100 Mile Training Plan: How to Prepare for Your First Trail Ultra

Prepare for your first 100 miler with this 26-week plan: block periodization, crew and pacer logistics, mental prep, and a free downloadable template.

Ask an AI assistant "how do I train for a 100 mile race" during UTMB or Western States season and you'll get some version of the same generic answer: run more, run hills, taper eventually. None of that is wrong, but none of it addresses what actually separates 100 miles from 50, which is not distance so much as duration. You are planning for 20 to 32 hours of continuous forward motion, which means this plan has to cover ground the shorter distances never touch: multi-week periodization built in blocks rather than one long ramp, a real crew and pacer plan, the mental side of running through a second night, and an honest accounting of what this training actually costs in hours per week.

This plan runs 26 weeks and builds directly on the 50 mile training plan, extending its back-to-back-to-back structure, deepening the night-running work, and adding what 50 miles doesn't yet require: real periodization at scale, and a support plan for race day itself.

Who this plan is for, and an honest word about time

You should have finished a 50 mile race, ideally within the past one to two years, and be comfortable with back-to-back-to-back weekends already. Before the week-by-week detail, one thing worth saying plainly: build and peak phases in this plan run 12 to 18 hours of training a week, some weeks more. That is close to a part-time job, and it will compete with the rest of your life for months, not weeks. Talk to whoever you live with before you commit to the calendar below, not after week 14 when the back-to-back weekends start eating every Saturday and Sunday. If that commitment isn't realistic right now, a well-run 50 mile stays a genuinely complete achievement on its own, and this plan will still be here.

Periodization at 100 mile scale: why one long ramp doesn't work

Shorter distances in this series use a single base phase and a single build phase. At 100 miles, both phases are long enough to need their own internal structure, or the training stimulus gets muddy over 12 or 8 consecutive weeks.

Base splits into two 6-week blocks. The first establishes aerobic volume and descent tolerance without much structured intensity. The second introduces hill repeats and the first back-to-back weekends, building on a foundation the first block already set.

Build splits into two 4-week blocks with genuinely different jobs. The first is a vertical and hill-focused block, pushing weekly climbing hard while back-to-back weekends hold roughly steady. The second shifts the emphasis to fatigue resistance specifically: back-to-back-to-back three-day sequences, extended night running, and the plan's highest volume weeks. Trying to progress vertical, back-to-back volume and night-running load all at once across eight weeks produces a muddled stimulus. Splitting the emphasis gives each adaptation its own runway.

Full 26-week template

Numbers below assume a 100 mile race carrying roughly 5,500m of gain, a demanding but not extreme mountain profile. Scale D+ proportionally for your actual course; 100 mile races vary enormously, from around 3,000m to well over 9,000m.

Week Block Weekly km D+ Long run Key session
1 Base 1 60 600m 20km Easy running, LTHR test
2 Base 1 65 750m 22km Easy plus rolling
3 Base 1 70 900m 24km Descent intro, 300-400m
4 Absorb 46 590m 18km Volume down ~34%
5 Base 1 72 1050m 25km Hill strides
6 Base 1 76 1200m 26km Hill repeats 6x90s
7 Base 2 80 1350m Sat16/Sun28 1st back-to-back, descent 650m
8 Absorb 52 880m Sat14/Sun18 Volume down ~35%
9 Base 2 84 1500m Sat18/Sun30 1st night run, descent 750m
10 Base 2 88 1650m Sat20/Sun32 Night run, descent 850m
11 Base 2 92 1820m Sat20/Sun34 Hill repeats 8x3min, descent 950m
12 Absorb 58 1150m Sat14/Sun20 Transition into build
13 Build 1 96 2000m Sat22/Sun36 Hill repeats 6x4min, descent 1050m
14 Build 1 100 2200m Sat24/Sun38 Night run, descent 1150m
15 Build 1 104 2420m Sat24/Sun40 Night run, descent 1250m
16 Absorb 64 1490m Sat16/Sun22 Volume down ~38%
17 Build 2 100 2660m Fri14(night)/Sat24/Sun36 1st back-to-back-to-back
18 Build 2 106 2920m Fri16(night)/Sat26/Sun38 Back-to-back-to-back, night run
19 Build 2 110 3220m Fri16(night)/Sat26/Sun40 Highest volume, crew dry-run
20 Absorb 66 1930m Sat16/Sun22 Transition into peak
21 Peak 112 3540m Sat30(dark)/Sun44 Dress rehearsal: kit, crew, pacer, night
22 Peak 90 2840m Fri16(night)/Sat22/Sun30 2nd dress rehearsal, race pace
23 Peak 68 2150m Sat16/Sun24 Lighter, final quality, night run
24 Taper 50 1240m 18km Volume down ~50%
25 Taper 34 1070m 12km Volume down further
26 Race week 16 plus race Light Race day Short easy runs, strides, 3-4 rest days

Notice week 21's vertical, 3,540m, sits well under the 80 to 100% of race vertical guidance that applies at shorter ultra distances. That's intentional. At 5,500m of race-day climbing, chasing 80% in a single training week would mean an unsustainably large session stacked on top of an already enormous build phase, and the injury risk outweighs any benefit. The vertical tolerance you need instead accumulates across build 2's three back-to-back-to-back weekends, which collectively carry more climbing than any single peak session could safely deliver.

