In the running world, the 10% rule is similar to the Golden Rule. It states that you should never increase your mileage by more than 10% per week.
The trouble with the 10% rule is that it’s not based on scientific data and is not appropriate for all runners. Runners come from all different backgrounds and experiences, and so there is hardly ever a one-size-fits-all approach.
Last year, when I was coming back from a hamstring injury, I became attached to increasing my mileage by 10% every week. However, I kept having setbacks. Why? Because I ignored other considerations such as cutback weeks and the time it took for my tendon to strengthen. The 10% rule did not apply to me.
Conversely, other runners coming back from other types of layoffs can start back faster, whereas new runners may need to increase volume more slowly than 10% a week.
This guide will help you avoid the traps of ramping up too quickly or decreasing mileage too slowly by helping you set a starting point and increase your volume based on your own experience and background
What Is The 10% Rule?
The 10 percent rule simply states that when increasing weekly mileage, you should never increase mileage more than 10% at a time in a week.
Thus, if you’re running 20 miles, you should increase to 22 miles the following week, 24.5 miles the next week, and so on.
The 10% rule ensures that runners increase their mileage conservatively week to week throughout their training program.
The idea behind the rule is to increase your mileage gradually to help reduce the risk of injury. And in that sense, there’s definitely value in taking a cautious, measured approach—especially during certain phases of training.
However, this guideline does not apply to everyone.
So How Valid Is The 10% Rule?
The 10% rule is a bit of an arbitrary guideline.
That’s not to say it doesn’t work—it can be perfectly fine for plenty of runners. But there’s no strong scientific evidence backing it. It also doesn’t consider things like adaptation cycles or the need for cutback weeks, so runners can still end up injured even while following it. (Speaking from experience—I definitely can relate.)
For example, a study on bone restructuring1Franklyn, M., & Oakes, B. (2012). Tibial Stress Injuries: Aetiology, Classification, Biomechanics and the Failure of Bone. In www.intechopen.com. IntechOpen. https://www.intechopen.com/chapters/28466 in response to high-impact exercise, suggests that increasing mileage by 10% every week can make bones weaker for about a month after a new stress while they resorb tissue and remodel the bone structure.
Therefore, it makes sense to wait about a month before increasing training volume to help decrease the risk of running injuries.
Are There Better Ways To Increase Mileage?
Let’s take a look at what legendary running coach Jack Daniels suggests on the matter.
Daniels advocates for increasing mileage based on the “equilibrium” rule. This involves increasing mileage in larger chunks to account for the bone adaptation:
Instead of increasing volume week over week, you would increase about 30% every 3-4 weeks, which would result in about the same volume as if you increased by 10% every week.
Thus, if you are running 20 miles a week, you would increase to about 30 miles the following 3 to 4 weeks. With the 10% rule, in 3 to 4 weeks, you would also arrive at about 30 miles in a month.
By increasing mileage in bigger chunks every few weeks, you get about the same volume while accounting for skeletal adaptations.
Related: How to Train for a Marathon in 3 Months
How Can I Start Increasing Mileage?
When charting their path to increasing mileage, runners should first pinpoint their baseline mileage, which is the current mileage they feel comfortable increasing.
Most training cycles should begin just below your usual baseline to make sure you’re starting with a manageable workload. During this phase, the mileage should still feel easy and well within your comfort zone—so it’s often safe to increase your weekly volume a bit faster than the traditional 10% guideline.
You can safely add 15-20% more per week, at least initially.
With that said, as soon as you get above your baseline mileage, it’s helpful to be more conservative. Rather than adding 10% per week, sometimes it’s best to add 5-10% every other week.
Novice runners should begin by increasing training based on time. Rather than thinking of low mileage and high mileage, think of the total running time per week. In the early stages, it’s just about getting your body used to the work and building some aerobic capacity (endurance).
After 1-2 months, beginner runners can start logging miles and making weekly increases accordingly.
Other Key Factors To Consider When Increasing Mileage
When increasing mileage, it’s essential to incorporate regular cutback weeks, typically every three to five weeks, to help prevent injury and avoid overtraining.
These are lower-volume weeks where your mileage drops to around two-thirds of what you’ve been doing, giving your body time to recover, adapt, and absorb the training load.
A smart way to structure this is by planning your training in cycles: spend the first few weeks gradually increasing mileage and intensity, then follow with a recovery week to reset and prepare for the next block.
It can also be beneficial to repeat a training week, especially once you’ve hit your baseline mileage. This gives your body extra time to adjust to the increased volume and intensity, particularly if you’re newer to running or prone to injury.
Repeating a week of training can provide the necessary buffer to progress safely without pushing too far, too fast.
How should I increase mileage based on experience or injury history?
If an experienced runner is rebuilding to a previous mileage after a post-race recovery, they do not need to follow the 10% rule. Instead, they can increase more rapidly until they return to their baseline mileage, almost like a reverse taper.
The same applies to an injured athlete; after full recovery, they may only need six to eight weeks to return to their previous mileage safely.
If a beginner runner builds to a new mileage, a better system is an increase-adapt pattern, with consistent cutback weeks every four to six weeks.
Beginners can increase up to 15-20%, depending on mileage (higher mileage runners increase a lower percentage per week; lower mileage can increase a higher percentage per week).
This allows the musculoskeletal system to better adapt to the demands of increased mileage and to try and keep runners injury-free.
What Is An Example Of A Mileage Building Process?
Here is an example of a runner building from a baseline of 30 miles per week to 40 miles per week:
- Week 1: 30 miles
- Week 2: 34 miles
- Week 3: 34 miles (repeat week)
- Week 4: 38 miles
- Week 5: 30 miles (cutback week)
- Week 6: 38 miles
- Week 7: 40 miles
Related: Check out my Marathon Training Plans
How Should I Increase Mileage When Introducing New Stimuli Like Hills Or Speed?
When introducing new stimuli like speed, duration of quality workouts, or hills for the first time or the first time in a long time, it’s important not to increase mileage at the same time.
You want to maintain your mileage for a few weeks as your body adapts to the new stressor. For injury-prone runners or fast-twitch runners who fatigue easily with higher mileage, the better choice may be to temporarily decrease mileage while introducing a new stimulus.
You should focus on just one stressor at a time to not overload your body.
When you do add intensity to your training week, be sure to follow one of the most important rules: run easy on easy days to truly recover and hard on hard days to provide stress to the system.
When you give recovery the same amount of attention as running, your workouts will flourish, and you’ll be a better, stronger runner.
Increasing mileage gradually is a great way to help avoid overuse injuries, whether you are training for the New York marathon, a half marathon, an Olympic triathlon, or any other distance for that matter.
For a closer look at some tell-tale signs you are on the brink of an injury and may need a break, check out our next guide:
