The 10% Rule
Hello followers of the 10% rule! We have a name for you in our business. We call you “Patients”.
Let’s break it down. The 10% rule is ubiquitous. A cursory search on Google will tell you: “Follow the 10% rule! Build your mileage by adding 10% more miles week after week.”
Sounds simple, right? But the truth is that, as with all things, one size does not fit fall. The 10% Rule is good in theory, but shit in practice. There’s no good evidence to support this “rule” and no one can even agree on where this theory came from.
What’s wrong with the 10% rule? Let us count the ways.
But first, a disclaimer…
Before we jump into all the reasons that the 10% Rule sucks, let me acknowledge that there are probably people out there who have used the 10% Rule successfully. You might know one of these people. You might even be one of these people. But these are the outliers. For most runners, new and veteran, the 10% Rule is a recipe for disaster.
So let’s dive in. Why should you not follow the 10% Rule?
You’re probably building mileage too quickly
Let’s say you’re a runner starting out at 20 miles per week. If you’re following the 10% Rule, your next 8 weeks look like this:
Week 1: 20
Week 2: 22
Week 3: 24
Week 4: 27
Week 5: 30
Week 6: 33
Week 7: 36
Week 8: 40
That’s only 10% more miles, week after week. But what that means in practice is that after just 8 weeks, you have a 100% increase in the number of miles you’re running. Is that feasible? Again, maybe. But for most people, probably not. It’s asking your body a lot to double its capacity in just 8 weeks.
If you're reading this and you think that 100% improvement in 8 weeks sounds reasonable – it’s NOT! It’s just not. You’re going to have to believe me on this. I’m a doctor.
Don’t believe me? Okay, let’s dive into that.
Mileage Isn't Everything: Factoring in Stress, Load, and Intensity
Soft Tissue Stress Load: Everybody is different
Just tracking miles (or kilometers!) doesn’t consider the total stress load placed on your tissues. We’re talking about connective tissues like tendons, muscles, bones, and your nervous system as a whole. Let’s break it down.
Nervous system: The fastest learner. Surprise! The majority of your strength increase in the first eight weeks is actually neurological! I’m talking about your brain’s connection to your muscles. In your first 2 months of training, your speedy brain quickly gets better at using your muscles – sending and receiving signals, building a better connection, etc.
Muscles: The fastest strengtheners. All your muscles have their own dedicated blood supply (think, veins and arteries running through all those muscle fibers). This allows your muscles to make big structural gains fast – faster than the rest of your soft tissue can keep up.
Tendons and ligaments: Indispensable, but slow to catch up. Tendons and ligaments usually don’t have their own blood supply. They diffuse blood from other areas, so they heal slower and gain strength less quickly. Tendons and ligaments also don’t have the same building process. They need to change their structure and this can happen over 4-8 weeks.
Run Intensity: Not all runs are created equal!
The 10% Rule also disregards the intensity of the runs that you’re doing. Long runs, tempos, fartleks, and intervals are great tools (especially once you’ve built a solid base), but all place an exponentially higher level of stress on the body over just “base miles”.
Here is my point system for calculating your miles. The 10% Rule assumes all your runs are base runs. This system gives you a clearer idea of what kind of stress you’re putting on your body with different types of runs.
*Disclaimer! I came up with this system on the fly a few years ago during a session. If it’s emulated someone else's intellectual property, please let me know!
**Disclaimer 2: This is NOT meant to be an alternative for calculating a 10%-Rule-ish mile breakdown! This point system is my way of illustrating how off-base the 10% Rule is in JUST looking at distance without taking into account intensity.
In this point system, we’ll assume all base runs are 1 point. Those base runs are easy runs where you can keep your heart rate under 150, or in Zone 1 or 2. (Think: easy, conversational pace, where you can talk but not sing).
Long runs go up by half a point because – even though they should still be done at that conversational pace – you’re running for longer than 75 minutes, building your endurance.
Speed work starts going up a whole point because now we’re also adding increased stress to your musculoskeletal system.
And so on. The more intensity or stress you’re putting into your run, the more points it should be calculated with.
So if we take the 10% Rule, and add the increased value of intense runs, the math starts to look like this: A 5-mile easy run is worth 5 points. But 5 miles of 10k intervals is worth 20! So if you’re following the 10% Rule starting with 5 miles a week and you add in just one 10k interval… suddenly, in one week, you’re increasing the load on your body by 5X!
Your poor body. The best, most positive, ambitious mindset in the world means nothing if your tissues can’t keep up. Do yourself a favor and kiss your 10% Rule goodbye.
How to do it better
So, how would I recommend building mileage?
There truly isn’t a one-size-fits-all approach. Every person is different, with different genetics and experiences and build. So, while I won’t dish out a formula to follow, these are the recommendations I make to people:
Choose a focus. Choose to focus on either mileage or intensity in a week, but not both.
Ease back in from rest. If you’re coming off of a break and you want to add intensity, consider dropping another run so you’re not doubling down (refer to the point system above).
New runners need more time. People who are new to training need more time to adapt to training than seasoned runners. If you’re new to this, don’t model your training after someone who’s been doing this for years.
Work in 3-4 week blocks. Some people think of these at cut-back weeks. Every 3rd or 4th week, drop your overall mileage and intensity (including long runs!) That way, you’ll have 3 weeks of building and a cut-back week to allow your body to rest and adapt.
Don’t use the 10% rule. IMHO.
Want to know more about building a sustainable training plan? Read more about working in 3-4 week training blocks here.