How to Train for a 50 Mile Race

For most runners it is 16 to 24 weeks, and where you land in that window comes down to where you are starting from. The honest floor is about 16 weeks, and that only works if you have already finished a 50K or a marathon and you are holding a 35 to 40 mile per week base. If you are marathon fit but have never run an ultra, give yourself 20 to 24 weeks. If you run 15 to 25 miles a week, plan on 24 to 28. And if you are brand new to the ultra distance, build a base first and budget 28 weeks or more. A 50 miler is a real step up from the 50K. The extra weeks are not there so you can pile on more hard work, they are there so you can grow your volume and a back-to-back block slowly, without breaking yourself in the process.

Most runners peak somewhere between 40 and 70 miles per week for a 50 miler, and you can finish just fine on the low end if your long runs and your consistency are there. A lot of solid finishers peak around 50 to 60 miles a week, which is the common sweet spot in published plans. But more is not automatically better. iRunFar warns that past roughly 60 to 70 miles per week, or 8 to 10 hours of running, most amateur runners are walking a fine line between getting fitter and getting hurt. On hilly trail, count your week by time (think 6 to 10 hours) instead of chasing a mileage number, because the vert makes those miles way harder than they look on the flat.

There is no magic number here, and you do not need to run the full 50 miles in training. Most plans build the single longest run up to about 26 to 32 miles, or roughly 4 to 5 hours on your feet, done a few weeks out from race day. Jason Koop of CTS has coached successful ultrarunners whose longest run was as little as 20 percent and as much as 80 percent of race distance, and his point is that the one longest run matters way less than your total weekly volume and your back-to-backs. A good floor is a 4 hour long run, just so you can run through a full fueling cycle and see what your stomach does. On hilly courses, go by time, not distance. Time on feet is the thing your body is actually adapting to.

For a 50 miler the back-to-back long run is the single most valuable session you can do, and most coaches build the whole plan around it. You run long on Saturday, then go out and run another, shorter long run on Sunday on tired legs. That teaches your legs to keep moving while they are already cooked and your gut to keep taking fuel late in a long day, which is exactly what a 50 throws at you, but at a fraction of the injury risk of one giant 35 mile day. A common target is 35 to 50 total miles across the two days, with the second day often given to you by time instead of distance. A lot of runners do two or three back-to-back blocks roughly seven, five, and three weeks out, then taper. They are optional if you just want to finish. But they make race day go a whole lot better.

I would strongly recommend it, though it is not strictly required. A 50K is the natural stepping stone to a 50 miler. It teaches you aid stations, trail fueling, power-hiking, night gear if your race has any, and the plain feeling of moving for hours, all at lower risk than jumping straight to 50. A lot of runners use a 50K as a hard training day or a tune-up race about 4 to 6 weeks before their 50, which doubles as a long run and a full dress rehearsal of your pacing and fueling. If you have never run an ultra at all, do a 50K first, then build to the 50. If you are already an experienced trail runner with a strong base, you can train straight for the 50, but slot a long supported effort in somewhere as your rehearsal.

A typical peak week is about five days of running. You get two or three easy runs of 5 to 8 miles, one quality day of hill repeats or a rolling tempo, a weekend long run of 18 to 26 miles on race-like terrain, and on peak weeks a back-to-back easy long run of 8 to 14 miles the next morning on tired legs. One or two days are full rest or easy cross-training, plus one or two short strength sessions for the legs, hips, and core. Keep about 80 percent of your running genuinely easy, the kind where you can hold a conversation, and save the hard breathing for one or two focused days. The long run and the back-to-back are the anchors. Everything else is just there to let you repeat them, healthy, week after week.

Taper over the final 2 to 3 weeks. After your last big back-to-back block, which usually lands about 3 to 4 weeks out, cut your weekly volume by roughly 20 to 30 percent each week while keeping a little intensity, just a few short efforts, so your legs stay sharp instead of going flat. Keep your last long run short, around 90 minutes to 2 hours about 10 days out. In this window the goal is to shed the fatigue you have been piling up, not add to it. The taper feels strange, and the phantom aches and the restlessness are normal, not a sign you are losing fitness. You cannot gain fitness in the final two weeks. But you can absolutely waste it by training through them.

Aim for roughly 60 to 90 grams of carbohydrate per hour, which is about 240 to 360 calories, and start fueling within the first 30 minutes, taking something every 20 to 40 minutes. A glucose-plus-fructose mix lets your gut absorb more than a single sugar can, and rotating in real food mid-race (bars, fruit, savory aid-station food) helps over a day-long effort. For sodium, a common starting band is 500 to 700 milligrams per hour in temperate conditions and 800 to 1200 milligrams per hour in heat, with fluid taken to thirst, adjusted for how salty and heavy a sweater you are. The non-negotiable is to train your gut to these numbers on long runs and back-to-backs, never experiment on race day. Our free ultra fueling calculator turns these ranges into an hour-by-hour plan for your weight, goal time, and expected heat.