Running Plan Review Koerner Ultra: 100 Miles
By Hal Koerner: Field Guide to Ultrarunning — Hal Koerner Requires purchase Visit plan website
Plan at a Glance
A hundred miles is a different kind of problem. It is not run fast enough for speed to matter, and it runs long enough that fueling and durability decide everything. Hal Koerner's plan answers that honestly. It drops speed work almost entirely and spends twenty weeks building a huge aerobic base and the biggest back-to-back long runs of any plan he writes.
Koerner is a two-time Western States 100 champion and a Hardrock winner, a hundred-mile specialist who has finished over 130 ultras. This is his longest and most demanding build, twenty weeks at six days a week. There are no fartleks or tempos here. The work is easy miles and, on the weekends, long runs that climb to a 35 with a 20 behind it and a 25 backed by another 25.
It suits a seasoned ultra runner with a big base and the time this asks for. Everything is miles and effort, never pace, because at a hundred miles pace is beside the point. The running is the smaller half of the task. The fueling, crewing and race management that carry you through a night and a day are all in the book.
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When you step up to a hundred miles, this is a serious and specific build that will look monotonous because it is meant to. There is almost no speed work. You spend twenty weeks running easy miles and, every weekend, long runs on tired legs.
That plainness is the point. A hundred-mile race is not won by being fast. It is won by not falling apart, and by eating and drinking well enough to keep going for a day or more, so the plan trains durability above all. The back-to-back weekends are the biggest Koerner writes. A 35-mile Saturday is backed by a 20 on Sunday, or a 25 pairs with a 25. Nothing rehearses the last stretch of a hundred like running long on spent legs. The load is huge but steady, with cutback weeks so the biggest weekends land on prepared legs.
Judged as a fitness plan it is sound, if unavoidably a grind. Its real risk is what it does not put on the calendar. At a hundred miles, fueling and crewing are not support acts. They are the event, and both live in the book, not the schedule. Read those chapters as the other half of your training. A hundred-miler is lost to a bad stomach or a missed drop bag far more often than to missing miles.
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Structure
Does the plan build you up smartly?
Partly. The twenty weeks build steadily and carry cutback weeks, but the phases are unnamed and the rhythm is uneven. Because there is no intensity, the plan is mostly a rising line of mileage rather than a shaped progression. It brings you to the line fit, but the structure is plain by design more than by craft.
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Prevention
Does the plan protect you from injury?
Mostly, given how the load is built. The mileage rises in gentle steps, and even the huge back-to-back weekends arrive gradually, with cutback weeks between. The catch is the sheer volume, since peak weeks near the mid-seventies on a hundred-mile runner's legs leave little margin. Strength and warm-ups are book topics, not scheduled sessions.
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Flexibility
What happens when you miss a day?
This is the plan's strongest suit. Every run is miles and effort with no pace to miss, so a flat day simply runs slower, which over twenty weeks you will need often. Koerner's setback rule is explicit: scale a day to the fraction of normal you feel, watch your resting heart rate, and trust that fitness holds about two weeks. A missed week is one you ease back from, never cram.
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Readiness
Will the plan deliver race-day fitness?
Mostly, for the distance's own demands. The enormous back-to-back long runs rehearse running on deep fatigue, which is most of what a hundred miles asks. What is missing is any sharpening, since there is no faster work to lift your cruising gear, so you arrive durable but not quick. For a competitive hundred that can cost you; for simply finishing, the endurance is what counts.
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Variety
Are the workouts varied enough?
Not really, and that is deliberate. The plan is easy miles and long runs, with no fartlek, hills or tempo at all. A hundred-mile race barely rewards speed, so Koerner spends every session on endurance instead. It makes for a monotonous build, durable and specific and undeniably a grind.
Plan Strengths
- The biggest back-to-back long runs Koerner writes, a 35 and a 20 and a 25 with a 25, rehearse the deep fatigue of a hundred miles.
- Twenty weeks of mostly easy running build the enormous aerobic base the distance is run on.
- Cutback weeks are spaced through the build, so even the heaviest weekends land on prepared legs.
- Miles and effort drive everything, with no pace to chase, which is right for a race this long.
- Koerner's setback method is explicit, which matters over a build this long where something always goes wrong.
Weaknesses & gaps
- Fueling and crewing decide a hundred-miler, yet both are book chapters rather than scheduled parts of the plan.
- It carries no speed work at all, so you arrive durable but without a sharper cruising gear.
- The build is a long grind of similar weeks, which asks real patience to see through.
- Peak volume on a hundred-mile runner's legs leaves little margin, demanding honest day-to-day self-monitoring.
What this plan does not give you
At a hundred miles the plan's omissions are the race itself. Fueling and hydration are the event as much as the running, and Koerner's numbers have to be part of your training, not left on the page. Crewing, pacers, drop bags and managing a night on the trail are all in the book and are not optional at this distance. Strength work is described but never scheduled, so add a little on easy days. And there is no tune-up, though a 50-miler or 100K in the build is the only honest way to rehearse the whole operation before the day itself.
What the science supports
Easy miles do most of the work
Almost every mile in this plan is easy, and that is the entire design. A hundred miles is run far below your hard efforts, so the deep, patiently built aerobic base is what actually carries you. The research on runners is consistent that a base weighted toward easy running outlasts one padded with hard miles. Here it is not most of the training; it is nearly all of it.
Haugen et al. 2022; Casado et al. 2022; Tønnessen et al. 2014
Tendons adapt slower than muscle
Twenty weeks is a long build, and the length is deliberate. Tendons and bones toughen under running load far more slowly than muscle does, and a hundred-mile body has to hold together for a very long day. Stretching the plan out, and reaching the biggest weekends only late, gives that slow connective tissue the months it needs to adapt.
Werkhausen et al. 2019; Marqueti et al. 2019; Devaprakash et al. 2020
Higher weekly mileage lowers injury risk
Weekly mileage climbs toward the mid-seventies before the taper. Built up gradually, higher running volume is linked to lower injury risk and better durability, not the breakdown you might fear. For a race that punishes any weak link over a hundred miles, that slowly earned load is the toughness the distance demands.
Individualized plans beat one-size-fits-all
Because each run runs on effort rather than a fixed pace, you fit the plan to yourself and to the day, the terrain and how the legs feel. Training shaped to the runner tends to work better than a rigid template, especially across a twenty-week build where no two weeks feel the same. The plan hands you that adjustment, and Koerner's setback rules tell you how to use it.
Nuuttila et al. 2022; Vesterinen et al. 2016; Javaloyes et al. 2019
Long runs are essential for the marathon
The back-to-back long runs are the whole plan, and rightly so. Endurance for a hundred miles is built by long running and cannot be faked with anything shorter. Running a 20-mile Sunday on the wreckage of a 35-mile Saturday is the most race-specific training a hundred-mile plan can offer, the closing miles of the race rehearsed in advance.
Toresdahl et al. 2021; Jones & Kirby 2025; Casado et al. 2019
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Frequently asked questions
- Is Koerner Ultra: 100 Miles good for beginners?
- No. Koerner Ultra: 100 Miles is built for advanced-level runners. A true beginner should start with a lower-mileage plan.
- How many days per week does Koerner Ultra: 100 Miles require?
- The plan runs on a schedule of multiple weekly runs. See the at-a-glance strip for the exact count.
- Does Koerner Ultra: 100 Miles include a taper?
- Yes, the plan includes a taper into race week.
- What is the rubric grade for Koerner Ultra: 100 Miles?
- Koerner Ultra: 100 Miles grades D on the Buena Vida rubric.