If you can run a marathon, you can finish a 50K. The extra five miles are not the hard part. The hard part is that trail ultras change the rules: pace stops meaning much, hills become a skill, fueling becomes a requirement, and the long run becomes about hours, not miles.
This plan is the one I would hand a marathoner who wants to finish a first trail 50K strong and healthy. It is built on time on feet, effort and durability. It is not built to win anything. That is on purpose. Most first-time ultrarunners need a finish, not a podium.
Are you ready to start a 50K plan?
This 16-week plan assumes you can already:
- Run 4 to 5 days a week without lingering pain
- Complete a 2-hour long run comfortably
- Run about 25 to 35 miles, or 4.5 to 6 hours, per week
If you are newer to running or brand new to trails, give yourself more runway. In my book I recommend an 18 to 22 week build for a first 50K for trail newcomers. Start with our 8-week trail running program for beginners, then come back here.
How to measure training on trails
On roads, miles and pace tell a clean story. On trails, they get messy. A 10-mile run with 2,000 feet of climbing is not the same as 10 flat miles. Track these four metrics instead:
- Time on feet: the most honest measure on trails.
- Effort (RPE): a simple 1 to 10 scale. Most of your running lives at 3 to 4 out of 10.
- Vert: elevation gain and loss. Climbing is load. Descending is load. They are different.
- Terrain: smooth dirt is not rocky singletrack. Adjust expectations.
Two rules keep this plan safe:
- Never increase the long run and total weekly load aggressively in the same week. Pick one.
- Every third or fourth week, cut the long run by 15 to 25% to absorb the work.
The weekly structure
- Monday: rest or mobility
- Tuesday: easy run, 45 to 60 minutes
- Wednesday: hills or power hiking session, 45 to 75 minutes
- Thursday: easy run plus 20 to 30 minutes of strength
- Friday: rest or short shakeout
- Saturday: long run (see table)
- Sunday: easy run, or the second day of a back-to-back weekend
Add strength training twice a week. Durability is what lets you stack weeks without getting hurt.
The 16-week first 50K training plan
| Week | Saturday long run | Sunday | Focus |
|---|---|---|---|
| 1 | 2:00 | Easy 0:45 | Trail time, easy effort |
| 2 | 2:15 | Easy 0:45 | Start fueling every 30 minutes |
| 3 | 2:30 | Easy 0:45 | Hike the steep climbs on purpose |
| 4 | 1:45 | Rest | Recovery week |
| 5 | 2:45 | Easy 1:00 | Add vert |
| 6 | 3:00 | Easy 1:00 | Practice race morning routine |
| 7 | 3:15 | 1:15 on tired legs | First back-to-back |
| 8 | 2:15 | Rest | Recovery week |
| 9 | 3:30 | Easy 1:00 | Race terrain if possible |
| 10 | 3:30 | 1:30 on tired legs | Back-to-back, test gear |
| 11 | 4:00 | Easy 1:00 | Full race fueling rehearsal |
| 12 | 2:30 | Rest | Recovery week |
| 13 | 4:30 | Easy 1:00 | Peak long run, race kit |
| 14 | 3:30 | 1:30 on tired legs | Final back-to-back |
| 15 | 2:00 | Easy 0:45 | Taper begins |
| 16 | Race | Celebrate | Race week: two short easy runs |
Times are hours and minutes at easy effort, hiking climbs as needed. If you feel beat up for more than 48 hours after a long run, repeat that week or cut the next long run back. The plan serves you, not the other way around.
Back-to-back long runs explained
A back-to-back is a long run followed by a medium run the next day. It teaches your body to run on tired legs without the injury risk of one giant run. Keep the second day easy. Its job is time on feet, not speed.
Train the climbs and descents
Use Wednesday for one of these:
- Hill repeats: 6 to 8 x 2 to 3 minutes uphill at a strong effort, easy back down.
- Power hiking repeats: 4 to 6 x 4 minutes on a steep grade.
- Rolling trail run: hilly route at easy effort, focusing on smooth descents.
Earn your downhills. Run gentle descents smoothly for weeks before you push steep technical ones.
Practice fueling on every long run
Fueling is the most common reason first 50Ks go sideways. Start by taking in carbohydrate every 20 to 30 minutes and build toward your race target. Set a timer. Early in long runs, people forget to eat until it is too late. Our full guide to what to eat during an ultramarathon covers how much and what.
Taper and race week
- Week 15: drop volume about 30 to 40%, keep a little intensity.
- Race week: two or three short easy runs, extra sleep, normal food with a little more carbohydrate the last two days.
- Lay out your kit two nights before. Nothing new on race day.
Race day: run the first half like a coward
Start slower than feels right. Hike every steep climb from the start. Eat early. Fix small problems while they are small. Read how to pace an ultramarathon before your race, and check the cutoffs. Most 50Ks are generous, but read our guide to ultra marathon cutoff times anyway.
For perspective: my 50K finishes over the years range from 5:41 to more than 10 hours, depending on the course, heat and how the day went. Finishing time on trails says more about the course than about you.
Related reading
- How to start ultrarunning: a beginner's guide
- Marathon to trail ultra
- Ultra running mental toughness
- How to prevent chafing on long trail runs
FAQ
How long does it take to train for a 50K?
About 16 weeks if you are already running marathons. 18 to 22 weeks if you are newer to running or trails.
How many miles a week do I need for a 50K?
Many first-timers finish well on 30 to 45 miles a week at peak. On trails, time on feet and vert matter more than miles.
Do I need to run 31 miles in training?
No. A peak long run of 4 to 4.5 hours plus back-to-back weekends prepares you without the injury risk.
About the author: Scott Millman, The Sloth, is a UESCA-certified ultrarunning coach and sports nutrition coach, co-founder of Sloth and Duck, and author of I Can Run A Marathon, Now What? He has spent 30 years on trails and in ultras, from 50Ks to 48-hour events, mostly in the middle and back of the pack.