That long-distance running causes injuries is certainly not startling news to anyone who engages in this activity. Very few of us escape indefinitely the results of miles and miles of pounding the pavement over the years. The available statistics would seem to confirm this.
For example, the results of a 1984 study of 4,358 male runners entered in a 16Km (10 mile) race in Switzerland revealed that 46% had suffered a running injury during the previous year. Of these, half were forced to either reduce or interrupt completely their training. One out of seven sought medical treatment, and 1 out of 40 missed work due to the injury.
Other studies show similar results, ranging from 30% to 60% of runners sustaining an injury each year. While the authors of these investigations propose a wide variety of possible causes for these injuries, including improper footwear, biomechanical abnormalities, running surface, etc., none have been able to show a direct, convincing relationship between these factors and incidence of injury. The one exception is the strong correlation between weekly mileage and injury occurence, sometimes referred to as the “dose-response” relationship. (Now you know why they call running an “addiction”!)
Because of this statistical consistency, “self-induced training error” is generally listed as the number-one cause of running injuries. Most experts believe about 60% of all injuries fall into this category, with the remaining 40% blamed on the multitude of factors mentioned above. Most of you have probably heard this term before, but I imagine many of you might ask, What exactly does “training error” mean? How will I know it when I see it? And, can I avoid it so I don’t have to see it? As you might suspect, the answers to these questions defy simplicity. But let’s give it a try anyway.
“Training error” to most experts is synonomous with “a sudden increase in running mileage.” The conventional wisdom says you shouldn’t increase your mileage by more than 10% per week or you will be courting injury. The theory behind this thinking is that the pertinent structures of the body most involved with running (muscles, tendons, joints) have not had sufficient time to adapt to the additional stress and thus will “break down.” Moreover, this would apply not just to increased mileage but for increased effort (i.e., speed) as well. Is this true? In theory, yes. In reality, sort of.
Body structures do adapt to stress by increasing mass and/or strength of the tissue. This is the “training effect,” the way we become stronger and fitter. If we don’t increase the load, we don’t improve. It seems logical to assume that if we increase that load by too much we will naturally have a problem, but just what is meant by “too much?”
Obviously, going from a steady schedule of 30 miles per week (mpw) for six months to 40 mpw for several weeks is risky, but this is not the only definition of “too much.” In fact, I think most runners instinctively know this and are not that foolish. The more common example of “too much” involves what I would term “bingeing-without-backoff.” Here’s what I mean: It may not necessarily be inevitable that you will injure yourself if you occasionally increase your mileage or speed more than 10%, provided you rest sufficiently following this to allow the body adequate time to adapt to this stress. For example, I believe you can go from a regular diet of 30 mpw to one week of 50 miles and then to a week of 20 before getting back to 30. In fact, I think this can be beneficial and safe. But, if you return to your regular 30 mpw after the week of 50, this is where you can find trouble.
Almost without exception, runners I have seen with what I consider “training-error” injuries report that latter scenario. I rarely encounter someone who is injured after the 50 mile week, but rather 2-3 weeks later after more 30 mile weeks. This “delayed reaction” is typical and most likely due to a progressive weakening, eventually to the point of failure, of the body’s tissues following a brief overload without subsequent rest and recovery before resuming the regular training schedule.
So how will you know a training-error injury if you see it? Perhaps if it fits the pattern I have described. How can you avoid it? Plan ahead. Throw in that “big week” once in a while, but schedule a rest week or two following it before you pick up where you left off.
As you might suspect, training errors are not isolated from other causes of running injuries. They are interrelated with biomechanical abnormalities in particular and it is this huge area we will begin to tackle next month by discussing “Foot Orthotics – Are They THE Answer?”