The 10 Percent Rule: Fact Or Fiction?

Some runners may benefit from breaking the rules of this common training concept
Staff Writer

Jeff Gaudette— Pick up any book on running and you’ll probably find a reference to the sacred 10 percent rule. In case you haven’t heard, the 10 percent rule states that to stay injury-free in training, never increase your mileage by more than 10 percent in any given week.

Certainly, increasing your overall mileage by only a few miles per week seems like it should be a foolproof plan to injury-free running. However, while I am in full support of cautiously increasing your training load, assigning an arbitrary number to how much you can or should increase your training each week is a bit disingenuous.

I wish I could tell you where the evidence or initial support for the 10 percent “rule” began. Perhaps it stems from our affinity for catchy headlines and snappy, simplistic advice. Regardless of how or why the 10 percent principle became so popular, it’s time to expose the myth and structure your training around more individualized advice.

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Emphatically Debunking The 10 percent Rule
Coaches like me are always looking for scientific evidence to support our assumptions. While it’s important to be careful when extrapolating results and advice from tightly controlled experimental conditions, studies can be very useful when it comes to generalized principles. Unfortunately for proponents of the 10 percent rule, science is not on their side.

In 2007, a group of researchers set out to test the effectiveness of the 10 percent rule. The researchers studied 532 novice runners training for a local 4-mile race by assigning half of the runners to a training program that followed the 10 percent rule and the other half to a more aggressive training regimen. Each runner followed the same warmup process and the overall structure of the training was the same — minus the training volumes.

The results? The two groups had the same injury rate — about 1 in 5 runners.

Perplexed by the identical injury rates, the researchers hypothesized that the runners weren’t ready to undertake a training program when they began the study. So they repeated the study, but this time they assigned the group training under the 10 percent principle a 4-week pre-conditioning program. The control group was assigned the same, more aggressive training plan as the initial study with no 4-week buildup.

Again, the results came back with the same injury rate for both running groups, about 1 in 5.

These two studies clearly indicate that prescribing to the 10 percent rule does not reduce your chance of injury. The question now becomes: How do you decide how much can you safely increase your weekly training volume while minimizing injury risk? While the answer is certainly individual, over the following pages we’ll take a look at some more flexible “rules” to follow.

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Mileage Progression Doesn’t Always Have To Be Linear
Driven and dedicated runners always want each training week to be better than the last. Whether that means more mileage or faster times, we want to see the trajectory continually climbing. However, to get fitter each week, your mileage totals don’t necessarily have to follow a linear progression.

Many experienced competitive runners and coaches follow a “3 week up, 1 week down” philosophy, whereby they increase mileage slowly for three weeks and on the fourth week they take a step back and bring their mileage total back to the number at week 1. For example, weekly mileage totals in this situation might look like this: 50, 55, 60, 50, 60, 65, 70, 60 until they build to the maximum amount of mileage they want to maintain.

This is just one example of how you can uniquely structure your mileage buildup. I call the weeks you step back in mileage “down weeks.” Some runners respond well to down weeks every five weeks, while some runners need them every three weeks to stay healthy. The beauty of the system isn’t in the exact formula, rather the notion that mileage progression doesn’t have to follow strict linear increases.

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Consider More Than Just Mileage
If mileage were the only training element runners had to worry about, the world would most certainly be a happier place! Unfortunately, when discussing how to progress training volume, a runner has to consider many factors: intensity, pace, frequency, surface and weather, to name a few. All of these elements can be a factor in how easily and safely you can, and should, progress your training.

For example, in the tepid fall weather, an experienced runner might be able to increase mileage by as much as 30 or 40 percent each week for a month if they are running nothing but easy miles on soft surfaces. On the other hand, runners attempting to tackle a 12-week 10K training plan in the winter will need to be more cautious with their weekly mileage progression since new workouts and different stimuli factor into how much training they can safely handle. So be sure to listen to your body and consider all the elements of your training plan, not just mileage.

We all love the strict and explicit “rules” of training we can easily find in books and magazines because following a strict set of rules makes running simple. However, approaching your mileage build-up in a more holistic manner might actually result in better results. Give it a try.

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