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Running · 16 weeks16-week 50 km ultra training plan
A 16-week 50 km ultra training plan takes a runner on 55 km a week with a 4:00 marathon behind them from where they are to race day in 17 weeks, building to 90 km in the biggest week. It spends 6 weeks in base, 6 weeks in build, 2 weeks in peak, 2 weeks in taper, with 3 lighter weeks to absorb the work, on 6 days a week. That is 4 weeks shorter than we would choose — see below for what that changes.
Build my 50 km ultra plan — freeBuilt from your own numbers and your own week. The first week is free.
16 weeks is not enough to add meaningful aerobic fitness for a marathon. What it can do is keep you healthy, sharpen what you already have and get the pacing right. If you are starting from a solid base of long runs, you can finish well; if you are not, the kindest thing this plan can tell you is to pick a later race or a shorter distance.
What the weeks are for
| Base | 6 weeks — aerobic volume, mostly easy, the foundation everything else stands on |
|---|---|
| Build | 6 weeks — the harder sessions arrive and volume keeps climbing |
| Peak | 2 weeks — the biggest, most race-specific weeks |
| Taper | 2 weeks — volume drops, intensity stays, you arrive fresh |
| Lighter weeks | 3, roughly every fourth week |
| Total | 1168 km, 150 hours |
The 17 weeks
Generated for a runner on 55 km a week with a 4:00 marathon behind them.
| Week | Phase | Volume | Load | |
|---|---|---|---|---|
| 1 | Base | 55 km | 312 | |
| 2 | Base | 60 km | 337 | |
| 3 | Base | 64 km | 358 | |
| 4 | Base · down | 44 km | 252 | |
| 5 | Base | 69 km | 384 | |
| 6 | Base | 73 km | 409 | |
| 7 | Build | 73 km | 436 | |
| 8 | Build · down | 53 km | 309 | |
| 9 | Build | 78 km | 461 | |
| 10 | Build | 82 km | 485 | |
| 11 | Build | 87 km | 506 | |
| 12 | Build · down | 62 km | 366 | |
| 13 | Peak | 89 km | 513 | |
| 14 | Peak | 90 km | 521 | |
| 15 | Taper | 77 km | 435 | |
| 16 | Taper | 60 km | 347 | |
| 17 | Race · race | 55 km | 482 |
The biggest week, session by session
Week 14, peak phase — the heaviest week of the block.
| Monday | Easy run — 1h12, 10.4 km |
|---|---|
| Tuesday | Threshold — 2 × 10 min — 0h54, 8 km |
| Tuesday | Strength — lower body — 0h27 |
| Wednesday | Easy run — 1h12, 10.4 km |
| Friday | Race pace — 9 km — 1h13, 11.4 km |
| Saturday | Easy run — 1h27, 12.7 km |
| Sunday | Long run with a fast finish — 3h59, 37.2 km |
The paces
| Pace band | Per kilometre |
|---|---|
| Easy — the ceiling, not the target | 6:23 |
| Marathon pace | 5:44 |
| Threshold | 5:25 |
| Interval (VO₂max) | 4:54 |
Computed from VDOT 37.9, derived from that time trial using Jack Daniels' model. Your own numbers will differ — the plan builds these from a time trial you enter.
What this plan says out loud
Some sessions have been cut to fit the time you said you have — 75 minutes on a weekday and 240 at the weekend. That is a real constraint and the plan respects it, but be aware the long session is the one that matters most: if you can find more time anywhere, find it on the weekend.
On 6 days a week there is nowhere to put 40 km without prescribing runs nobody should be doing. The plan caps individual easy runs at 14 km and carries less volume than your target as a result. More days would do more for you than longer runs.
Race day looks like about 4:45:29 on today's fitness — Run 4h 45. Assumes a flat course, reasonable conditions and a sensible first half.
Common questions
Is 16 weeks enough for a 50 km ultra?
Only if you already train regularly. What it can do is keep you healthy, sharpen what you already have and get the pacing right.
How many days a week does it train?
6, on Monday, Tuesday, Wednesday, Friday, Saturday, Sunday in this example. You tell the plan which days you actually have, and it never puts two hard days back to back.
What is the longest session?
Long run with a fast finish, about 3h59 and 37 km. It is capped by share of the week, by absolute length, and by the time you say you have.
Can I use this if I train at altitude?
Yes, and you should say so when you build it. Paces and power are corrected for the difference between where you tested and where you train — in Johannesburg that is roughly 8%, or about 26 seconds a kilometre on an easy run for a 20-minute 5 km runner.