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Base Training for Ultra Runners


By Ian Corless

One season has come to an end, you have relaxed over the Christmas break and a new year arrives with a whole host of possibilities and opportunities. It's time to start your ultra training again. All over the world, runners who participate in endurance events will start base training.

Base training is something that all endurance athletes are familiar with, it's about laying a strong aerobic foundation for the coming years racing. But if you are an experienced ultra runner I question if you need to base train. For me, flipping things on the head now would be a good idea. Drop the distance and time on feet and go short and fast, get some speed back in those one- paced legs and become a fast ultra runner later in the year. I elaborate on this in an article here.

But if you are new to running, new to ultra running or are coming from shorter and faster running, say 5k, 10k and half marathon, base training is for you.

Ultimately at this time of the year (and all times) we should ask:

  • What we're doing and why?
  • What are the real reasons for doing any training?
  • What are the actual objectives we are trying to achieve?

Without understanding your objectives, you will never be able to understand how to structure your training and maybe more importantly, you won't know when you have achieved your goal so that you can then move to the next phase.

So why is 'base training' important? Ask any experienced the runner and they will say one or all of the following:

  • It's about getting the miles in.
  • It's about time on feet.
  • It teaches my body to burn fat.
  • I need endurance.
  • The events I am running are long distance.

So let's break that down and look at those points under 3 key headings:


When competing in endurance events, you need to use fat as a fuel source as the body can only store so much carbohydrate. Ideally at least 50% of the energy you use when running long should come from fat, with the remainder coming from carbohydrate. Base training allows you to run slower, longer and turn fat burning on as a fuel. If you use a higher percentage of carbohydrate as fuel when running, you will eventually run out (even if you try to top them up with energy products) and this will cause you to slow down and possibly stop. We have more information on diet here.


Running for several hours causes damage to muscles, tendons and other tissues. This breakdown causes pain and inflammation and will cause you to slow down and potentially grind to a halt. Base training allows you to progressively adapt your muscles over time with a well structured plan. It's all about building time and on feet and extending one’s ability to endure the demands that running long brings.


Running long is about the mind, focusing on the objectives, controlling external distractions and having the focus to last the distance. If you are only used to running one or two hours, running for four, five, six or longer will be purgatory. Base training helps this adaption.

Things to consider when training

Running at a slower pace and lower intensity teaches your body to use fat as a fuel source. You can enhance this process by running fasted (no food before the run) usually in the morning after sleep or you can eat foods that promote fat usage. If you speed up or increase your effort you will turn to using carbohydrate as fuel, so run slow. Too many run too fast. If in doubt, use a heart rate monitor and/or GPS to keep everything under control.

To clarify:

  1. Runner ‘A’ runs 10-miles in 1 hour, he or she uses 80% carbs and 20% fat to fuel the run. The total calorie burn may well be 800 calories for the hour.
  2. Runner ‘A’ runs 10miles in 2 hours 15 min, he or she uses 80% fat and 20% carb to fuel the run. The total calorie burn may well be 400 calories for 1 hour with a total calorie burn of say 900 calories for the session.

Run hard and you will eventually need to stop, run slower and get the pace right and you will be able to run longer. As you will see from above (very simplistic example) running longer and slower allows you to utilise the almost unlimited fat stores within your body - perfect for ultra runners and multi-day runners.

Base training allows you to progress long runs either in time or miles. I prefer time as distance is often influenced by many other factors, whereas, time on feet is a definitive thing. Also, runners often get obsessed by mileage and stress at the distance covered. In a well structured block of base training your legs will adapt to the repeated stresses but remember rest is important too. Try building time on feet for three weeks and then have one week easy (3/1 training). The following month build again for three weeks and then repeat for the base training phase, say three to four months.

More 'time on feet' will develop your ability to mentally accept the challenge from running long. I'm sure you have heard the term, 'my head just wasn't in it.' Running long is as much about being mentally strong as physically strong.

If you are training for an ultra you can't get away from the fact that you need to adapt to running for longer periods. Running 12-miles at a hard pace is great training for sure, it's fast, you feel good and it's over and done with say 90-120 minutes. But if the race you are training for is 50-miles and you anticipate it to take 12-hours, that 12-mile run is going to be of little use. Going hard uses more carbohydrate, leads to less 'time' on your feet and you become mentally accustomed to exercising for shorter periods of time.

But faster running has a place, particularly for the seasoned and well practiced ultra runner. This is where skipping traditional base training and actually doing speed work and faster sessions when others are base training is a great idea. Yes, speed work instead of base; more on that in another article.

Does that mean ALL running should be slow, steady and long?

If you only ever train easy, you'll end up being slow. But base training in the winter months or at specific periods in a well structured and balanced plan is essential. You just need to know how and when to do it.

If you are new to running, coming from say 5k, 10k, half marathon running or dipping your toes in running longer than a marathon for the first time, base training is almost certainly for you over a well structured 12, 16 or 20 week period using the 3/1 formula.

But as mentioned above, a seasoned runner who can run long, has run ultras for years, has one pace and is looking to go quicker, base training may actually just make you slower and I suggest reversing things around; drop the regular long runs and speed up over shorter distances for a structured period. When you get back to race pace, you'll find it easier to run the same pace or you will find for the same effort, you are running faster.

For a structured training plan, consider Justin Bateman’s Run Ultra 50km programme.

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