Guest post by Chris Beavon, RunLab Media
Preparing your legs for the steep eccentric loading of downhills in an ultramarathon is an important part of the picture. But it may not take as much work as you think. One of the most well-established phenomena in exercise science is the repeated bout effect, which means that more downhill running isn’t necessarily more beneficial.
I’m an amateur runner and one half of RunLab Media, the YouTube channel I host with Vlad, an elite trail runner. In this week’s video, we explored the RBE and discussed how to structure downhill sessions into your training build.
Contents
Why one session does so much
Downhill running loads the muscles in a specific way called eccentric contraction. They lengthen while bracing under force, instead of shortening to push you forward. That’s what makes your quads sore for days after a big descent, and it’s also what triggers a protective adaptation in the muscle.
The body lays down structural, neural, and inflammatory changes off one hard session that make the second exposure substantially less damaging. The protection peaks within a few weeks and persists for up to six. After that it tapers off.
This is different from how your cardiovascular system adapts. Building VO2 max or aerobic capacity needs consistent weekly loading. Eccentric protection works the opposite way: more frequent sessions bring diminishing returns on the protection itself, while still adding fatigue and injury risk.
The protocol
A simple four-piece structure that fits any ultra build with significant descent, all of it anchored to the six-week protection window.
- Primer session, 10 to 12 weeks before race day. 20 to 30 minutes of cumulative downhill at a gradient that meaningfully loads the eccentric chain. The session that triggers the adaptation. Plan to be sore for 3 to 7 days afterwards, particularly the first time.
- Maintenance, every 3 to 4 weeks across the build. 4 to 6 reps of 90-second downhill efforts at moderate-hard pace. If you live somewhere mountainous and your long runs already include significant descent, those can serve the maintenance purpose without a dedicated session.
- Optional race-specific session, 4 weeks out from race day. Useful for mountain-heavy races. Another primer-style 20 to 30 minute cumulative downhill effort, late enough to be specific to race demands, early enough to recover and taper.
- Taper window, final two weeks. No downhill work. The protection you’ve already laid down will hold through race day, and new eccentric damage recovers slowly.
RunMotion’s 100km trail training plan builds these in for you if you don’t want to programme them yourself.
Every 3 to 4 weeks is where we’ve landed for maintenance sessions, though some coaches advocate for a more frequent cadence at every 2 to 2.5 weeks. Both fall inside the six-week protection window, so either works. The choice comes down to how much fresh eccentric load your week can absorb without compromising the rest of your training.
For runners with regular access to hilly terrain, the question is largely moot. Long runs over rolling country will deliver maintenance-level descending without needing a dedicated session.
If your terrain doesn’t cooperate
If you’re training for a mountain ultra without mountain access, the cleanest substitute is a training camp 3 to 5 weeks before race day, somewhere with the gradient you’ll race on. Two or three sessions over a long weekend lay down the protection, and you ride it through to race day.
If a camp isn’t possible, the next-best substitution is heavy eccentric strength training built into your year-round block: weighted step-downs, slow-tempo Bulgarian split squats, single-leg Romanian deadlifts. Not a perfect substitute for the running, but it loads the same muscle groups in the same lengthening pattern. RunMotion’s trail-specific training plans include this strength layer alongside the running.
What to avoid
Three places the protocol can drift off course:
- Stacking downhill sessions weekly. Once the first session has triggered the adaptation, more frequent exposure brings diminishing returns on protection while still adding fatigue.
- Treating maintenance sessions like full primer sessions. Maintenance is meant to keep the adaptation active, not to maximally damage the muscle a second time. Save the bigger effort for the primer.
- Doing downhill work in the last two weeks before race day. The protection you’ve already laid down will hold. New damage in taper is expensive to recover from and may add little protection beyond what’s already there.
The principle is simple: one hard bout protects you for weeks. Stick to the protocol, and put the time you’d otherwise spend on extra downhill sessions somewhere more useful.
The full video is over on the RunLab Media YouTube channel: Vlad’s descent coaching, the three hard reps, and the post-session conversation about how to programme this into your year. For the full evidence base and references behind the protocol, the companion doc is on the RunLab site.
RunMotion is an adaptive coaching platform that incorporates hills to make you stronger. Plans flex around real life and your goals, so the work you put in on climbs like this one actually shows up in your race.