The old traditional rule says that you should never increase running volume more than 10% each week, particularly if you are a novice runner. Well a new study in the Journal of Strength and Conditioning Research used GPS devices to track running mileage increases in novice runners, to determine deleterious progression in running volume that caused injury, as well as find the threshold at which it was safe to increase weekly running volume without developing injury. The results, as you will see below, debunk the idea that a 10% increase is the ideal threshold, and, instead, most people can handle a greater increase in running volume, up to 25%. Also of note is that one’s BMI, or body composition seems to play a significant role in running volume and injury risk, and those with higher BMIs should use more caution.
The subjects included 60 healthy novice runners ages 18-65 from Denmark who had no injury and had not been running regularly. That’s a very small sample size, which is always important to factor into a study. It’s also important to note that these were novice runners, so these same rules may not apply for seasoned runners. This would also be very applicable to someone making a comeback from an injury or significant time off, even if that person has a history in running. But for those in season these same rules may not apply. I know, personally, in most cases I can jump back into a 20+ mile running week after a light week or week off and be just fine (but like I said, I would not do that when I’m coming off offseason and/or a significant break from running).
So the study used GPS watches (Garmin 110 Forerunners) to monitor running mileage progression, which is cool because in the past similar studies used questionnaires and more subjective means of data collection. The GPS eliminates any bias.
The runners were on a 10-week program and allowed to determine their own running volume. So what they were looking for was that percentage point that elicited a running-related injury. It’s always interesting to me when a study involves the onset of a new injury — in theory, researches shouldn’t set out with the goal of injuring subjects, so in this case it’s interesting to see the study design. The runners in this study were able to run as much as they wanted, so technically any injury that ensued was the fault of the runner, I suppose?
Runners were told what constituted a running-related injury and were instructed to report anything that fell within that range. Injury in this case was defined as a “musculoskeletal complaint of the lower extremity or back causing a restriction of running for at least 1 week.”
From there, they went on went their lives and did their running, uploading GPS data for researchers to view. The reserachers noted there was some user error involved in this process, but not enough to ruin the study. In total, the subjects ran more than 2,831 miles in 1,172 session over the 10-week time period.
Runners who sustained an injury increased running volume 31.6% on average, where as runners who did not get injured increased running volume about 22.1% on average. So the take home is that novice runners should not increase weekly running volume more than 30% on a weekly basis to avoid injury, but an increase of 20-25% appears to be safe. (To to this for yourself, fyi: In this study, “training progression was calculated in percentage based on the training volume covered in 1 week divided by the training volume covered in the week before, multiplied by 100”). So for example, you go from 15 to 25 miles, an increase of 10 miles. So that would be 10 divided by 15, x 100 = 66.67%.
Also, while I read the results I was thinking — and the study addresses this in the discussion — what about other variables in running beyond overall volume that could contribute to injury? Like intensity. Or the surface on which one runs. Or body weight. Or technique and form. After all, these were novice runners so I’m guessing they’re not all as smooth as your Mebs of the world.
The researchers did focus on one of those variables in particular: body composition. And they found that those who sustained a running injury had higher BMIs than those runners who didn’t get injured; with BMIs averaging 27.6 BMI in the injured vs. 24.8 BMI in non-injured. Thus, body composition and form is a huge factor in increasing run volume and developing a running-related injury. Again, this proves that a cookie-cutter plan can not be a “one-size-fits-all” sort of thing. When I take on a client, I take these things into consideration when formulating a program!
I am thankful that this study shows the old threshold of 10% is somewhat outdated and a little on the low/conservative side. Granted, there’s plenty of reason to still believe that 10% is the ideal progression for some runners, but it is not a set-in-stone rule as some articles and coaches may have you believe. Showing that novice runners can increase mileage up to 25% weekly without injury is promising. To me, it represents that a program should be based on the individual and his or her needs and abilities, and not based on generalities.
Keep in mind, though, it’s not like 25% is that much greater than 10% though! For example, this would be running 15 miles one week, then 18.75 miles the next — not that much more. Or, if going by time, that’s 2 hours one week then 2.5 hours the next.
So if you’re getting into running, or getting back to it after much time off just do the math to determine an ideal progression. You can do it based on miles or minutes — however you prefer to build your running program. Personally, when I am coaching someone new, I almost always use time, not miles, to write workouts. I think it’s safer especially because mileage times vary greatly depending on many factors — a 5-mile run can be 40 minutes one day or 60+ minutes another day, but 40 minutes is always 40 minutes.
Also, don’t discount other varibles that go into running and remaining injury free, namely intensity. Too high intensity and too much intensity in someone new is a recipe for disaster. Keep it moderate, i.e. a MAFF approach, if you’re just beginning, and slowly add intensity into workouts over time….