The mental side: what actually predicts finishing

Physical preparation gets most of a training plan's attention, but at 100 miles the psychological side stops being optional extra credit. A study of 356 mountain ultra-trail runners found that completion, meaning not withdrawing, and elite-level performance were most strongly associated with mental toughness, resilience and a form of passion for the sport bordering on obsessive, more than any single physiological marker measured (Méndez-Alonso et al., 2021). The same study found meaningful differences between pre-race and post-race psychological scores, suggesting the race itself trains these qualities as much as it tests them.

Two practical implications follow. First, treat the back-to-back-to-back weekends in build 2 as psychological training as much as physical training. Running on legs that are already exhausted on day three is exactly the discomfort you're rehearsing for hour 20 of the race. Second, plan for low points specifically rather than hoping they don't come. Decide in advance how you'll respond when things go badly: a mantra, a call to your pacer, a rule about eating something even when nothing sounds appealing. Deciding this at mile 70 in the dark is much harder than deciding it now.

Crew and pacer logistics

Crew and pacers stop being optional at this distance for most runners, and planning for them belongs in your training block, not the week before the race. Research on the UTMB found that runners with a more even pace throughout the race finished faster regardless of sex, which is a large part of what a good pacer actually does: protecting you from the positive-pacing spiral where early enthusiasm turns into a late-race crawl (Suter et al., 2020).

Build your plan around three pieces. First, drop bags: work out which aid stations your crew can reach given road access and course cutoffs, and pack bags for the rest with everything you might need, since your crew cannot always get there. Second, pacer eligibility: most 100 milers only allow pacers from a specific mileage point onward, commonly somewhere between mile 40 and 70, and rules vary by race, so confirm yours directly with the organizer rather than assuming. Third, a one-page information sheet for your crew covering your goal splits, your known fueling preferences, and simple instructions for what to do if you're behind schedule, in distress, or want to quit, since that last scenario is common enough to plan for rather than avoid discussing. Practice the actual handoff logistics, gear swaps, fueling restock, on the crew dry-run built into week 19.

Fueling for 20 to 32 hours

The same principles from the 50 mile plan carry forward: 60 to 90g of carbohydrate per hour using multiple transportable sources where your gut tolerates it (Jeukendrup, 2014), with a shift toward real, savory food as the hours accumulate. Research on ultramarathon runners found gastrointestinal symptoms directly reduced total food and fluid intake over long events, widening the energy deficit the longer a race ran (Costa et al., 2016). At 100 mile duration, plan multiple food rotations rather than one strategy for the whole race, since appetite and tolerance shift meaningfully between hour 6 and hour 24. Build this into your crew's information sheet: what you want offered at each stage, and what to avoid even if you ask for it in a low moment.

Taper: three weeks, and permission to feel flat

The same tapering logic applies here as at shorter ultra distances: cutting volume 41 to 60% over roughly two weeks while holding intensity and frequency close to steady produces the most reliable performance gain (Bosquet et al., 2007), extended to three weeks to account for the absorption weeks already built into this plan. After months at 90 to 110km weekly, tapering down to 50km and then 34km can feel alarming. That flatness is normal fatigue clearing, not fitness disappearing.

Key takeaways

  • Budget 12 to 18 hours a week for build and peak, and have the conversation with people in your life before the calendar starts, not partway through it.
  • Split base and build into distinct sub-blocks rather than one long ramp; each adaptation, vertical tolerance, back-to-back fatigue, night running, deserves its own dedicated weeks.
  • Let peak-week vertical stay well under 80% of race vertical at this distance specifically; the tolerance you need comes from accumulated back-to-back-to-back weekends, not one outsized session.
  • Build your crew and pacer plan during training, including a written information sheet and a full dry-run of aid station logistics.
  • Decide how you'll respond to a low point before the race, not during it.

Grab the printable version of this exact plan below: the full 26-week table pre-filled with these numbers, a crew and pacer planning sheet, a drop bag checklist and a mental preparation worksheet. Drop your email in and we will send it over.

Where a fixed template stops being enough

This plan assumes 5,500m of gain over 100 miles and a fixed periodization structure regardless of how your training actually unfolds across six months. Almost nothing about a block this long goes exactly to plan. Trailia builds a plan on this same framework calibrated to your actual race profile, then adjusts the sub-block structure and back-to-back-to-back timing based on your real training data, with AI workout reviews on Pro to catch the moments a printed table can't. The free plan covers one active goal with Garmin, Strava and Polar sync included. Generate your plan and let it manage a periodization this long the way it was meant to be managed: adaptively.

