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Transitioning From a Marathon to a 50K

The expert coaches at CTS breakdown the differences between running a marathon and a 50K to help you transition from 26.2 to 31.1 on the trails smoothly.

UltraSignup News

May 31st, 2024

8 min read


As many marathon runners make the leap to ultramarathon distances, the most important thing to understand is that an ultramarathon is not simply a longer marathon. Yes, 50 kilometers is 31.1 miles, just 4.9 miles longer than a marathon. But the challenges, terrain, running surface, and duration of a 50K are significantly different. Marathon runners preparing for their first 50K should address these differences in their training.

Road Marathons vs. Trail Ultramarathons 

Road marathons and trail ultras have very different characteristics. Compared to trail ultras, even “hilly” road marathons are remarkably flat. Here are just a few more differences: 

Keep etiquette in mind, too. Dropping cups and wrappers may be acceptable in road marathons, but trail races operate with a “leave no trace” mentality, so pack out your food wrappers! 

⏱️ Marathon vs. 50K Pacing 

The pace for a trail 50K is slower than a competitive marathon pace and heavily influenced by elevation, ascent/descent, trail surface, and significant temperature swings. Instead of a minutes-per-mile pace target, the best approach for a trail 50K is to pace based on Rate of Perceived Exertion (RPE). Running through a rock garden is slower than running on a nicely groomed gravel road, even when the effort level is the same. Regardless of the conditions, with RPE you can stay within your physiological capacities for a given duration. 

🏔️ Terrain/Environment/Elevation 

The course for a trail 50K may include dirt roads, pavement, and single track trails, and runners may encounter water crossings or multiple microclimates depending on the change in altitude. Athletes must prepare for the terrain and environmental challenges specific to goal events. This may mean learning to run with poles, a hydration vest, and extra clothing.  

🌮 Marathon vs. 50K Nutrition 

Completing a trail 50K can take 1.5 times to twice as long as completing a road marathon, which changes your fueling strategy. The pace and intensity are generally lower than a competitive marathon, which means the trend of maximizing carbohydrate intake (i.e., 90-100 grams of carbohydrate per hour) may not be necessary. However, you still must be able to consume a steady stream of food and fluid for five to ten hours without suffering gastric distress.  

💦 Hydration for 50K vs. Marathon 

Runners who finish marathons in 3-4.5 hours can get away with moderate dehydration without terrible consequences. That’s not the case for 50K trail races that can take well over five hours. Athletes must learn to align fluid intake with intensity level, nutrition strategy, and the environmental conditions (heat, humidity). In marathons, there are typically water stations every mile. In trail 50K races, runners frequently carry fluid because aid stations are irregularly spaced and can be far apart. Keep etiquette in mind, too. Dropping cups and wrappers may be acceptable in road marathons, but trail races operate with a “leave no trace” mentality, so pack out your food wrappers! 

🗺️ Navigation 

On most trail courses, the turns are well marked but it’s not uncommon for trail runners to take wrong turns and turn 50Ks into 55Ks. Similarly, courses aren’t always exactly the advertised distance. While this isn’t acceptable in road marathoning, it’s just part of ultrarunning culture. Be familiar with the course ahead of time, noting especially the locations of aid stations and major climbs and descents. Better yet, load the course onto a GPS watch or handheld device. Be cautious about using phones for race navigation, as battery life and cell reception can be problematic. 

👟 Shoes for Marathon vs. Trail 50K 

Don’t wear lightweight, carbon-plated “super shoes” for a trail 50K. They work for road marathons because improving running economy (the energy cost of running) is critical component for going faster. Trail and ultrarunners sacrifice running economy for the sake of reducing muscle damage and increasing stability, and improving comfort (Koop 2023). Prime examples include using trail shoes (as well as running vests and trekking poles).  

Training to Transition From a Marathon to a 50K 

⚡️ Train All Intensity Zones! 

Race pace for a 50K is slower than marathon pace, and there may be long stretches of hiking. That doesn’t mean 50K training should be all low-intensity workouts. Sensible training for a 50K incorporates the full spectrum of intensities. This is because maximizing fitness (including maximum aerobic capacity or VO2 max) makes your “all day pace” faster. You’re less likely to battle time cuts and you’ll have more wherewithal to cope with adversity. 

Training for a 50K should focus on the least race-specific aspects of fitness first and then gradually become more race specific. If you have six months to prepare, you could spend the first period working on VO2 max intervals. Then you might transition to blocks of lactate threshold workouts. In the final month, spend more time at a moderate endurance pace, but with more climbing and descending and long runs and hikes. 

⌚️ Train by Time, Not Distance 

Time-at-intensity matters more than distance traveled. When you consider climbs and descents, rough surfaces, and technical terrain, ten miles in the mountains can take twice as long as ten miles on a flat track. A mile does not always equal a mile, but an hour equals an hour. The same goes for workouts. Instead of mile repeats, you might do eight-minute intervals on trails. 

📉 Train for the Climbs and Descents 

A little downhill-specific training goes a long way. Too much causes excessive muscle damage that requires long recovery periods, which displaces productive training in that timeframe. Instead, take the total elevation change of your goal event, say 6,000 vertical feet, and aim to get a total of 6,000 feet of elevation change over the course of your training week.  And skip the weighted vests. Carrying up to about five percent of your bodyweight in a hydration vest is event specific. Adding more than ten percent of your bodyweight is not beneficial because it changes your running kinematics (Cartón-Llorente 2023). 

🥪 Train Your Gut 

The amount of food and fluid your gut can take in and process is trainable, as is your ability to consume calories continually over several hours. For a 50K you’ll want to prioritize carbohydrate but also consume some fat and protein. A good starting point is 200-250 calories per hour, mostly from carbohydrates and in small portions. Carbohydrates are four Calories per gram, so 200-250 Calories would approximately 50-60 grams/hour of just carbohydrate. If eating mixed macronutrient foods, this may net more like 35-50 grams of carbohydrate. If you choose to increase carbohydrate intake, increase to maybe 70 g/hr in training to see how you tolerate it. Find foods that work for you (i.e., provide energy, don’t cause gastrointestinal distress) and that you’ll actually eat after running for majority of your day as tastes, cravings, and tolerances for foods change. 

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Cartón-Llorente, Antonio et al. “Training Specificity in Trail Running: A Single-Arm Trial on the Influence of Weighted Vest on Power and Kinematics in Trained Trail Runners.” Sensors (Basel, Switzerland) vol. 23,14 6411. 14 Jul. 2023, doi:10.3390/s23146411 

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