Ever read an article which makes you want to respond with, "well, duh...?"
I had one of those land in my e-mail late last week. Mind you, the article wasn't poorly-written or supported by sketchy claims, and there wasn't any sort of marketing thrust tied into it. It seems that researchers have learned that low-mileage training plans just might increase the chance of a running-related injury.
You can repeat along with me, if you like. Well, duh...
Inquiring minds like mine are always overjoyed when an article of this kind links to the original research. After reading one-too-many pieces written for national-level newspapers and magazines I've learned it's best to look at the original research studies. Sometimes there's more interesting "findings" which the magazine or newspaper writer conveniently decided to overlook.
I'll drop my stone right now, since I'm standing in the front yard of my own "glass house."
Rasmussen, et. al, (Rasmussen, C.H., Nielsen, R.O., Juul, M.S., Rasmussen, S. (Apr. 2013) Weekly Running Volume and Risk of Running‐Related Injuries Among Marathon Runners. International Journal of Sports Physical Therapy, Vol.8, Iss.2, p111-120, April.) surveyed participants of the Hans Christian Andersen Marathon in an effort to determine whether there was a correlation between self-reported weekly training distance and the self-reported incidence of a running-related injury during or before the event.
What the Danish researchers found was that a weekly training volume of less than 30 kilometers (about 18 miles) increased the chance of injury by 134% when compared to weekly training volumes between 30 and 60 kilometers (18-36 miles). Going beyond 60 kilometers per week saw no change in risk when compared to the 30-60km group. Less-experienced (or younger) runners showed a greater chance of injury; more-experienced runners and runners who were not participating in their first marathon also showed less chance of injury.
It's a given that running more not only encourages adaptations which make runners stronger and less-susceptible to injury, but also better at...well, running. The law of specificity tells us so. We can become strong by lifting weights and doing resistance training, we can enhance (or at least maintain) cardiovascular fitness by performing aerobic activities at a high level, but there are very few fitness activities which provide some semblance of crossover.
Low-mileage training might be good for the person who desires to dabble about with running, or the person who is extremely time-constrained. That's not saying that if a runner only has enough time to run 30 miles a week that they should not participate in long(er)-distance races, just that they might not find them as enjoyable as they might those distances which are shorter.