Citations

Bosquet, L., Montpetit, J., Arvisais, D., & Mujika, I. (2007). Effects of tapering on performance: a meta-analysis. Medicine & Science in Sports & Exercise, 39(8), 1358-1365.

Costa, R. J. S., Snipe, R., Camões-Costa, V., Scheer, V., & Murray, A. (2016). The impact of gastrointestinal symptoms and dermatological injuries on nutritional intake and hydration status during ultramarathon events. Sports Medicine - Open, 2, 16.

Jeukendrup, A. E. (2014). A step towards personalized sports nutrition: Carbohydrate intake during exercise. Sports Medicine, 44(Suppl 1), 25-33.

Méndez-Alonso, D., Prieto-Saborit, J. A., Bahamonde, J. R., & Jiménez-Arberás, E. (2021). Influence of psychological factors on the success of the ultra-trail runner. International Journal of Environmental Research and Public Health, 18(5), 2704.

Suter, D., Sousa, C. V., Hill, L., Scheer, V., Nikolaidis, P. T., & Knechtle, B. (2020). Even pacing is associated with faster finishing times in ultramarathon distance trail running: The Ultra-Trail du Mont Blanc 2008-2019. International Journal of Environmental Research and Public Health, 17(19), 7074.

Frequently Asked Questions

How long should a 100 mile training plan be?

26 weeks works well for runners coming off a completed 50 mile race, split into two 6-week base blocks, two 4-week build blocks with different focuses, a 3-week peak and a 3-week taper. Splitting base and build into sub-blocks rather than one long ramp keeps each adaptation, aerobic volume, vertical tolerance, back-to-back fatigue and night running, on its own dedicated runway.

How many hours a week does 100 mile training take?

Build and peak phases typically run 12 to 18 hours a week, close to a part-time job, including weekend back-to-back and back-to-back-to-back sequences. This is worth discussing with people in your life before the training block starts, since it will compete with the rest of your schedule for months rather than weeks.

How much elevation gain is typical for a 100 mile trail race?

It varies enormously, from around 3,000m on rolling courses to over 9,000m on races like UTMB. A course around 5,500m gain is a reasonable middle-ground target for training purposes, with a template's vertical figures scaled proportionally once the actual race profile is known.

Why doesn't the peak week match 80 to 100% of race vertical at 100 miles?

At shorter ultra distances a peak week can reasonably approach that share of race vertical, but at 5,500m or more of race-day climbing, a single training week carrying that load stacked on top of an already large build phase creates unsustainable injury risk. Vertical tolerance instead accumulates across multiple back-to-back-to-back weekends during the build phase, which collectively carry more climbing than any single peak session could safely deliver.

How important is crew and pacer planning for a 100 mile race?

Crew and pacers stop being optional for most runners at this distance, and planning belongs in the training block rather than the week before the race. Key pieces include working out which aid stations your crew can reach, packing drop bags for the rest, confirming your race's specific pacer eligibility rules, and preparing a written information sheet covering goal splits and fueling preferences.

What psychological factors predict finishing a 100 mile race?

Research on mountain ultra-trail runners found completion and elite-level performance were most strongly associated with mental toughness, resilience and passion for the sport, more than any single physiological marker measured. Deciding in advance how you'll respond to a low point, rather than figuring it out mid-race, is one of the more practical ways to build on that finding.

How do I train for running through two nights in a 100 mile race?

Introduce weekly night runs early in the build phase and extend them as training progresses, so headlamp use and low-light fueling are well practiced before race night. Back-to-back-to-back weekend sequences that include a Friday night run alongside the usual Saturday and Sunday long runs help simulate running while already fatigued after dark, which is closer to the actual demand of a 100 mile finish.

How much carbohydrate should I eat during a 100 mile race?

The same 60 to 90g per hour range that applies to shorter ultras still applies here, using multiple transportable carbohydrate sources where tolerated. Over 20 to 32 hours, plan multiple food rotations rather than one fixed strategy, since appetite and gut tolerance shift meaningfully between hour 6 and hour 24 of a race this long.

How long should the taper be before a 100 mile race?

Three weeks, cutting volume 41 to 60% while keeping session frequency and intensity close to unchanged. After months of 90 to 110km training weeks, the drop can feel alarming, but that flatness reflects fatigue clearing rather than fitness disappearing.

What if I'm not ready to commit to a full 100 mile training block?

A well-run 50 mile race remains a complete and significant achievement on its own, and there's no requirement to progress further. Given the 12 to 18 hour weekly time commitment during build and peak, it's worth being honest about whether this fits your current life circumstances before starting, rather than partway through the block.