How to Train for a 50k Ultra Marathon

Training for an ultramarathon is not the same as training for a marathon. While both events demand endurance, ultras bring new challenges: slower paces, extended time on feet, variable terrain, and often thousands of metres of climbing. On trails, you’re not only running longer, but also adapting to technical footing, steep gradients, and weather that can change drastically throughout the day.

With ultramarathons comes beautiful scenery.

That means preparing for a 50k goes far beyond simply adding mileage. Successful training needs to address:

• Mileage and volume – not just kilometres but total time on feet.

• Elevation – building strength for climbing and descending.

• Intensity – structured speedwork to improve efficiency.

• Nutrition and fuelling – practicing what and how you’ll eat during long runs.

• Gear and environment – managing temperature swings, hydration, packs, and shoes.

  
  

  

  And lots of uphill grunts!

  
  

At Wild Runner Coaching, I lean on both the science I learned in my UESCA Ultrarunning Coaching certification and the principles laid out by Jason Koop, one of the world’s leading ultrarunning coaches. His 3 principles are simple but incredibly effective when training for ultra and they are as follows:

1. Develop the physiology most specific to the event closest to race day, and the least specific furthest away.

2. At some point, incorporate three key workouts: Intervals, Tempo runs, and Steady state runs.

3. Work on weaknesses early in the season and sharpen strengths closer to the race.

Why Training for Ultras Needs Intensity

Race day might look like a long, steady grind — but training shouldn’t be only long, slow runs. Developing your VO₂ max and lactate threshold allows your easy paces to become faster and more efficient. Think of VO₂ max as your performance ceiling and lactate threshold as the point just before fatigue forces you to slow down. If your ceiling is too low, your lactate threshold can’t rise much either and therefore becomes your limiting factor. This intensity also helps you manage the inevitable uphill grunts that you will find sprinkled in different frequencies across ultra courses.

(The 3 phases below work on the assumption that you already have a good base running, fitness. If you are needing to develop base fitness and do not already have consistent running weekly mileage then this should be done before you begin phase 1.)

Phase 1: VO₂ Max Training

VO₂ max intervals are very intense but deliver huge benefits. These sessions, known as intervals, typically involve 1–6 minute efforts at a pace you can sustain for that duration, followed by equal recovery. For example: 5 × 3 minutes RPE 10 (rate of perceived effort, see image below) with 3 minutes jog recovery.

• Flat intervals build raw speed but create more impact stress.

• Hill intervals are often better for trail runners: they drive your heart rate up, build strength, but reduce pounding and therefore impact stress is less.

  
  

Because VO₂ sessions are so taxing, they should be used sparingly — usually in short training blocks of a few weeks (2-4 weeks) and only included in one to two runs per week. The goal is to raise the ceiling, not to live at it.

Phase 2: Lactate Threshold Training (Tempo Runs)

Once VO₂ work has lifted your ceiling, it’s time to push your lactate threshold higher. Your lactate threshold pace is roughly the maximum pace that you can hold for 1 hour, although varies quite considerably between trained and untrained athletes. This is done using tempo runs consisting of sustained efforts of 8–20 minutes at a RPE of 8–9.

Recovery between segments is half the effort time (e.g., 10 minutes on / 5 minutes recovery).

The critical detail: every tempo effort within a workout should be at the same pace. If your later reps fade significantly, you’ve gone too hard or have done enough and should stop.

Physiologically, tempo training:

• Expands mitochondrial size and density (think of mitochondria as your “energy plants” that produce the energy your muscles require).

• Improves the body’s ability to clear and reuse lactate.

• Teaches the mind and body to stay relaxed under controlled discomfort.

Phase 3: Endurance & Steady State Runs

For approximately 8-12 weeks, leading up to race day, training shifts toward endurance and race specificity. Steady state runs, completed at an RPE of 7, slot into endurance runs, as extended segments (15–60 minutes) at a pace above endurance but below threshold/tempo efforts. During a 50k you will bounce between endurance pace and steady state pace, making this one of the most specific workouts for race preparation.

These runs train the body to manage lactate just under the tipping point, improving your ability to run long at a steady effort without fading.

This shows what these runs should feel like according to the RPE (Rate of Perceived Effort) scale and run types referenced above. Due to the changeable terrain of trails its more effective to work using RPE rather than a specific pace or heart rate.

The Role of Recovery (super-duper easy paced) Runs

Ultramarathon training carries high frequency and workload demands. To balance the stress of intervals, tempos, steady state, and long runs, recovery runs are essential. These should feel substantially easier than endurance pace — think “conversational jogging.”

Even though they’re easy, recovery runs:

• Increase weekly volume without adding too much extra stress.

• Build durability in tendons, ligaments, and bones.

• Aid blood flow and muscle repair.

Skipping recovery runs often leads to burnout or injury; including them allows you to handle the workload required for ultra preparation.

