Research · Guide ·
How to train for your first trail 50km
Your first 50km is a big step, but it's very achievable with a sensible plan. This guide covers how long to give yourself, what a training week looks like, and the three things that matter most on a hilly trail 50km: climbing, descending and fuelling.
Where are you starting from?
If you've run a marathon (or regularly run 2.5 hours or more), you can go straight into the 16-week plan below.
If your longest race is a half marathon, add an 8-week base phase first. Build up to:
- 4–5 hours of running a week
- A long run of about 2 hours, ideally on trails
- 2 strength sessions a week (more on this below)
Then start the 16-week plan. That's about 6 months in total, which is the right amount of time to let your legs, tendons and gut adapt.
A word on Granite Peaks
Our local race, the Granite Peaks 50K, is 52km with 4,000m of climbing and a 14-hour cut-off. That's a lot of climbing for a first ultra, and more than many trail 50kms.
It's a great goal if you already run in the hills. If you're new to trails or mountains, consider the Granite Peaks 25K (1,800m of climbing) as a first step, then the 50K the following year. Either way, train for the climbing, not just the distance.
Think in hours, not kilometres
On trails, the same 10km can take 50 minutes on a flat path or two hours over a mountain. So plan your training by time on feet, and keep most of it easy. You should be able to hold a conversation on easy runs.
The 16-week plan
This is an example, not a prescription. Adjust it to your week, your history and how you're recovering. Every fourth week is a lighter recovery week, which is when your body adapts to the training.
| Weeks | Weekly running | Long run | What to focus on |
|---|---|---|---|
| 1–3 | 4–6 hours | 2–2.5 hours | Easy running on trails, regular strength sessions |
| 4 | Recovery: about 3–4 hours | 1.5 hours | Rest and absorb the training |
| 5–7 | 5–7 hours | 2.5–3.5 hours | Add hill sessions and your first back-to-back weekend |
| 8 | Recovery: about 4 hours | 2 hours | Ease off |
| 9–11 | 6–8 hours | 3.5–4.5 hours | Back-to-backs, practise race fuelling and kit |
| 12 | Recovery: about 4–5 hours | 2–2.5 hours | Ease off |
| 13–14 | 7–9 hours | 4.5–5 hours | Peak weeks: long days on race-like terrain |
| 15 | About 4–5 hours | 2 hours | Taper: keep some short efforts, cut the volume |
| 16 | About 2–3 hours | Race day | Race week: short, easy runs and rest |
What a typical week looks like (weeks 9–11)
- Monday: rest
- Tuesday: easy run, 45–60 minutes, plus strength
- Wednesday: hill session, e.g. 6–10 × 2–3 minutes uphill at a hard but controlled effort
- Thursday: easy run, 45–60 minutes, plus strength
- Friday: rest or a short, easy run
- Saturday: long run, 3.5–4.5 hours on trails
- Sunday: second long run, 1.5–2 hours, easy
Back-to-back long runs
Instead of one enormous run, ultra runners often do two long runs on consecutive days, e.g. 4 hours on Saturday and 2 hours on Sunday. The second run starts on tired legs, which is what the second half of a 50km feels like, but with less recovery cost and injury risk than a single 6-hour run.
You don't need to run 50km in training. A peak long run of about 4.5–5 hours, plus a back-to-back, is enough for most first-timers.
Climbing: learn to power hike
On steep climbs, walking can be just as fast as running and costs less energy. In one study, above about 15 degrees, walking used less energy than running at the same climbing speed (Giovanelli et al. 2016).
- Practise power hiking on every long run: hands on thighs, short quick steps.
- Hike the steep sections early in the race, before you have to.
- If you'll use poles on race day, train with them.
Descending: train your quads
Downhill running causes more muscle damage than flat or uphill running, and on a mountain 50km it's often the descents that finish legs off. Build downhill running gradually in your long runs and hill sessions, so your legs are ready for repeated descents.
Strength training
Two short strength sessions a week make a real difference. In a 2024 review, heavy strength training improved running economy, and plyometrics (jumps and bounds) helped at slower speeds (read our summary). Focus on:
- Heavy, low-rep lifts: squats, deadlifts, step-ups, calf raises
- Plyometrics: skips, bounds, box jumps
- Single-leg work for balance on uneven ground
Learn good technique first, and keep strength sessions away from the day before your long run.
Fuelling: train your gut
Most first-ultra problems are stomach problems. The good news is that your gut can be trained: in one study, two weeks of practising carbohydrate intake while running cut gut symptoms by about 60% (read our summary).
- Start eating on runs over 90 minutes, from the first 30–45 minutes.
- Gradually work up towards 60–90g of carbohydrate an hour. That's a common target for long events, but build up to it.
- Use the same gels, bars or real food you'll use on race day.
- Drink to thirst. Drinking far more than you need can be dangerous (why over-drinking matters).
And eat enough day to day. Under-fuelling a big training block is a common cause of fatigue and injury (our REDs summary).
Race-day rehearsal
In weeks 9–14, use at least two long runs as dress rehearsals: race kit, race pack with mandatory kit, race-day breakfast and race fuelling. Nothing on race day should be new.
The short version
- Give yourself 16 weeks if you've run a marathon, or about 6 months from a half marathon.
- Keep most running easy, and plan by hours rather than kilometres.
- Build long runs to 4.5–5 hours, with back-to-backs.
- Practise power hiking, descending and fuelling on every long run.
- Strength train twice a week.
- Take the recovery weeks and the taper seriously.
This guide is general information, not individual advice. If you have an injury or a medical condition, speak to a physio or doctor before starting a new training plan.