Albertus Roux is a sports scientist and ultra-trail runner specialising in endurance performance and human physiology. Drawing on scientific research, coaching experience, and years of ultra-distance mountain running, his work focuses on resilience, discipline, and the mental and physical demands of endurance sport. He helps athletes improve performance and unlock long-term potential through evidence-based insight and real-world experience.
By Albertus Roux
One of my first trail races was the Langeberg Skyrace in Robertson, not far from where I grew up. The course climbs to the top of Arangieskop — a brutal ascent of 1,900 meters over 22 kilometers, with most of the climbing condensed into one massive spike.
Back then, I thought my climbing ability was pretty decent for my training age, so I stormed up the mountain with all the bravado I could muster. I reached one of the most spectacular peaks in the Langeberg range well within the top 20.
But on the descent, I learned firsthand the real importance of downhill running. One by one, runners streamed past me as I fought to stay upright, my legs turning to concrete. I simply didn’t have the technical skill or the muscular resilience to hold my pace — and after overreaching on the climb, I’d already dug my own grave.
Looking back, I know I could have performed far better if I had varied my effort earlier and trained specifically for the eccentric demands of downhill running.
If you’ve ever run an ultramarathon, you would know how crucial pacing is. It can make or break your race. Mistakes early in the race like charging too hard on the first climb, can come back to haunt you later in the race.
Recent research has taken a deep look into this topic, to see what the best athletes are doing, and where athletes lose time. The good news? Science gives us clear, trainable strategies that can give us statistical pacing advantages on race day.
Breaking down the demands of trail running
Trail running consists of four disciplines: level running, uphill running, downhill running, and walking (commonly called power hiking). Each place different demands on the body and should be seen in isolation in order to train each in its own right. In this post, we’ll look at how two of these disciplines play a role during racing, and how you can train to improve them.
What the Research Says About Ultra Trail Pacing
Over the past few years, researchers have explored the pacing strategies of runners in some of the biggest races on the calendar.
Genitrini et al. (2022) analysed data from over 1600 athletes across multiple editions of UTMB, CCC, and Javelina 100k and 100mi races. They found that faster finishers ran downhill sections at a faster relative pace and uphill sections at a slower relative pace than slower finishers. Runners slowed more on downhills than uphills as the race went on. Limiting performance decline in downhill running leads to faster finish times.
De Waal et al. (2025) observed 50 participants of the 2021 Ultra Trail Cape Town 100km race. They identified 46 Strava segments on the route, therefore 2261 individual segments were analysed when excluding incomplete GPS data. They found that relative uphill pace had a better relationship with race performance than level or downhill running. In other words, what you did on the uphills had the most impact on your race time. Faster finishers started the race at a slower relative pace than slower finishers, and they slowed down much more gradually than slower finishers.
Corbí-Santamaría et al. (2023) included over 5000 participants of four editions of the Orsières–Champex–Chamonix (OCC) 56.3km. Their findings showed that faster finishers varied their pace more, slowing on climbs and speeding up on descents. Faster finishers vary their pace during the race to have a more constant oxygen consumption (VO2), optimising metabolic expenditure.
In other words, they change their pace to keep the effort more evenly balanced across the race. Trail running differs from road running, as stable and consistent pacing is better for road performance, whereas variable pacing is better for trail performance.
Uphill vs Downhill: How Each Impacts Performance
It seems apparent that both uphill and downhill running are key to overall race performance, but for very different reasons. Uphill running for the fact that it’s more energetically demanding and has a greater fitness element due to having to overcome gravity. Downhill running for the fact that it causes considerably more muscle damage due to the eccentric actions of the muscle when resisting gravity. You can train these two systems separately to build a more complete trail skillset.
How to Train for Better Downhill Running
The most important aspect to train, evident by the studies above, seems to be to manage the decline in performance on downhill sections. Downhill running seems to be a weakness in slower finishers as these are the sections they slow down in the most when compared to faster finishers. This happens due to various factors, probably most evidently due to muscle breakdown because of the eccentric nature of downhill running, which causes muscle pain. The eccentric portion of a movement is where the muscle lengthens under tension, i.e. when your thigh muscle acts like a brake to slow you down while descending.
The plan is simple: train your eccentric muscle strength so you can adapt to this stimulus and not bomb out on the descents.
On the trails:
- Run repeats on a steep hill (12–15% gradient), focusing on controlled descents without walk breaks.
- Increase overall elevation gain in general, what goes up must come down.
- Include technical downhills to build agility and strengthen the smaller stabilising muscles.
- Don’t overdo it and recover well. It can take up to three days to bounce back from a hard eccentric session.
In the gym:
- Focus on exercises like walking lunges, reverse lunges, box step ups and downs, quad extensions (focus on the downward portion), eccentric focused squats, or Bulgarian split squats.
