Training for Your First 100-Miler: A Quick Intro Guide


Running 100 miles is one of the chief goals of trail and ultra running. While many runners will be content with more “achievable” personal goals, the 100-mile race is the Holy Grail for lots of us as we increase weekly mileage and overcome milestones in our training. And, from the increasing numbers of people signing up to run ultramarathon distances (345% in the last 10 years according to a recent study!), it looks like training for a 100-miler is only set to become even more common. 

How can you prepare for your first 100-mile race day? What do you need to know about nutrition strategy and kit particularities that don’t apply to shorter races? And what is the best training approach for running 100 miles?

Of course, this is a huge topic, but we’ll cover some essentials for your first 100-miler training plan below. Find out:

  • What the specifics of training for a 100-mile race entail
  • How to prepare for your first 100-miler – beyond the training runs
  • Race day tips to help you survive and thrive

What Is Different About Training for a 100-Miler?

different about ultra distanceThe 100-mile distance is more than just a round number. While preparing to run ultras can appear to be just a question of increasing your weekly mileage and being ready to run a long way, it is so much more than that. As you embark on this type of endurance race, you will be on the course for over 15 hours, sometimes even up to 48 hours (the world’s most famous 100-miler, the Ultra Trail du Mont Blanc, has a finishing time cut-off of 46.5 hours!).  

So, what does your body go through during this sort of race, and how should you prepare?

How Your Body Handles the 100-Mile Distance

When we talk about running 100 miles, we need to switch from the distance itself to thinking about the time on feet (or time on the course). For average trail runners (or road runners, for that matter!), this distance will take around 20-odd hours to complete on a flat-ish course, and upwards of 30 hours on hilly, mountainous terrain. Here’s a brief overview of what you can expect to go through as a result:

  • Brain strain. Beyond some risks such as heatstroke from being out too long on a hot day, the brain also has to handle being awake for long periods of time – sometimes, for the whole race. Some runners swear by taking short “trail naps” which can last even only 5 minutes to refresh their concentration and boost their mental capacity. This is because fatigue and lack of sleep will combine to deprive your brain of its cognitive abilities. The result? Hallucinations, poor decision making, slowing down…
    • One way to cope with this is to train yourself to function on little sleep, or when tired. Many ultrarunners go out for a long run after a full day’s work, or practice doing night runs (this also helps you practice using a headlamp, one of the essential pieces of kit in most ultra races).
  • Vision troubles. Professional runner and ultramarathon legend Courtney Dauwalter found herself losing her vision during the Run Rabbit Run 100 mile ultra in 2017. While this is a rare occurrence, studies show that a “painless clouding of vision” can come up and this is something you should be aware of (depending on your overall health condition, too). Moreover, eyes get sore and dry – especially when running in hot and dry conditions. It can be helpful to have some eye drops in your running pack or drop bag if you’ve experienced this in the past.
  • Dehydration. Running ultra distances creates a challenging situation: you need to stay well hydrated, while also taking care not too drink too much and risk hyponatremia. The best way to cope with this conundrum is to develop hydration and nutrition strategies from your training runs, practice to see what works best for you, and adapt to the climate, weather conditions, and the situation on the day. 
  • Stomach issues. As the race progresses, continuous intake of various nutritional products may lead to GI (gastro-intestinal) issues. You will need to consider mixing in real food in the form of sandwiches, aid station food, and anything else that works for you. If for no other reason, variety is key to keeping you interested in eating after 12+ hours on a course! And, without eating, you will run out of energy, so there’s no option to simply skip nutrition.
  • Legs and feet. There is no way around it, your legs and feet will hurt during a 100-miler. Firstly, be prepared for the pain. Secondly, prepare for crises which WILL come up, such as blisters and swollen feet. A good idea is to do a few runs over 6 hours long in training, and some training races that can put your body through the same stress as your goal race will. This will show you how your feet deal with your choice of socks and shoes, and how to treat your blisters or anything else that may come up. This is a massively personal choice, but the book “Fixing Your Feet” by John Vonhof (Amazon)offers lots of helpful advice for preparation and treatment, so start there if you have no clue what to do.

Adapt Your Training for a 100-Miler

Now that you know how running a 100-mile race will take its toll on you, how can you adapt your training? Here are a few tips that will help you avoid some common mistakes, too.

Embrace Walking

To increase the number of miles per week in a manageable way and to avoid too much strain on your joints, you can add fast walking and power hikes into your training plan. This is actually really beneficial, as in most long ultras, up to half the time is spent at what can be considered a walking pace (below 4 miles per hour). And the more efficient you are at power walking up those hills, the better your result will be!

When you go on long runs, pick routes with similar elevation and terrain as your race, and practice pacing yourself on the climbs as you would on race day. This may mean power walking almost every climb, to preserve your legs as much as possible. 

Additionally, if you are preparing for a mountain ultra, spend time simply hiking in the mountains. It will get you used to the altitude, the terrain, and the area you’re going to be racing in (if you can do a race ahead of time, that’s ideal!). Hiking means more time on your feet, which builds your endurance and strength. Bonus points for wearing a heavier backpack, building strength in your upper body which will make the race pack (with lots of additional mandatory kit) not so heavy at all.

Focus on Time on Feet

A lot of people wrongly fixate on the weekly mileage volume when training for ultras. Yes, volume is important, and you should increase it gradually. But, if you’re running 100 miles, you don’t need to be doing 100 miles per week in training every week!

Instead, it’s a good idea to plan your running around time on feet and intensity (think heart rate training and quality workouts). It’s good to be able to run at least 60 miles per week in training and you should aim to mimic the feet of elevation gain of your course, as well. However, there is no set “magic” number of miles you have to cover to finish a 100-miler and, remember, you won’t be running the entire time!

