Our Essential Guide To Running Your First 100K

Plus, 100K training plans for every level.

Running 100K is no joke.

If you’ve conquered a few marathon-length events, you might be intrigued by the notion of going even further.

Stepping up to running any ultramarathon—let alone 100K—requires adjusting mindset, pace, and fuel/hydration strategies. Also, if you are unfamiliar with trail running, you will need to hit the trails as part of your long run training.

Your training program also changes from shorter events by bumping weekly mileage, among other aspects, as you want your body to adapt to running comfortably for hours on end.

And in the end, no matter how much you train, there’s no telling what will happen on race day. Ultrarunning is a completely unique running experience in that way.

Let’s look at the best ways to prepare and train for running 100K – and what to expect along the way.

I also share my three training plans for the 100K run distance—Just Finish, Improver, and Compete—at the end of this post. So, whether this will be your first ultra or you are an experienced runner and have run 100K before, there is a plan for you.

how to run 100k training plan

100K Ultramarathon – How To Train and Run

Here are some practical ways you can prepare yourself for the mammoth task of a 100K training cycle:

#1: Train For Time On Your Feet

Hours on your feet are paramount – more important than speed or miles. 

It’s also the biggest commitment you’ll have to make for your 100K preparation. Your body has to get used to being on your feet for hours on end, so it will hold up well come race day. 

There’s no set plan here, but doing a few runs that are 50% of your planned 100k time is recommended. This can mean committing serious chunks of your life (meaning weekends) to running.  

Our 100K training plans below focus on regular training runs and long, slow runs – which you should run at a low rate of perceived exertion.

If it’s your first 100K, you probably don’t have too many time-based aspirations (which is perhaps a good thing – just finishing is an admirable goal when you’re running 100K).

But if you’re training to beat a specific time, you may wish to incorporate some speed work into your training schedule, such as interval training workouts (this is included in our Improver and Compete plans below).


#2: Strength Training For 100K

A 100K run is all about endurance, and muscular strength makes you an endurance monster. 

Many runners can get by running a marathon by doing only running training.

But once you are on your legs for several hours at a time, having some upper leg and core strength really helps you keep your form and fuels your endurance. Remember – your whole body is active while running, not just your legs.  

As a UESCA-certified running coach, I highly recommend strength training a couple of times per week.  If you only have time for one cross-training session, focus on your legs with lunges, squats, and stretching – your body will thank you when you’re 10 hours into the race.

Here’s my complete training guide to weightlifting for runners, which includes recommended exercises, set and rep numbers, and tips.

This was one of the key principles that allowed me to make the leap from 42K to 100K – I focused on strengthening my body rather than just adding more miles to my run training.

100k training plan

#3: Long Runs

Just like marathon prep, you should be factoring in one long, slow, easy run every weekend

As a minimum, you want to have completed at least one 50K before your 100K.  If you are taking things seriously, you want to have covered 70-80kms (50 miler) once, and done several 50Ks (31 mile race).

Remember to build up to these in a structured way rather than going out one weekend and doubling your longest run mileage just to get the run under your belt.  

The trade-off here is balancing the increase in mileage with not getting injured (and finding the time to squeeze in all the training).

Run your long runs at a slow, comfortable, easy conversational pace—sit at just 2-3 out of 10 for RPE. If this is your first one, you’ll see that your race pace will be similar to these long training runs.

Another worthwhile training technique is back-to-backs. This involves running two long runs on consecutive days (still at an easy pace) and getting your body used to running on tired legs.

Related: How To Go From Marathon To Ultramarathon


#4: Tapering For A 100K

Tapering is the age-old marathon training technique of letting your training peak 2 – 4 weeks before your race and gradually backing off. It means you’ve given yourself plenty of time for recovery and preparation for race day.

Tapering minimizes the risk of injury prior to the race and means you should arrive at the start line in the best possible condition with recovered muscles and mind.

However, you’ll often find that it’s harder to apply such a rigid structure to ultra-marathon training. Many seasoned ultra-runners barely taper at all – they might just relax a bit more in the week leading up to the event.

Therefore, your taper length should be determined by how well-conditioned your body is. If you’ve only been distance running for a few months, having a 2-4 week taper before your 100K is worth it.  

This means doing your longest training run in the weeks before the race, then gradually reducing the level of training as race day approaches.

100k training plan, guide, preparation, race to the stones

#5: Pick An Achievable 100K Race

If you’re looking for your first 100K race, do your research and find one that is relatively flat, in a comfortable climate, and well-supported with aid stations and volunteers.

Don’t start by adding things like heat, humidity, or hyenas. That race through the jungle/desert/lava flow will be there next year!

The last thing you want to do is commit to a huge race and DNF because you weren’t prepared enough—this will just discourage you from going again.

“it’s not a sprint marathon, it’s an marathon ultra-marathon

#6: Rate Of Perceived Exertion During The Race

If you have to push yourself in the first 30-40km of a 100K, you’re going too fast. 

It’s natural that as you get fatigued, your body stiffens and tires and you have to force through a bit of pain – but this is different from just standard exertion. 

Your training should have got you to the stage where you can run at a comfortable pace for hours with little strain. I generally stick to a comfortable three out of ten for rate of perceived exertion when running a challenging ultra.

After all, I just want to survive and get to that finish line, not win!

During shorter races like half marathons, you can push your body beyond this comfortable pace, but in 100K races, if you feel yourself going too hard, you have to dial it back, or you put yourself at risk for burnout.

Always remember how far you have left to go and how your body feels.

Related: Ultramarathon Nutrition Guide: What to eat before, during, after an Ultra


#7: Pacing and Splits for 100k 

The ideal 100K run is arguably one that has even splits (a consistent pace throughout). 

As races get longer, it becomes harder to regulate a steady pace – especially when venturing into untouched territory regarding mileage. Your legs get tired and begin to cramp, your energy levels sag, and you can easily lose focus psychologically.

Therefore, run at a pace you feel comfortable with —it should be a pace you feel is very achievable. Much like the 4-hour mark in a marathon, the 12-hour mark is a nice ‘benchmark’ for 100K runners.

But – don’t get sucked in by trying to meet other people’s ideas of expectations.  Run your own race, have a pace and target finish time in mind before you begin, and be ready to adapt. Anything can happen in an ultra, so be ready to solve whatever the race throws at you.

#8: Get a GPS Watch That Will Go The Distance

Most GPS devices have an 8-10hr battery life—simply not enough for your 100K (unless you’re breaking the course record). Though more expensive than normal sports watches, some GPS watches are specifically designed for long-distance events.

I’ve researched the best ones on the market right now – click here for my recommendations (I keep this page up to date with the latest models).

My current weapon of choice is the Coros Apex (here’s my review).

#9: Our Free, Downloadable 100K Ultramarathon Training Plans

I offer three different 100k ultramarathon training plans, based on your ability and goals: Just Finish, Improve, and Compete. Here’s a quick description of each profile, and links below to access the training plans!

100k ultramarathon training plan - just finish

100K Ultramarathon Just Finish Training Plan

Our Just Finish training plans are for runners who simply want to complete their event and get to that finish line. If you don’t want to spend all your free time training and have no specific finishing time or race pace in mind, this is the plan for you.

Our Just Finish training plans usually have more rest days and very little speed work (if any); they’re designed to condition your body to complete the distance, but not to win any medals.

The Just Finish training plans are ideal for completing your first event or for runners with busy lives!

100k ultramarathon training plan improver

100K Ultramarathon Improver Training Plan

Our Improver training plans are for established runners who want to challenge themselves and perhaps set a new PR.

If you’ve already run a distance event, such as a marathon, and want to improve your performance, check out these training plans.  

Our Improver training plans balance training and miles with rest days and (optional) speed work; only include the speed work if you want to improve your base running speed.

If you’ve got some distance running experience and want to push yourself a little, this is the training plan for you.

100k ultramarathon training plan compete

100K Ultramarathon Compete Training Plan

Our Compete training plans are designed for experienced runners who want to challenge themselves, set a new PR, and perform well competitively.

If you’re planning to race and gain a good position, this is the plan for you.

Our Compete plans feature the most intense training regimes – there are a lot of miles in there, different challenging workouts (speed-work), and typically only one rest day per week.

You should only attempt the Compete plan if you are starting from a solid running base and have the time commitment and drive to challenge yourself.

Take Your Training Further With The Ultra Runner’s Playbook

If you’re looking for a deep dive into the world of ultra-running, then check out my Ultra Runner’s Playbook!

The Playbook is my premium course for anyone looking for a complete online ultramarathon coaching solution…

With over 5hrs of video content and a ton of downloadable material, we cover:

  • Detailed daily training plans for ultramarathons based on running ability
  • Ultra training modalities broken down; in other words, how to train smart
  • Ultrarunning strategies for success
  • Expert videos and guides on . . .
    • How to become an injury-free ultra-runner
    • Strength and resistance training for improving performance and reducing injury
    • Fuelling and nutrition for ultrarunners
    • How to achieve your ultramarathon goals
    • Having an ultrarunning mindset
    • Balancing training with your other time commitments
    • Maintaining motivation throughout your ultra journey
Ultra Runner's Playbook

Check Out The Ultra Runner’s Playbook Here!

What about 100-miler?

Photo of author
Thomas Watson is an ultra-runner, UESCA-certified running coach, and the founder of MarathonHandbook.com. His work has been featured in Runner's World, Livestrong.com, MapMyRun, and many other running publications. He likes running interesting races and playing with his two tiny kids. More at his bio.

4 thoughts on “Our Essential Guide To Running Your First 100K”

  1. Hi, Great post. I have a 100km event coming up in about 8 weeks (its technically a walk but I want to apply a run walk strategy to it) and am currently averaging about 40km per week. Any specific tips you could give me?


  2. Hi Matthew, which 100km are you running?

    You probably want to get in a few long walk/runs in the weekends leading up to your run – try and mimic what your body is going to go through on the event – probably somewhere in the 50km range.

    It also depends a lot on your underlying fitness level – if you have never done anything like this before, it will be a long day. Run when you can, but don’t push things. A fast walk can cover a lot of ground quickly – when I have to walk during races, I pretty much do a quick march.

    Another article that might help you a bit:


Leave a Comment

This site uses Akismet to reduce spam. Learn how your comment data is processed.