Busting the 10% rule in endurance sports

It’s long been hypothesized that athletes like runners should increase their training volume by no more than 10% a week. This is generally considered to be one of the golden rules to injury prevention.

But as I’ve constantly revised my own return from injury training plan, and religiously studied the training of elite athletes on Strava, I’ve grown in my curiosity as to whether or not the 10% rule is always necessary.

While it’s evidently a useful concept to avoid overtraining, you can still overtrain from no change at all, or even a decrease in training from one week to the next. Meanwhile, if I’ve consistently run 100k+ weeks throughout the past ten years, why wouldn’t I be capable of a quicker increase back to that point? Why wouldn’t I be capable of bumping up my mileage from 30km to 40km between weeks 4 and 5 of injury rehab without worry?

To bring even more context into the equation, right now I’m training 2-3 days a week, focusing on quality sessions and then giving my body plenty of time to recover for the next session. It’s not necessarily the mileage I have to worry about if my body feels capable of accomplishing long running feats and then recovers efficiently. The 10% rule might become more necessary to follow when I start to run the type of high mileage associated with obscene insanity – around 120k+ weeks.

But for the meantime, my body has already shown signs that it’s able to bounce back faster than the 10% rule allows. After all, increasing by only a few kilometres per week in the early stages of training feels like nothing at all, and takes far longer to get to where you truly want to be with your training. Again, the more important steps are the hydration, the fuelling and re-fuelling, managing sleep and stress, and all the other necessary components to a proper recovery.

If you’re never allowing your body to recover, running day after day, and then increasing by 20% from the previous week, overtraining sounds like the only logical conclusion. But if you’re running something akin to one day on, one day off, there may be more room for wiggling – particularly if you’ve already established previous adaptations toward running high mileage weeks.

The close cousin to this rule is also that you should not significantly increase one aspect (volume, speed/intensity, elevation) at the same time as another. This also makes logical sense. Speed and intensity must be gradually introduced in a return to running post-injury. Strides serve as a wonderful opening integration of those fast-twitch muscle fibres, helping you skip the DOMS, and logically progress. But more generally, I think even this rule can have wiggle room.

If you were consistently hitting high vertical gain in previous training blocks, you might be able to progress from one stage to the next quicker than the 10% (or 30% elevation rule) allows. You might even be able to seamlessly increase vertical gain and volume in the same week, while integrating strides for the first time in your training. This would be increasing all three at once despite what the rulebook tells you not to do. Yet, runners have been capable of doing this throughout time.

The conclusions of this may have greater ramifications for elite athletes and those that have continuously put their body under duress in the past. But generally speaking, much of the science would suggest that even novice runners have more room to breathe within the 10% rule than injury preventionists may claim.

DOMS may occur only once or twice with a new experience (such as a long run after 13 weeks out injured), before subsiding the next time the action takes place. To only increase by a single kilometre the next week may not necessarily be the exact adaptation you need to continue your progress from one week to the next.

Here’s the kicker that most points me away from the 10% rule. No one in the history of time has been able to follow it. Of course, that’s a great exaggeration, and many elite Kenyan runners do the same monotonous training over and over with only slight adaptations. But if you look at any elite runner’s Strava, you’ll be hard-pressed to find ones that follow that 10% rule. Instead, you will see graphs full of ups and downs, weeks of no running followed by weeks of serious running, and massive increases from 60-70k a week, straight to 100-110k the next week.

Many of the runners at Black Canyon last week went from a tapered training week of 0km leading up to the race, to a single-event 100k. It’s significantly more than a 10% increase, but through months of training, they allowed their bodies to properly prepare for that moment.

Illustrating this phenomenon to a tee, take French runner Thibaut Baronian. Thibaut’s training has been fairly gradual this winter, but his cross-training has been incredibly sporadic. He went from 25km to 82km of Nordic skiing in February, then immediately back to 0km. In that week, he cycled for over 240km instead, despite doing 0 cycling in the month leading up. Athletes like Thibaut are able to tow the line between a 10% increase and a 240% increase, because their bodies have adapted to that kind of training stimulus over time.

Thibaut Baronian (@thibaut_baronian)

This isn’t to say that you should go out and cycle 240km tomorrow. Even if you’re David Goggins, you also shouldn’t race your first 100-miler on zero training. But your body might be ready to handle those extreme events more than a 10% incline would ever allow. Especially if you gave yourself enough time to recover before the next effort.

Much of the scientific literature suggests that a 20% increase may be more natural toward increasing volume safely. The body is seamlessly able to adapt to these changes, so long as those 20% increases are done once or twice, rather than every week. That is, it’s likely less than optimal to increase from 100km to 120km to 144km to 173km in the span of a month. But when running significantly less mileage and giving the body ample time to recovery, you may be able to surprise yourself. In fact, 20% really wouldn’t be all that much if you’re at the beginning stages of training, running low mileage, and running comfortably without any pain or doubt.

A 2014 study suggested that increases over 30% led to greater injury risk, but not a statistically significant difference when compared to less than 30%. More scientific literature in this area would help to draw greater conclusions, but depending on the stage of your training, your comfortability with your current training, and what you’ve done in the past, a 20% increase should not necessarily be ruled out.

With all this said, it’s worth noting that I will probably still follow the 10% rule. I’ve been an injury-prone runner throughout my life, and more than ever, I want to be careful this time. For what it’s worth, the 10% rule helps to curb overtraining, and ensures that the body is actually gaining the adaptations from the training imposed. This will be all the more imperative when I get back to running long across multiple days a week, with hard workouts and races interspersed into the mix. But for now, I’m cautiously listening to my body, running only a few days a week, and yes, increasing by more than 10% this week.

Thanks for reading & see you soon!

Strava Profile | Rhys Desmond


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