marathoner Thomas Nobbs. Bitter says Nobbs runs his easy runs nearly twice as slow as his quality work, which means he shows up to workouts without the mechanical loading that faster easy days would have left in his legs. Bitter says Nobbs has followed that process for a few years and has improved his marathon time at every attempt, from 2:19 down to 2:08.
What it actually means
This is one coach's read, not a study, and the Nobbs case is one runner whose training Bitter is describing from the outside. But the claim is specific and testable against your own log. If your easy pace creeps toward workout pace, Bitter's argument is that you are paying for volume twice, once in the mileage and once in the load each mile carries, and the bill arrives as an injury rather than a bad session.
It also sits neatly alongside the point Bitter and Steve Magness made earlier about the zone 2 fight being overblown. The number on the watch is not the argument. The gap between your easy running and your hard running is.
His easy runs are nearly twice as slow as his quality work.
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