The 5% Rule And How To Build Up Your Running Mileage

Are you a runner who realises that more mileage makes you faster? So you want to build up the weekly amount of running kilometres that you make? Let’s take a look at how this is best done and what the science says about mileage and avoiding injuries.

1. Does increasing mileage make me faster?

The short answer: yes, it probably does.

As a coach, I always get annoyed when people talked about ‘doing quality over quantity’. As if the two are not related. Sure, I get it. You want to focus on doing two or three quality workouts per week. But that doesn’t mean you can’t ALSO do easy mileage.

If we look at the training programs of elite runners, I think the truth is very simple. The best runners in the world do two or three hard workouts and fill the rest of the week with as much easy mileage as they can. Elite marathon runners typically run 160 – 240 kilometre per week. And even if we look at those that are in the Olympic final of the 1500m – an event that takes less than 3 minutes – we see that most of them train more than 100km per week, with world record holder Faith Kipyegon typically running weeks of 150km or more in her build up (and by the way; even doing longruns of 40km!).

Jakob Ingebrigtsen — Source: World Athletics

World record holder and Olympic champion Jakob Ingebrigtsen was asked recently: Do you think most runners benefit more from higher volume (more mileage) or from better execution of key sessions? His answer was: “Definitely higher volume”.

He then went on to say: “Higher volume gets you working on your strength, endurance. You become a better runner, you recover faster and it can allow you to do more specific sessions”.

Let me explain what Jakob meant there. Doing lots of easy running creates adaptations in your body, such as the production of more mitochondria in your muscle cells and creating more capillaries (tiny blood vessels) that transport oxygen to your muscles. These adaptations help you to handle the hard workouts better. Doing lots of easy mileage, enables you to do harder workouts, recover well from them and improve. Without the easy mileage, the hard workouts would not have the same effect.

Of course, not everyone responds in the same way to mileage. Some runners benefit immensely from increasing their volume, while others benefit just a bit. But from my experience as a running coach, increasing mileage is one of the training tools that works best for most runners.

2. What is the 5% rule?

The 5% rule says that, in order to build up carefully with less risk of injuries, we should increase mileage by not more than 5% per week. So that means if I’m used to running 50km per week, and I decide to increase my training load, I should start with a week of 52.5km. And then the following week can be 55km and so on.

It also means that if I’m coming back from an injury, and I currently run 20km per week, I should spend about 9 weeks building up from 20km to 30km per week.

What do I think of this 5% rule? It doesn’t make a lot of sense.

Let’s look at two examples.

• I have been training 50km per week for the last 3 years. Now I have some time off so I decide to increase my mileage. Using the 5% rule, I will be running 94km after 3 months. And after another 3 months of building up, I will be at 177km per week. Even if I would take a recovery week every 4^th week, I would still be at a WAY too high volume after 6 months of training. It takes most runners 10 years to build up to 160km per week or more.

• I am used to running 70km per week. I was injured for 3 months and recently started running again. My last week was 20km in running mileage. Using the 5% rule, it will take me 6 months to come back to 70km per week. For most runners, this is absolutely unnecessary and can be done a lot quicker.

The good thing with the 5% rule is the principle it stands for: building up mileage should always be done gradually. You don’t go from 50 to 100km per week within 2-3 weeks. That’s correct. But like most ‘rules’, you should not take this literally. Just because you increase with 5% per week, doesn’t mean you are building up in a smart way.

3. What does the science say about running mileage?

In 2025 a great study was done by Schuster Brandt Frandsen et al. The title of their study: How much running is too much? Identifying high-risk running sessions in a 5200-cohort study. Check it out, you can download it for free.

They took running data from 5205 runners out of many different countries (but mostly based in Europe and Northern America) and followed them for 18 months. From those 5205 runners, a total of 1820 or 35% experienced a running related injury. Then they started checking the data, and tried to find out if there was any relationship between their mileage, and the injury.

They compared 3 things:

1. The length of one session, compared with other sessions in the previous 30 days

   
   

2. The ACWR which is the Acute Chronic Workload Ratio. This compares the mileage of one week of running, with the average mileage in the 3 weeks before that. It’s an often used tool to compare your current training load with your regular training load.

   
   

3. The week to week ratio, comparing every week with the week before.

What they found was different from what you would expect. They found that:

• A significant increase in injury risk was found when runners increased the distance of a single session by 10% or more, compared with their longest run in the last 30 days

• There was a reduced injury risk when runners increased their weekly mileage compared with the 3 weeks before.

• There was no significant effect when runners increased their weekly mileage with 10-100% compared with the previous week.

