Ultra running is any footrace longer than a standard marathon, meaning anything beyond 26.2 miles (42.195 km). The most common distances are 50K (31 miles), 50 miles, 100K (62 miles), and 100 miles, though races extend far beyond that, with the longest certified race distance reaching 3,100 miles. What sets ultra running apart from road marathons isn’t just the extra mileage. Most ultras take place on trails, through mountains, deserts, or wilderness, and they demand a fundamentally different approach to pacing, nutrition, and mental resilience.
Common Race Formats
Ultra races generally fall into two categories: fixed-distance events and timed events. In a fixed-distance race, you run a set course (50K, 100 miles, etc.) and the clock stops when you cross the finish line. In a timed event, you run as far as you can within a set window, typically 12 or 24 hours, often on a looped course. Both formats attract different kinds of runners. Fixed-distance mountain races reward technical skill and climbing ability, while timed events on flat loops favor pure endurance and consistent pacing.
There are also multi-day stage races, where runners cover a long route broken into daily segments. These range from week-long desert crossings like the Gobi March (a seven-day journey across the Gobi Desert) to extreme endeavors like the Trans-Europe race, which covered roughly 5,100 kilometers from Lisbon to Moscow. In stage races, managing sleep, nutrition, and recovery between segments becomes as important as the running itself.
What Ultra Running Does to the Body
The physical toll of ultra running goes well beyond typical marathon fatigue. Muscle damage is significant: a marker called creatine kinase, which indicates muscle breakdown, can spike to 100,000 to 200,000 units per liter after an ultra, depending on fitness level and race length. For context, normal resting levels are under 200. That degree of muscle damage means your body is essentially breaking itself down and rebuilding during the race.
Digestive problems are one of the most common issues ultrarunners face. Gastrointestinal bleeding after an ultra is not uncommon, and nausea, vomiting, and an inability to keep food down can derail even well-trained runners mid-race. The heart also shows measurable changes during and after ultras, with shifts in cardiac biomarkers and heart function that typically resolve within days or weeks of finishing.
Despite all this, the sport attracts a surprisingly broad age range. The average ultramarathon finisher is in their mid-40s. Data from over 210,000 runners in timed ultra events spanning more than a century shows the mean age hovering around 45 to 46 years. This isn’t a young person’s sport in the way sprinting or even road marathons tend to be. Endurance, patience, and experience can offset the decline in raw speed that comes with age.
How Runners Train for Ultras
Ultra training looks different from marathon training. The cornerstone technique is back-to-back long runs: running high mileage on consecutive days to teach your body to perform on tired legs. This simulates what happens deep into a race when you’ve been moving for 10, 20, or 30 hours. A common approach is to schedule these double-day efforts at key points in a training cycle, typically around seven, five, and three weeks before race day.
The volume scales with race distance. For a 50K, runners typically aim for 30 to 40 miles spread across two consecutive days. For a 50-miler, that increases to 35 to 50 miles over two days. For a 100-miler, the target is 40 to 55 miles over two days. These aren’t easy jogs. Some runners use the first day for speed-focused efforts and the second day for climbing, building both fitness dimensions simultaneously. Most recreational ultrarunners benefit from doing back-to-back long runs at least twice before their goal race.
Fueling During a Race
Nutrition is one of the biggest differences between a marathon and an ultra. In a marathon, you can get by on gels and water. In an ultra lasting 10 to 30 hours, you need real food, and lots of it. The recommended intake during racing is 150 to 400 calories per hour, with 30 to 50 grams of carbohydrates and 5 to 10 grams of protein per hour. Longer races push toward the higher end of that range because the caloric deficit compounds over time and becomes harder to tolerate.
Hydration targets are roughly 450 to 750 milliliters of fluid per hour, or about 150 to 250 milliliters every 20 minutes. But fluid alone isn’t enough. Sodium loss through sweat can lead to dangerously low blood sodium levels, a condition called hyponatremia. Runners need sodium concentrations of 500 to 700 milligrams per liter of fluid, which is higher than what most commercial sports drinks provide. Many ultrarunners carry salt capsules or add electrolyte tablets to their water to bridge this gap.
In practice, ultrarunners eat a wide variety of calorie-dense foods during races: sandwiches, potatoes with salt, nut butters, broth, candy, and whatever else their stomach will accept. Finding foods you can tolerate after 15 hours of running is a skill that takes practice, and most runners experiment extensively during training.
Essential Gear
Most trail ultras require runners to carry specific gear, and even races without mandatory lists benefit from smart preparation. A hydration vest is the foundation, allowing you to carry water bottles or a bladder along with pockets for food, a phone, and emergency supplies. For races that extend into darkness, headlamps (often two, for backup) are essential.
Safety gear matters more in ultras than in shorter races because you’re often hours from the nearest road. An emergency blanket weighs just a few ounces and can be lifesaving if you’re injured and need to stay warm while waiting for help. A small first aid and blister kit, a lighter for emergency fire or sterilizing tools, and a GPS communicator like a Garmin InReach round out the safety essentials. Mountain races often add rain jackets, warm layers, and extra food to their mandatory gear lists.
The Sport’s Iconic Races
A handful of races define ultra running’s culture and ambitions. The Western States Endurance Run, held in California’s Sierra Nevada, is widely considered the birthplace of 100-mile racing. It started in 1974, evolved from a horse race, and today accepts only 369 runners selected through a lottery system so competitive that many apply for years before getting in.
The Ultra-Trail du Mont-Blanc (UTMB), held each August in the Alps around the Mont Blanc massif, has become the sport’s biggest international event. Its 170-kilometer course crosses three countries and climbs roughly 10,000 meters, drawing elite runners from around the world.
The Comrades Marathon in South Africa holds a unique place as the oldest and largest ultra. At roughly 90 kilometers between Durban and Pietermaritzburg (alternating direction each year), it draws around 20,000 runners and has over a century of heritage. Its strict cutoff times and the tradition of thousands of runners singing together at the start line at dawn make it an experience as much as a race.
Who Runs Ultras
Ultra running has historically skewed heavily male, though the gender gap is narrowing. In data covering more than 210,000 finishers of timed ultra events, men outnumbered women by roughly three to one. But women’s participation has been climbing steadily, and the performance gap between sexes has been shrinking in recent years.
The typical ultrarunner is older than you might expect. The average age of finishers has increased over the decades, rising from about 40 years before 1989 to roughly 45 to 46 years in the 2010s. Runners aged 18 to 86 have competed in these events. The sport rewards consistency and the willingness to keep moving when everything hurts, qualities that don’t peak in your twenties.