What is the Optimal Strategy for Increasing Mileage to Avoid Injury: Research on the 10-Percent Rule and Down Weeks

When it comes to your week-to-week training progression, there are a range of options.

Some runners charge headlong into higher mileage and intensity, relying on their body to signal before an injury or complication develops.

Others adhere to a rigid plan — the best known being the “10-percent rule,” which dictates increasing the mileage each week by no more than 10 percent.

There are, however, other “rules” you could follow.

Jack Daniels, of Daniels’ Running Formula and VDOT fame, advocates increasing mileage by 20 or 30 percent and stabilizing for three to four weeks before increasing again. You could call this the “equilibrium” approach.

Still others prefer designating every third or fourth “down week” for recovery.

Each method has benefits and drawbacks. Sop, let’s examine some of the pros and cons of each method and look to scientific literature to help define what might be best for you.

The pros and cons of mileage progression methods

The advantage of “running by feel” is that you aren’t held down by any charts or tables.  And, if your body is on the same page as your ambitions as far as what level of training you’re ready for, you can progress as quickly as possible to your ideal level of training.

But this is a big if.  Many runners, myself included, have found that their ambitions get the better of them and cause them to charge headlong into increases in mileage and intensity that are, in retrospect, far too great, leading to injury.

The particulars of your own response to increased mileage are unique, though, so you may be able to cruise through lower mileage levels without any sort of predetermined plan until you approach higher realms of training.  Or perhaps you’re one of the lucky few who seem to be indestructible, only succumbing to illness or the odd ankle sprain.

For the rest of us, there are the rules for increasing mileage.

The 10-percent rule

The 10-percent rule is simple (though the measurement is arbitrary—no study has showed that it is superior to an 8 percent or a 12 percent rule), and from the accumulated experience of runners and coaches, a fairly safe option for many athletes.

The week-to-week progression is pretty easy, and it poses a linear ladder of training that you can climb. Starting from 30 miles a week, for example, you can progress to 33, 36, 40, 44, 48, and so on. The only problem with the 10-percent rule is that it ignores some of the basic theoretical principles of exercise physiology.

There’s little allowance for adaptation and supercompensation—if your body’s timeframe for adapting to a new level of training is longer than a week, you’ll start to slide backwards.

Additionally, there is scientific data derived from bone injury studies that the body typically does not adapt on a structural level as quickly at a high training volume. On the flip side, there’s also evidence that mileage increases of up to 20 percent per week are safe when running at low volumes, 10 – 20 miles per week.

The equilibrium method

Considering this, an “equilibrium” rule, as Jack Daniels advocates, makes more sense.  By increasing your volume in larger chunks, then maintaining it for several weeks, you achieve nearly the same overall long-term mileage progression, but with an allowance for your body to adapt to the new stress.

Under a plan like this, you would increase your mileage from 30 to 42 all at once, then maintain 42 miles per week for three or four weeks, then increase it again to 55.

Research on bone restructuring in response to high-impact exercise (like running) has shown that bones are actually weaker for about a month after a new stress, while they resorb tissue and remodel the bone structure.²  The Daniels equilibrium model allows time for the bones of your foot and shin to become stronger before you introduce a new stress.

It also respects the law of supercompensation, which dictates that adequate time is needed to adapt to a new stress before improvement will occur.

The down week approach

Another option that corresponds to the physiology and tissue remodeling principle is the “down week” approach. Under this model, you can increase your weekly mileage every week (perhaps by 10 or 12%), but every third or fourth week, you take a “down week” at a lower volume to recover before progressing onward.  So, your mileage progression might be 30, 33, 36, 30, 40, 44, and so on.

The down week approach is popular among high-mileage runners who often feel that continually plugging away at triple-digit volumes leaves them exhausted and prone to injury. Taking a 10- or 20-percent down week allows you to recharge and block injury development.

Like the equilibrium approach, the down week method allows the bones to remodel to new stresses. Unfortunately, researchers have not defined a precise time frame for physiological muscle and tendon remodeling and the plan may require adjustments.

A minority of runners can run by feel and remain healthy, and others that utilize the headstrong approach experience over-training or injury, but for most, planning out a mileage progression, independently or with a coach, is a significant training element.

Final points

• Ideally, all pre-determined plans would also incorporate listening to the body for stress signals and adjusting the details as necessary.

• Regarding intensity, in theory, a similar gradual progression rule should apply, but planning a concrete plan involves considering more variables and consulting a professional may be necessary.

• When it comes to sketching out training progression, allow time for your body to adapt to new stress levels. If you begin at 30 miles per week, but have experience training at 50 miles, using the old-fashioned 10-percent rule to move from 30 to 50 would probably work out well.

• But transitioning into uncharted mileage territory would require using the equilibrium or down-week model to allow for physiological stress adaption, particularly essential if you have a shin or foot bone injury history.