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.
100 kilometers is 62.14 miles, to put it in perspective.
Your training also changes too, as you want to adapt your body to get used 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. Ultramarathons are a completely unique experience in that way.
A 100km ultramarathon is a serious test of your mettle!
Let’s look at the best ways to prepare and train for running 100k – and what to expect.
I also share my three training plans for the 100k run distance – Just Finish, Improver, and Compete – at the end of this post.
100k Ultramarathon – How To Train and Run
You can’t just extrapolate a regular marathon training plan to cover the longer distance. For one, it’d take over your life. It would also be waayy to many miles.
In reality, you have to condition your body to get used to long hours on your feet, while not over-training.
Here’s some practical ways you can prepare yourself for this mammoth task:
1. Train For Time on your feet
Hours on your feet is paramount – more important than speed or miles.
It’s also the biggest commitment you’ll have to give for your 100k preparation. Your body has to get used to being on your feet for hours on end, so it holds 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 probably 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 training such as interval training (this is included in our Improver and Compete plans below).
- Related: 10 Lessons I Learned From My First 100k, By Maria Andrews
2. Body strengthening for 100k
An 100k run is all about endurance, and muscular strength makes you an endurance monster.
Many runners can get by with marathon-length runs 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. I highly recommend doing 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 10hrs into the race.
Here’s my complete 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 42km to 100km in one race – I focussed on strengthening my body rather than just adding more miles to my run training.
3. Long runs
Just like marathon prep, you should be factoring in one long, slow 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 70-80km once, and done several 50kms.
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, conversational pace – sit at just 2-3 out of 10 for RPE.
Another worthwhile training technique is back-to-backs. This is running two longer runs on consecutive days. This technique gets your body used to running on tired legs.
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’s a technique that means you’ve given yourself plenty of time for preparation.
Tapering minimises the risk of injury prior to the race and means you should arrive at the start line in the best possible condition; your muscles recover and your glycogen stores get refilled.
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.
Your taper length should therefore be determined by how well conditioned you body is. If you’ve only been distance running for a few months, it is worth having a 2-4 week taper before your 100km.
This means doing your longest training run in the weeks before the race, then gradually reducing the level of training as race day approaches.
5. Pick an achievable 100k
If you’re looking for your first 100k race, do some research and find one that is relatively flat, in a comfortable climate and well-supported.
The last thing you want to do is to 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. Exertion during the race
If you find yourself having 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 3 out of 10 for Rate of Perceived Exertion when running a challenging ultra. After all, I just want to survive, 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 really have to dial it back.
Always bear in mind how far you have left to go, and how your body feels.
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 you are venturing into untouched territory regarding mileage.
Your legs get tired and begin to cramp, your energy levels sag and psychologically it’s easy to lose focus.
Therefore run at a pace you feel comfortable, it should be a pace you feel is very achievable. Much like the 4hr mark in a marathon, the 12hr mark is seen as a nice ‘benchmark’ for 100km runners.
But – don’t get sucked in by trying to meet other people’s ideas of expectations. Run your own race, have a pace / target time in mind before you begin, and be adaptable!
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).
9. Our Free, Downloadable 100k Training Plans
I offer three different 100k ultramarathon training plans, based on your ability and goals. These are Just Finish, Improve, and Compete. Here’s a quick description of each profile, and links below to access the training plans!
Our Just Finish training plans are for runners who simply want to complete their event. If you don’t want to spend all your free time training, and have no specific finishing time 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!
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.
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’s 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 really challenge yourself.
Here are some further resources I think you’ll find useful in preparing for your 1st 100k:
- 7 Bizarre and Interesting Facts from the World of Ultrarunning
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!
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- Expert videos and guides on . . .
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- Balancing training with your other time commitments
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- How to become an injury-free ultra-runner
- Strength and resistance training for improving performance and reducing injury
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Take Your Running Further With Our Resources...
Half Marathon Resources
Marathon Training Resources
Ultramarathon Training Resources