Combining hiking and active recovery walks with your training runs will give you more time on your feet, more distance and elevation, and ultimately a better, more well-rounded preparation for your race.

Prepare for a Long Day(s)

100 miler preparationOne thing you need to account for when training for a race that will take over 15 or 20 hours is that there are lots of additional variables you might not be able to replicate beforehand. Weather is a huge factor, and you should expect to at least be able to change your clothing or layer up as you go from day into night (or the opposite, if your race starts in the evening or very early morning and then heats up).

Additionally, mountain weather can change even more dramatically and quickly within a day. If possible, try to do a few long runs in the mountains in training, to experience the motions of having to stop, put on warm clothing, re-arrange your pack etc. It’s also important to learn your body’s signals and know when you need to change your clothing (i.e. don’t wait until your hands are already frozen!).

Testing Your Nutrition

The other tricky thing about such a long event is the nutrition, as we’ve mentioned above. Solid food will win over gels and energy drinks almost every time once you’ve gone over a number of hours. Additionally, night running can confuse your body’s self-regulation mechanisms, so you might find it harder to eat late at night. This is, again, where practice comes in.

In training, experiment with various sources of energy: from a humble cheese sandwich or mashed potatoes to a quick pit stop where you have a slice of pizza, anything goes! Make sure whatever you go for sits well in your stomach. But, remember after so many hours out on the trails, you enter uncharted territory for your digestive system, too. You may find that things you tried in training don’t work, or that you are unable to keep anything down. This is where mental fortitude also plays a role.

Mental Toughness Training

No ultramarathon training plan skips the mental aspect. Dealing with extreme fatigue, sleepless nights, long bouts of effort and possible digestive discomfort can present incredible challenges in ultras. This is why you need to set time aside for mental preparation during your training, just like you do for your training runs.

Addie Bracy’s book (found here on Amazon) “Mental Training for Ultrarunning” gives some very good tools to guide you through this type of preparation and we would encourage you to book time during your rest days to work through the areas that you feel you need to develop. Either from your experience with longer distance runs in training, or from previous ultra races, you’ll have identified the times when you’re likely to struggle and the reasons for it. Take some time to address those and develop mental toughness before tackling 100 miles.

Knowing the Course

We’ve said it before, but it bears repeating, knowing the course and preparing for it very specifically is one of the keys of ultrarunning success, especially for 100 miles and beyond.

Here are some key things you need to look out for and how to translate them into your ultramarathon training plan:

  • Train for the course profile. This means taking into account the vertical gain, the type of terrain, and the overall conditions. Will you be running on rocky trails or on smooth grass most of the time? Will you have very steep descents, or are they gradual and runnable? Do the climbs require you to use hiking poles? Knowing all this in advance – by studying the race map, but also reading race reports and checking out the race on social media – will allow you to mimic as much as possible of race day during your long runs and learn how all of it can impact your performance.
  • Train for the climate. We’ve said it before, but you need to prepare for either hot or cold temperatures, especially if you don’t live in the same area as the race. Look into heat training for summer races if you will face a serious heat difference from where you live.
  • Make an aid station plan. Some races will let you have crew helping out at aid stations, while some will maybe only let you have a drop bag at specific points. In all these cases, it’s good to make checklists in advance and visualize what you will need as you get to each designated point. Give your assistants the lists to ensure you don’t leave without all the food or kit you need from each stop. Take the pressure off yourself on race day by having all this sorted in advance, so you don’t need to lose any more mental energy on it then.

Race Day Survival Tips

You’ve done the training and the pre-race preparation, now all that’s left is enjoying the day! 100-milers tend to have a bit of a festival atmosphere, so it’s important to remember to have some fun. And here are some extra survival tips to take you all the way to the finish line:

  • Eat a lot, and slowly. Set an alarm on your watch to remind you to have something every 20 or 30 minutes. Even later in the race when you might not feel like eating, use this time to sip on a carb drink or Coke. It all makes a difference.
  • Pace, pace, pace. Remember you have a long day ahead of you. If you go out too hard, you risk running out of energy. Have a timing plan and stick to it.
  • Mantras and motivation. Why are you doing the race? What’s going to get you through the dark patches? Write some motivating mantras or practice them in training. If the race allows, play some music when you’re down or tired. Any bit of mental boost will make a huge difference.
  • Prepare to feel bad. No one gets through 100 miles without any pain or suffering! As long as you prepare to have some bad times, it will be easier to deal with them when they come. Consider what you’ll do when some usual suspects hit: how will you deal with blisters, with stomach cramps, with sunburn? Having a plan beforehand will make you more efficient at dealing with these things and it will also make them feel less daunting if they do happen to you.
  • Never decide to drop out before an aid station. Final tip: you’re very likely to want to drop out at the next aid station at some point during the race. Instead of making a plan to quit, do the opposite: get ready to use the next aid station to prepare the rest of your race. See yourself going in, getting some nutrition for runners, changing clothes or shoes, resting for a few minutes, restocking, and heading back out. Once you’re out, do you still feel like quitting? 9 times out of 10 the answer is no, and you’ll be happy you made the decision to carry on!

Succeeding in Your First 100-Miler

A race as long as 100 miles requires a lot of preparation, both physically and mentally, but the good news is that the increasing popularity of long-distance running has led to there being a wealth of resources around how to tackle it. All the principles of good road and trail running training still apply: increase mileage progressively, cross-train and respect recovery time, and listen to your body.

For 100 miles, specific training is more important than ever, as is mental training. Have a race plan, execute it calmly on the day, and remember to enjoy the process and the experience!

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