Miles-Equivalent Cross Training

I have been quite an avid runner during the past six years.  It's an old activity from my youth, interrupted for the most part by three decades (although in 1998 I did revive running for about a three-month period).  In 2007 I began to run short distances at a fast clip on my local YMCA's treadmill but began to tire of it, wanting to get to longer distances (and eventually a race or two...or more).  So I began to venture out on the road, increasing my distance and endurance to the point where I have run the marathon and now pretty much specialize in half-marathon races.  But unfortunately, lately my right foot has been bothering me and I've felt the need to lay off the running for a brief season.  This doesn't keep me from engaging in other activities, though, in an attempt to maintain my general level of fitness while recovering.  My problem is that it's hard to put numerical values on them that are comparable to the running mileage standard I've grown so accustomed to.  But I've come up with my own personal solution that should work for me (and not necessarily for you or anyone else).

My concept (which others have in all likelihood developed independently) is something I call "miles-equivalent cross-training", or MECT.  I  take different activities and assign them MECT "miles" based on the criteria I assign to them.  Here are a few:

--Bicycle riding-while keeping myself honest and riding at a brisk pace, I take my total riding time and multiple by a factor of .06 to get the MECT mileage.  For example, earlier this afternoon I biked for 63 minutes.  My MECT miles are thus 63 x .06 = 3.76 miles.  That seems about right for me.

--On the elliptical cross-trainer machine at my local gym, I also multiply total time times .06, while making sure I am putting out an honest effort.  The other day I worked out on it for 15 minutes.  That translates into 15 x .06 = .9 miles.

--I haven't used my gym's indoor swimming pool, but I already have a formula in place.  Each 25 m lap I cross I assign .1 MECT miles.  And it doesn't matter how I do it, whether by swimming any style, paddling, or even just walking across.

--I own a nifty little portable step exercise machine that puts out a strenuous workout.  I simply multiply minutes time .1.  Yesterday I was on it for 30 minutes, meaning I get credit for 3 miles.  And it felt like it, too!

--I have a push lawn mower, not one of those self-propelled types.  When I mow the front yard, I give myself 1 MECT mile.  The back yard is a lot larger, so I get 2 miles for doing that.

By assigning equivalence miles for alternate activities to running, I hope to help myself cope better with my temporary withdrawal from it.  But even upon recovery, I know I need to intersperse some of these other activities in between my running days so that future injuries are less likely to happen...