A tool to help avoid running injuries

Okay, so believing that I have grasped the basic mechanism and dynamic behind repetitive-use injuries that strike runners and others, and having resumed running several months ago after recovering from my stress fracture, I now face a mystery that it is most urgent for me to solve, and which I have therefore been highly motivated to try to crack (so to speak): 

just how much running can I get away with, without reinjuring myself??

So just to review, here's what we know:

1. When you run or work out, you stress your muscles, tendons, ligaments, and bones
2. When you stress your tissues, they get injured in microscopic, sub-symptomatic ways
3. In repairing those injuries, your body makes those tissues stronger
4. Bones and ligaments can take many weeks to repair
5. If the stress you place upon your tissues outpaces your healing, you get an injury

There are no doubt other, more complicated things going on as well in an injury; for example some believe that fatigue in your muscles from a long run makes them lose their elasticity and function as a spring, which when strong protects your bones from shock.  Running form must be important; I continue to run barefoot in attempt to optimize that.  But let's put aside such complexities for the sake of clarity.

One of the things that I have done since I first began running & triathlons 3 years ago is keep meticulous workout logs.  So I have records of every run I have done, as well as records of the five times in that period when I felt compelled to take a break from running due to pain.  So the question is, how did my mileage correlate with those injuries? 

To look at that, I first created a graph of all my runs since April 2005, and marked on it the dates on which I got injured (red splotches).  The result looks like this (click images to view fullsize):

  

Well that's kind of interesting, clearly I got injured as I did more longer runs, but the injuries were still somewhat unpredictable.  And just how much running, and how much increase in running, is too much?

In an effort to shed more light on what happened, I got the idea to do a different analysis: I calculated, for each day since April 2005, how many miles I had run in the previous x days, where x was 30, 45, 60, 90, and 120 days. 

So for example, on August 16, 2007, the day I first felt my stress fracture, I had run 45 miles in the previous 30 days, and 122 miles in the previous 120 days.  How did that compare to the dates of my previous (less serious) injuries, and to other, normal days?  Did any of those date-ranges predict my injuries? 

I piled all those graphs on top of each other, and superimposed them over the above "spike" graph of my actual runs, and this was the result:

Looking at all the graphs, it seems to be the 60-day (blue) and 90-day (yellow) graphics that seems to correspond most closely to my injuries -- when that line spikes, I tended to get injured.  (The exception was the runup to my first marathon in October 2006 -- but I will note that, although I haven't marked the period as containing any injuries, in the months between that marathon and my second the following March, I consistently felt a lot of the bad kinds of soreness following most of my long runs). 

I therefore settled on the following graphic as best representing my ongoing tissue-injury state.  The Rolling Cumulative Run Record (which somebody has no doubt invented already but which until I hear otherwise I am going to name my "RCRR") is here shown as a rolling average of miles run per day, and the individual run distances (black spikes) are scaled such that 26.2 = 1.  That gives a nice clean visual demonstration of my running state:

One of the striking things about this chart is just how steeply the yellow line rises, even when I was just doing steady, short runs, thinking I was being super cautious and taking it super easy -- whether in the spring of 2005 when I first started, or in recent months as I have restarted running. 

Here are the questions that all this leaves in my mind:

Just how gradual a slope is safe?  Of course this naturally varies by runner -- doctors say healing times for bone fractures vary greatly by individual, and it must be no different with other tissues.  But I wonder if research would uncover a general guideline for runners. (Of course the visual steepness depends on the way you scale your graph, so it's hard to know how to interpret it.)

Is a plateau safe?  Is the right thing to do to reach a plateau, where your 90-day line is basically flat? If you can get there and stay for a while without injury, is that the way to avoid injury?  Just how many injuries are a result of a too-steep a line of increase?  I bet it's the vast majority.  If you run the same amount per week/30/60/90/120 period for years, with no increase and no injury, how likely are you to suddenly get injured? If you run the same number of miles each day your line would be perfectly flat; if you vary by day but run the same number each week, it would be somewhat wavier. Here for example is the graph of a person running one mile each Monday, 2 every Tuesdays, etc., up to 7 on Sundays:

The longer the period of your consistent run totals (ie you repeat the cycle every 2 weeks, every month, etc), the more wavy your RCRR line will be.

What is the best way to distribute one's miles?  Just how wavy a RCRR line can one have?  What is the relationship, injury-wise, between cumulative run totals and the lengths of individual runs?  In other words, to avoid injury are you better off doing the same run every day, or periodic, longer runs with long rests for healing in between?  For example, let's say I average one mile per day; is it better to run one mile per day, or 7 miles once a week?  What is the best balance between those extremes?  Clearly if you want to do a marathon, it won't do to average 26.2 miles per month by running 0.845 miles every day.  But there are also people who can run numerous marathons a year without injury -- and clearly they can't run a marathon every day.  So what is the best "rhythm" for incorporating long runs into one's overall mileage?   I think the standard advice is to go easy every 4th week or so; I wonder how accurate that is.

In my own injuries, only one (my stress fracture) was directly the result of a long run.  The other points I have marked, such as after my second marathon, were merely points where rising soreness prompted me to make the decision to take a break, following long periods of increasing but not catastrophic soreness.  But, they were periods where I was doing long runs interspersed with long breaks of only a few short runs.  I figured I was giving my body a good chance to heal between long runs by doing little volume in between.  Now I am experimenting with more frequent short runs. 

But, the biggest question in my mind as I try to become a healthy consistent runner is: Am I once again headed for an injury? 

I have been increasing my run so slowly -- from my first half-mile run at the beginning of March, I increased to no more than 5-mile runs by the end of July, 5 months later.  Since then I have done a 7-miler and a 10-miler, but my mileage remains extremely low and I am being so cautious.  Yet look at my yellow RCRR line, on the right edge of the above graph.  Its slope is definitely more gradual than those leading up to past injuries -- but still appears to be rising alarmingly.  I will certainly keep monitoring both versions of the above charts.  Time will tell.

FINALLY, for anyone that would like to track similar data for their own runs, here is a blank version of my spreadsheet for your logging convenience. (Also on there is form I use to log all my triathlon training.) Good luck! 

Download RCRR run injury prevention tool.xls

Comments

[sat ganesha]

Thanks for the RCRR tool as I am trying to prevent my often reoccurring "planterfacious" and my goggle search got your blog site. I will see how it works for me.

As input...my goal is to reach a "maximum" miles per week injury free and maintain that...while varying the intensity. So perhaps the third variable would be "intensity".

I heard as generic rule of thumb not more then 10% increases per week for total miles.

[Jay]

Sat - good luck with your plantar's and I hope my own experiences & analysis can be of some help. One thing my analysis suggests is that even the 10%-per-week rule may be way too much, especially once the distances start getting longer. Compounded, that would lead to a very steep line of increase.

- Jay