The role of the Long Run

The long run is a cornerstone of ultramarathon training, but there’s no single “magic distance” that guarantees success. Instead, think of it as your weekly opportunity to practice the demands of race day — time on trails, terrain-specific effort, nutrition and hydration strategies, and even problem-solving for the inevitable challenges like weather shifts, boredom, or (for some athletes) managing menstruation and even toileting.

A long run should include a natural mix of running and power hiking, depending on the terrain. Build these runs gradually and consistently, but avoid making them so long that recovery spills over into the following days. The goal is balance: long enough to build endurance and resilience, but not so long that it undermines the rest of your training week. For most athletes, working up to 3–4 hours is a sweet spot — plenty of time to practice, adapt, and grow your confidence without overloading your system.

How Much Training Do You Really Need?

The classic question: How many kilometres do I need to run per week to train for a 50k?

The answer: it depends. A podium chaser’s training looks very different from a first-time finisher’s. Many runners on the start line are there to complete rather than compete — they’re balancing training with jobs, families, and everyday life and are out there for the challenge and experience that race day offers. They don't have endless hours and so their training needs to be smart and efficient.

Because trail running pace varies so much thanks to the terrain variability, training volume is better measured in time, not distance. As a rough benchmark, being able to build up and handle around 6 hours of running per week, sustained for at least 3 consecutive weeks close to race day, is often enough to finish a 50k. That’s far less than many people expect — but it's important to remember that it has to be the right 6 hours, with quality and specificity built in.

As you'd expect, not every race is the same and course profiles and personal goals matter. A 50k with 2500m of climbing may take several hours longer than one with 1000m, or if you have a specific goal time in mind you will need to train harder/longer, so preparation and training should reflect the demands of your race and personal goals.

Building Durability: The Hidden Challenge

Your cardiovascular system adapts quickly. With a few months of training, your aerobic fitness may feel “ultra-ready.” But the limiting factor in ultras is rarely your lungs or heart — it’s your musculoskeletal system.

Muscles, tendons, ligaments, and bones adapt much more slowly. Building the resilience to handle 6–10 hours of running stress on race day requires time and consistency. Ramping too quickly often leads to injury.

If you’re running low mileage now, start building gradually. Even if your race is many months away, the earlier you begin, the better. There’s no shortcut to musculoskeletal durability: it comes only from patient, progressive stress over time. Significant gains in this area happen year on year as opposed to month on month, so be patient. 

Specificity

Most importantly, train for your race including the terrain, the climbs, and the conditions you’re likely to face. Early in your training, identify and put extra time into your weaknesses. If steep descents are your nemesis, start practicing them early in your training blocks. Then, as the event gets closer, shift toward the specific demands of your course: maybe that’s heat training, altitude work, steep uphill work, or long runs on rocky trails. If you can’t access the actual trails you will be racing on, that is OK and the case for many people who travel long distances for their chosen races, just replicate what you can, as closely as you can, so that you have controlled as many of the controllables for race day as possible. 

Nutrition

Lastly, there’s nutrition, and this could be a whole blog post on its own (watch this space). The mistake I see most often, including from myself in my early days of running ultra, is leaving this until race day. Your gut needs training just like your legs do. Use your weekly long runs to test different foods, gels, and hydration strategies until you know what works and when. That way, nothing on race day comes as a surprise. 

Gastrointestinal issues including nausea, diarrhoea, bloating, and cramps are one of the most common reasons for people to DNF in ultramarathons, so do not underestimate the importance of this step. It can quite literally make or break your race day. 

Key Takeaways

Training for a 50k is about more than running long. To prepare well, you need:

• Early blocks of VO₂ max and lactate threshold work.

• A shift toward steady state and endurance-specific work as race day nears.

• Plenty of recovery runs to absorb training load.

• Long-term, gradual progression to build musculoskeletal durability.

• Consistency is key. Work at a level that is challenging enough to create fitness and strength but not so hard that you create injury or burnout forcing you to stop.

• Add in specifics relating to your event in the 8-10 weeks leading up to race day

• Practice your nutrition and hydration well in advance so you train your gut to absorb the nutrients you need efficiently.

  
  

This is what defying the odds looks like. The doubt and worry is gone and a seat for some very tired legs is not far away. Good, consistent training will build the skills needed to achieve the goals you set.

Enjoy the journey

For many runners, the real win isn’t the finish time — it’s arriving at the start line healthy, confident, uninjured, and ready. With purposeful, specific training, you give yourself the best chance not only to complete your 50k, but to truly enjoy it.

My hope for every ultrarunner is that they find joy in the journey. We spend far more hours training than we do racing, so those miles should feel like soul food, not just homework. Mix it up, explore new trails, join a group run, or share the miles with a friend. A good plan should challenge you, and it should also keep training interesting enough to avoid burnout.

The journey to the start line is where the magic happens. The race itself? That’s just the bonus.

"Ultras aren’t just races. they’re the stories you write, one training run at a time — and at Wild Runner Coaching, I help you make every kilometre count.”