- Perform all exercises within the muscular endurance range of 15-20 repetitions, with less than 60 seconds of rest between sets and exercises.
- Work on prehab exercises like tibialis raises, eccentric calf raises, or band assisted ankle adduction and abduction.
- Overload with plyometrics such as squat jumps, lunge jumps or Bulgarian split squat jumps.
Why Variable Pacing Beats Steady Effort on Trails
A variable pacing strategy simply means conserving energy on the climbs and making up time on the downhills. Logically you can only climb as fast as your lungs and legs will allow you to, the downside is an enormous metabolic cost that does not outweigh the benefits. The amount of time you can save on the downhills is exponentially more as a slower runner. This has far less consequence on the body as climbing faster will have. This is why elite runners have a more varied pacing strategy, they conserve on the uphills, but more importantly they capitalise on the downhills.
On the trails:
In your training runs run your uphill sections at a slower pace than you think you can and try and run your downhill sections at a faster pace than you are used to. Practicing this in training will ingrain variable pacing into your race day strategy. The goal is to reduce the cost of running on the uphill while reducing time loss on the downhill sections.
Don’t Get Swept Up At the Start
This is quite difficult for newer runners, the music, the nerves, the vibe, its captivating and you don’t want to be left behind. However, as the literature suggests, faster finishers actually start the race at a slower relative pace than slower finishers. This means that faster finishers pace themselves to run slower than they theoretically can at the start of a race, probably due to improved ‘teleoanticipation’- the brain’s built-in pacing mechanism that helps manage effort relative to the known endpoint of exercise (Ulmer, 1996). Slower finishers on the other hand run faster and harder than they theoretically can, which seems counter intuitive as they typically lack the fitness to keep on running at high intensities. Whereas faster finishers are conditioned to do just that. So, stick to your plan. Start a little easier than you think you should, you’ll catch the over-eager runners later.
Putting It All Together: Train Smart, Race Smarter
Improving your uphill running ability requires long periods of training as it is purely a fitness element. With the fitness you have now you can vastly improve your finish times by working on downhill running, it all comes down to technical ability, self-confidence, and muscular adaptations, which take a relatively short amount of time to improve. Pick the low hanging fruit: improving your downhill capability, which will ultimately save you the most time on race day. Uphill fitness is a result of months or years of accumulated fitness, this will come eventually with consistent training. Furthermore, a variable pacing strategy improves efficiency and subsequently race time.
FAQs
Q1: What is the best pacing strategy for ultra trail running?
The best pacing strategy for ultra trail races is variable pacing—conserving energy on climbs and running faster, controlled descents. Research shows elite runners slow down less on downhills, gaining a significant overall advantage.
Q2: Why do downhill sections matter so much in ultra trail races?
Downhill sections are where most runners lose time due to muscle fatigue from eccentric contractions. Training for downhill running improves muscle resilience, reduces potential fatigue, and can dramatically improve finish times.
Q3: How can I train for downhill running?
Include steep downhill repeats, technical descents, and eccentric-focused gym work like lunges, squats, and plyometrics. Recover well, as eccentric sessions take longer to bounce back from.
Q4: Should I start an ultra trail race fast or slow?
Start slower than you think. Research shows faster finishers pace themselves conservatively early on, leveraging a more gradual decline in pace across the race and avoiding early burnout.
Q5: What’s the difference between trail and road running pacing?
Unlike road running, where consistent pacing yields better results, trail running rewards variable pacing. The best trail runners adjust effort to terrain—slowing on climbs, speeding up on descents—to maintain efficient oxygen use.
References
CORBí-SANTAMARíA, P., HERRERO-MOLLEDA, A., GARCíA-LóPEZ, J., BOULLOSA, D. & GARCíA-TORMO, V. 2023. Variable Pacing Is Associated with Performance during the OCC® Ultra-Trail du Mont-Blanc® (2017–2021). International journal of environmental research and public health, 20, 3297.
DE WAAL, S. J., JACOBS, S. D. & LAMBERTS, R. P. 2025. Pacing analysis and comparison of TOP-10 and NOT TOP-10 Ultra Trail Cape Town 100-km finishers. Journal of sports medicine and physical fitness, 65, 218-224.
GENITRINI, M., FRITZ, J., ZIMMERMANN, G. & SCHWAMEDER, H. 2022. Downhill Sections Are Crucial for Performance in Trail Running Ultramarathons—A Pacing Strategy Analysis. Journal of functional morphology and kinesiology, 7, 103.
ULMER, H. V. 1996. Concept of an extracellular regulation of muscular metabolic rate during heavy exercise in humans by psychophysiological feedback. Experientia, 52, 416-420.