About 600 runners start Leadville each year. By the time the 30-hour cutoff passes, roughly half won't have finished. The DNF list isn't full of unprepared people. Most of them trained. Many have run ultras before. What gets them is specific, predictable, and largely avoidable.
The Altitude Timing Trap
The race starts at 10,152 feet. Hope Pass is at 12,600. At that elevation, aerobic capacity drops roughly 12 to 15 percent compared to sea level.1 Your heart works harder at every pace. What's less talked about: a 2022 study found that this reduction persists even in acclimatized athletes, and is more pronounced in highly trained runners than in recreational ones. Getting fit doesn't get you off the hook.
What most get wrong is the timing. Altitude performance suppression isn't immediate. You may feel fine at the beginning of the race, or even good. But eventually, your plasma volume drops and your resting heart rate climbs.
A 2018 narrative review in Frontiers in Physiology on endurance competition at altitude found that at least two weeks of acclimatization is needed before an athlete can perform at their optimal level at high elevation.2 If two weeks isn't feasible, the same research recommends arriving within 48 hours of the start, sleeping at low altitude if possible, and returning to altitude on race morning. The worst window is arriving two to five days before: enough time for the acute suppression to set in, not enough to begin recovering from it. How quickly you adapt varies. Two weeks is the consensus, not a guarantee.
Hope Pass Will Wreck Your Quads If You Let It
The course crosses Hope Pass twice: outbound from Twin Lakes at mile 40 to the Winfield turnaround, and inbound back at mile 60. The outbound crossing is hard. The inbound one is where your race may end.
The descent back to Twin Lakes on the return drops about 3,200 feet over five miles, at mile 60, on already-taxed legs. Downhill running loads the quads eccentrically, the braking force on the way down, and that causes more muscle damage than the climbing. Runners who haven't trained specifically for descents arrive at Twin Lakes inbound with quads that have basically stopped working. The next 40 miles become a shuffle, if they happen at all. A 2025 review in Sports Medicine surveyed 824 ultramarathon finishers and found that 66% identified muscle breakdown as their primary race impediment — more than aerobic fitness, fueling, or pacing.4 At Leadville, that breakdown has a name and a mile marker: Hope Pass inbound.
Downhill training is its own skill. Controlled effort on 10 to 15 percent grades, built up over weeks, is the only real preparation for Hope Pass. The Iron Miles Training Planner builds descent-specific sessions into mountain terrain plans starting in the Build phase.
Research shows poles reduce quad loading on technical descents, with reductions of 20 to 30 percent in skilled users.3 The caveat: the benefit is technique-dependent. Runners who rarely train with poles don't get the same protection. Most finishers use them on Hope Pass. If you plan to, practice with them on your long runs before race day.
The First 50 Miles Are a Lie
The opening stretch from Leadville to Twin Lakes is mostly runnable. Rolling terrain, nothing that announces itself as hard. Runners see flat miles and run them like flat miles. This is the most common pacing mistake at Leadville.
At 10,000 feet, your heart is working 15 percent harder than it would be at sea level for the same pace. You're not feeling it because there's no steep grade giving you feedback. But you're spending cardiac output that has a fixed balance, and the second half of the race will collect what the first half borrowed.
The runners who finish Leadville consistently report running the first 50 miles feeling like they were holding back too much. That feeling is the plan working.
Add 60 to 90 seconds per mile to your projected pace for the flat sections. Use heart rate, not GPS pace. Your watch will lie to you in the first half.
Nobody Plans for 2am at 11,000 Feet
Leadville days hit 70 to 75 degrees. The return leg, which most runners are on between midnight and 4am, can be 35 degrees with wind. That's a 40-degree swing across a few hours of running.
Runners who end up in trouble on the return leg are frequently the ones who weren't dressed for it. A night gear bag at Twin Lakes inbound (mile 60) should be specific, separate from everything else, and ready to hand off in under two minutes. Not mixed in with other supplies. Not something your crew has to search for while you stand there getting cold.
Your Crew Needs a Written Plan
Leadville has seven crew access points. Winfield has a one-way road and limited parking. Fish Hatchery has specific lot access. Most crews figure this out in real time, which means late arrivals, wrong bags, and runners waiting at aid stations instead of moving through them.
A handoff that takes five minutes instead of two doesn't sound like much. At mile 65, depleted and cold, it can be the difference between getting back out and sitting down.
The 2026 Leadville Trail 100 is August 22. You can find the full race listing, registration link, and hotel booking for Leadville in the Iron Miles race directory.
Map Your Leadville Crew Logistics
The Iron Miles Race Planner builds crew briefing sheets with access points, timing windows, and task lists for every stop. Build it once, share it with your crew.
Build Your Race PlanWhat the Finishers Do Differently
The finishers aren't a different type of runner. They managed arrival timing deliberately. They ran the first half slower than felt right. They trained descents, not just climbs. And they sent their crew a written plan, not just a verbal briefing the week before.
None of that is fitness. It's preparation. And it's all stuff you can do.
Build a Leadville-Specific Training Plan
The Iron Miles Training Planner includes altitude warnings for high-altitude races, descent-specific sessions for mountain terrain starting in Build, and race nutrition practice baked into long run labels from week three. If you're building toward Leadville, start here.
Build My Training Plan- Pühringer R, Gatterer H, Berger M, Said M, Faulhaber M, Burtscher M. "Does Moderate Altitude Affect VO2max in Acclimatized Mountain Guides?" High Altitude Medicine & Biology. 23:37–42, 2022. doi:10.1089/ham.2021.0081. Found that VO2 max reduction at altitude persists even after acclimatization and is more pronounced in highly trained athletes.
- Millet GP, et al. "Preparation for Endurance Competitions at Altitude: Physiological, Psychological, Dietary and Coaching Aspects. A Narrative Review." Frontiers in Physiology, 2018. PMC6218926. "An acclimatization period of at least 2 weeks seems to be necessary before being able to compete at the optimal level in a high-altitude endurance event." Minimum recommended arrival: 42–52 hours before competition.
- Stoggl T, et al. "Biomechanical comparison of running with and without trekking poles on hilly terrain." Journal of Human Kinetics, 2016. Pole use reduced quadriceps loading on descents by 20–28% in mountain running conditions.
- Tiller NB, Millet GY. "Decoding Ultramarathon: Muscle Damage as the Main Impediment to Performance." Sports Medicine, 55(3):535–543, 2025. doi:10.1007/s40279-024-02125-z. Survey of 824 finishers; 66% identified muscle breakdown as their primary race impediment, ahead of aerobic capacity, running economy, and GI distress.