5 Most Extreme Endurance Challenges You’ve Never Heard Of

If you’re anything like me then you love to watch extreme sports. It’s amazing how much the human body can endure given the right circumstances. As a fitness coach of many years, I’ve come across many different extreme endurance challenges, most of which you’ve probably never heard of. In this article I want to highlight a few truly epic extreme endurance challenges, as well as the athletes that have accomplished them. Keep reading for more.

I plan on showcasing some of the toughest endurances races in the world. I will also cover a few well known records that athletes routinely pit themselves against. Towards the in end of the article I will provide links to some of my endurance related programs, if you feel inspired to tackle some of your own, more feasible endurance challenges.

I want to point out that just because I don’t cover a certain race or challenge doesn’t mean it isn’t a worthy event. After all, the Tour de France is one of the world’s toughest endurance challenges, however almost everyone’s heard of it. I will also say that there are certainly more brutal challenges that I’ll be highlighting further on. Let’s get to our first extreme challenge. The Double Brutal Extreme Triathlon.

The Double Brutal Extreme Triathlon

This even is held in North Wales and attracts some of the best endurance athletes in the world. As the name implies, this event is extreme. For starters, it’s roughly double the distance, compared to normal Ironman Triathlons. If that weren’t enough, the course layout covers some truly extreme terrain.

The event starts with a leisurely 4.8 mile (7.6 km swim) open-water swim. The athletes then transition to a 224 mile (373 km bike) ride, where they will gain roughly 16,000 feet of elevation, cycling around Mt Snowdon. The event finishes with a 40 mile run (up to 84 km run) up and over the same mountain, gaining nearly 10,000 feet of elevation. Here’s a great video from Fergus Crawley as he completed this race in 2022.

Fergus has a great Youtube channel. He also runs a company, Omnia Performance, providing fitness programming for hybrid strength and endurance athletes. From what I’ve seen of his videos he provides some quality programming for folks with unreasonable goals!

The best athletes in the world will finish the Double Brutal in just under 30 hours from start line to finish line. If that wasn’t crazy enough, they plan to do an even longer version next year. In 2023 they will be adding another option to this event, the Triple Brutal! This version is a 7.2 mile swim, 336 mile bike, and a 65 mile run.

Next, let’s talk about one of the most iconic ultra endurance records in North America, speed hiking the Appalachian Trail. Before we get to that record, you should really throw your email down below, so you don’t miss any awesome articles.


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Fastest Known Time: Appalachian Trail

Where as most of these extreme endurance challenges are measured in hours and minutes, this long distance physical challenge is measure in days and months. In the ultra endurance community, well known trails have FKT’s which stands for fastest known times.

Moreover, these records are split between two types of attempts, supported and unsupported. As you saw with Fergus in the Double Brutal, having an amazing support team is key to being able to complete these events. However, there are ultra runners that will self support over the length of this event. Here’s a quick video that highlights the fastest known time for a supported athlete, Karel Sabbe.

Karel, traversed all 2,189 miles of this trail in 41 days, 7 hours, and 39 minutes. In the process he gained over 465,000 feet of elevation! Karel averaged 53 miles per day through the oldest mountain range in the United States, for a month and a half. If that doesn’t impress you, then I don’t know what will! Next, we’re going to talk about one of the most secretive ultra endurance races, the Barkley Marathons.

If you appreciate endurance work, but want to focus on building muscle mass and conditioning, then this is your program.

The Barkley Marathons

The best way to think of the Barkley Marathons is that it’s the Fight Club of endurance races. It isn’t advertised, and there are no publicly known details on how to register for the race. The race itself was inspired by a prison break at a nearby penitentiary, where the prisoner only managed 12 miles before he was caught.

The race director, Gary Cantrell, said he could do at least 100 miles through that terrain, and thus the race was born. This extreme foot race has gone through a few iterations. The current version of the race is as follows.

The race director Gary blows a conch shell anytime he likes from midnight to noon on race day. This signals one hour to start time. He then officially starts the race for the 40 athletes by lighting a cigarette. At this point athletes are free to run the course. Here’s an excellent documentary covering the race.

