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 ultra – let alone 100k – requires an adjustment in your mindset, pace, and fuel/hydration strategies.
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.
And if you are just looking for a 100k training plan, jump to the end of the post!
100k Ultramarathon – How To Train and Run
You can’t just extrapolate a regular marathon training plan to cover the longer distance (maybe you could, but it’d take over your life).
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. 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.
2. Body strengthening for 100k
An 100km 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 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 cross training a couple of times per week, focussing on the upper body. 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.
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 50km 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).
Another worthwhile training technique is back-to-backs. This is running two long 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. 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 100km race, do some research and find one that is relatively flat, in a comfortable climate and well-supported.
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 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.
During shorter races like marathons you can push your body beyond this comfortable pace, but in 100km 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 100km run is arguably one that has equal 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.
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
- Ultra running strategies for success
- Expert videos and guides on . . .
- Having an ultrarunning mindset
- Balancing training with your other time commitments
- Maintaining motivation throughout your ultra journey
- Having an ultrarunning mindset
- 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
- And plenty more expert interviews, articles, and guides!