Reassessing the 10-Percent Rule
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% 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.
Emphatically debunking the 10% 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 researches 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% rule and the other half to a more aggressive training regimen. Each runner followed the same warm-up 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 researches 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% 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 build-up.
Again, the results came back with the same injury rate for both running groups, about 1 in 5 runners became injured.
These two studies clearly indicate that prescribing to the 10 percent rule does not reduce your chance of injury. The question now is how do we decide how much can you safely increase your weekly training volume while minimizing injury risk? While the answer is certainly individual, here are some more flexible “rules” we like to follow:
1. Mileage progression doesn’t have to be linear
We runners always want each training week to be better than the last. Whether it 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 elite 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, a runner’s mileage totals might look like this: 50, 55, 60, 50, 60, 65, 70, 60 until they build to the maximum mileage they want to hold. Many of the training plans that you use when working with our coaches or our basic plans follow this concept.
This is just one example of how uniquely you can structure you mileage build-up. I call the weeks you step back in mileage scheduled 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.
2. More than just mileage to consider
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, weather – they can all be a factor in how easily and safely you can 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. As coaches, we try our best to help you listen to your body and we 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, which is why we as coaches enjoy breaking this rule.