Climbing, and when to stop running
Above a certain gradient, walking is simply cheaper than running.
The energy cost of going uphill has been measured across a wide range of slopes, walking and running. The two curves cross 1. Past that crossing point, running a climb costs more than walking it for the same progress.
This is one of the few places in trail running where the science gives a clear instruction. It is also the one that runs against instinct. Experienced trail runners walk the steep bits. Beginners lose the race trying not to.
Poles change the maths on steep ground: in the conditions studied, they lowered the cost of uphill walking 2. Whether they help you depends on the profile, the rules, and whether you have actually trained with them.
Descending decides the second half
Running downhill damages muscle in a way flat running does not.
Your muscles lengthen under load, and that causes real structural damage. The problem is not that the descent hurts. It is that everything after the descent costs you more 3.
This has been measured over a real mountain ultra: after the race, running economy and mechanics were changed in ways that fit accumulated damage 4.
So descending has to be trained, and trained gradually, because it is the stress that leaves you sore for days. How steep, how often, how fast to build up — none of that has been tested. We say so rather than inventing a protocol.
The formats, 20 to 100 km
| Format | What it really is | What decides it |
|---|---|---|
| 20–30 km | Two to four hours, often with a lot of climbing | Holding a climbing effort, and still being able to run the flats late |
| 40–55 km | Four to eight hours | Surviving the descents, and a food plan that holds up |
| 70–100 km | Ten hours to a full day and night | Time on your feet, self-sufficiency, digestion, and thinking straight when tired |
Preparation lengths here are conventions too: twelve to twenty-four weeks depending on the format and where you start. No trial sits behind those numbers, and we would rather label them than dress them up.
Eating and drinking on a trail
Lower intensity, much longer day. Your stomach is usually happier and your plan matters more.
Be aware that the published advice openly disagrees with itself. The paper written specifically for ultras says 30 to 50 g of carbs per hour 5. General endurance reviews say a lot more 6. Nobody has settled it, and a single confident number should make you suspicious.
Weighing yourself is a poorer guide here than on the road. Over very long events, body weight does not track hydration reliably 7.
Where the research goes quiet
We would rather tell you than fill the space.
On trail specifically there is no usable published evidence on: how much of a race runners actually walk, how technical ground changes intensity, what altitude does to a non-acclimatised runner, how long recovery takes by format, or how to taper for an ultra.
Anyone giving you numbers on those is extrapolating. That includes us. The difference is we tell you which parts are extrapolation.
Questions people actually ask
Should I walk the climbs?
How do I train descents if I live somewhere flat?
How do I compare a trail race to a road distance?
Do I need poles?
References
Every figure above rests on one of these studies. Author and year are enough to find the paper.
- Minetti (2002)
- Giovanelli (2019)
- Vernillo (2017)
- Vernillo (2015)
- Tiller (2019)
- Burke (2019)
- Hoffman (2018)