Each lap of the course is 20 miles or so, and the runners must find a page in a book that has been placed along the route. Their bib number is the page the must find. After every 20 mile loop, they get a new number to look for. Athletes can work together on the course, but no outside assistance can be given as they run.

What makes this one of the toughest foot races is the time cut offs. The Barkley Marathons is nominally a 100 mile race, with 5×20 miles loops. However, you first have to finish 3×20 mile loops in under 40 hours, to be allowed to continue. Runners that fail are treated to a bugler playing taps as the return to the start/finish line in failure.

This race is all about extreme fitness, and the ability to fight through sleep deprivation, as well as the rapidly changing weather conditions in the mountains. To date, only 15 athletes have ever finished the Barkley Marathons under the 60 hour cut off. Next, let’s look at one of the most brutal adventure races.

2021 Adventure Racing World Championship Spain

This is one of the toughest races ,and it isn’t as simple as just a super long run, or triathlon. It’s a true multi discipline team event where teams will have to complete the following: Mountain Biking, Trail Run/ trek, Sea Kayak, River Kayak, Coasteering, Ropes, Navigation.

The event is a total of 600km or 372 miles through some of the roughest terrain imaginable. These teams endured extreme conditions including river crossings, mountain ranges, and challenging weather conditions. Check out this video highlighting this event.

The winning time for this event, in 2021, was 4 days, 1 hour, and 55 minutes. Give the video watch as it explains each of the seven different segments of the race. Personally, I really enjoyed the team work aspects of the race. Now let’s look at our final extreme endurance challenge, Marathon des Sables.

If you want to work on equal parts conditioning and functional fitness then check this program out.

Marathon des Sables

The Marathon des Sables is an ultra endurance race that covers 156 miles in 6 stages. I should also mention that it’s run through the Sahara Desert, in Morocco. Obviously, extreme weather, like sand storms, and temperatures over 120 degrees Fahrenheit are common place. Here’s a cool documentary about it.

This race has been billed as one of the world’s toughest foot races, in one of the worlds most remote locations. Athletes run during the day, and are allowed to rest, and treat their injuries at night. During each segment the athletes hit required checkpoints where they can refill on water.

Each athlete is also required to carry a minimum weight of equipment (between 6-15kg) on the course at all times. This weight does not include water weight. Not only are these athletes running in the most extreme desert conditions, they have to carry a ruck as well!

Now that you’re inspired to work on some endurance training, let’s cover some of my endurance and hybrid endurance training programs.

Endurance Programing

If you’ve taken a look at any of my programs, you’ll know that most them are for functional fitness athletes. However, I’ve got several program that combine lifting and endurance work for those that want the best of both worlds. Check out the list below for some of my more popular endurance programs.



The 12 Week Functional Endurance Program is my most endurance related program. It’s ideal for folks that like endurance events that last around an hour or so. If you’re training for a marathon, or other long endurance event, you should look at a specific endurance program.

That doesn’t mean you shouldn’t lift heavy, as research shows time and again, that heavy strength training improves speed at all endurance related activities. If you are a true endurance athlete, and want to add in some strength training, then check out my 4 Day Strength Split Program. It should integrate nicely with your endurance work.

Mountain make for some of the most extreme endurance challenges

Final Thoughts

These are 5 of the most extreme endurance challenges, and my hat is off to the athletes who have the guts to put themselves through these events. I want to encourage you to challenge yourself in much the same way these athletes have.

If you watch these videos, you’ll see a common theme. Many of the athletes start these races not knowing if they can finish them. I encourage you to find a real challenge, that you aren’t sure if you can finish, and get out of your comfort zone. I bet you’ll be surprised what you can accomplish, if you put your mind to it.

As always, if you have any comments or questions, put them in the comments section below, and I’ll get you a response. Now get out there and get training!


The opinions and information expressed in this article are solely those of the author and are not affiliated with any corporation, group, public or private entity. This web site is not endorsed by, directly affiliated with, maintained, authorized, or sponsored by Crossfit Inc. All product and company names are the registered trademarks of their original owners. The use of any trade name or trademark is for identification and reference purposes only and does not imply any association with the trademark holder of their product brand.

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