Let’s first take a look at the weekly mileage. It’s really quite interesting, because it’s the opposite of what the 5% rule says. A 10-30% increase of mileage in a single week (compared with the previous 3 weeks) was associated with a LOWER injury risk. In fact, the larger the increase in weekly mileage, the lower the injury risk. The lowest injury risk was associated with a 100% increase in weekly mileage.

It goes too far to say that we should all increase our mileage by 100%, because overuse injuries can also develop over time, but it is definitely very interesting that there was no connection at all between getting injured and increasing the weekly volume.

The study also identified a clear risk: increase the length of a single running session by 10% or more. A small spike was described as increasing the length of your run by 10-30% compared with your longest run in the last 30 days. Doing this caused a 64% increase in injury risk. A large spike, which would be to double the length of your longest run in the last 30 days, caused an increase of more than 120% in injury risk.

In other words, if you are used to doing 20K longruns, suddenly going for a 23K run increases your risk of getting injured. At the same time, increasing your weekly mileage by 15% does not have this effect at all.

Or imagine you are building up after an injury, and you can run 20 minutes today. That’s your longest run in the last month. Don’t go for 30-40 minutes in your next run! Go for 21 – 22 minutes and build up from there.

4. How do I build up mileage in the smartest way?

First of all, let me tell you what the first question is that I ask my athletes, when they say they want to build up their mileage. I ask them: can we also increase your recovery? Will you spend less time working? Can you increase your sleep from 7 to 8 hours per night? Can you drive a bit less? In order words; if we increase the training load, then how do we balance that with more recovery? After all, it’s training stress + recovery that leads to progress. Not just training stress.

I want you to keep this in mind every time you plan to increase your training load.

Let me tell you a personal story. When I finished university, back in the year 2000, I was 24 years old and ran around 100 – 120km per week. That’s what I could handle. I looked at the elite marathon runners and saw that most of them were doing around 200km per week. I figured that it would be impossible for me to run that much, if I would take a full time job. So I decided to only apply for part time jobs. That way I would train every day in the morning, and again the evening. In between I would take a nap (say from 9.30 to 11.30) and then work for 4-5 hours. This way I could balance training, work and recovery. I slept for 8-9 hours at night and another 2 hours during the day. It enabled me to increase my mileage up to 180km per week when I was 28 years old.

If I had not chosen to work part time, I would have never been able to increase my mileage that much, and I would have never run a 2h12 marathon.

When it comes to increasing mileage, here are my top 5 tips:

• Don’t just increase mileage, but go up and down. One week you increase the mileage, the next week you go down, the following week you increase it again. Sometimes you can increase the mileage two weeks in a row, but don’t keep on increasing your mileage into new territories for five consecutive weeks. I think that is just too risky. An example of a runner who is used to weeks of 70km, and is now trying to increase her volume: 75km – 65km – 77km – 68km – 71km – 79km – 73km – 65km – 80km – 74km. This way you teach your body to get used to a higher volume week, and you also give it time to recover from it.

• Count your average mileage within 4-6 weeks and compare this with what you used to do. It’s hard to give an exact number, but typically a 30% increase within one year is enough for a well-trained runner. This means, for example, going from an average of 70km per week to 91km per week. If you’re new to running and come from a very low mileage (for example 20km per week) this rule doesn’t apply to you.

• Change one thing at a time. Don’t try to increase your training load in multiple ways within the same week. If your focus is on increasing mileage, don’t start increasing the speed of your sessions as well, or adding in an extra workout, or two new strength sessions.

• Always try to be in touch with your body and be flexible with the program. Monitor how you feel in this period of increased volume, also on easier weeks. Sometimes the easier weeks are when you feel it. When you’re getting too tired, or you feel a niggle coming up (or worse; an injury) don’t stick to the program, but adjust. Consistency is always more important than making one week of incredible mileage. So cut back on the mileage for this week, so that you can continue building up.

• Focus extra on recovery. Make sure you fuel well (don’t make the mistake to combine more mileage with less calories!), especially after workouts. Take enough rest, and try to stand less during the day.

• Be careful with the length of your longrun. See the scientific study that I mentioned. The biggest risk is increasing the length of one run too much. It’s much better to increase your mileage by adding 1km or 1 mile here and there, than by adding 5 miles to your longest workout.

Good luck with training and keep the fire burning!

Hugo van den Broek is the founder and head coach of Kenya Camp, based in Iten, Kenya, one of the world’s top high-altitude running destinations. A former elite Dutch marathon runner, he achieved a personal best of 2:12:08 and later became an internationally respected coach. Hugo holds M.Sc. degrees in Human Movement Sciences and Special Education. He lives in Eldoret, Kenya, with his wife, Hilda Kibet, and their three daughters, combining elite coaching with community and athlete development.