My left leg is a total slacker.
That's the conclusion I came to as I was walking Friday evening, testing the waters of my strained -- and slowly healing -- left arch.
Incidentally if you don't care about the foot mechanics of running, or about listening to me ramble about the minutiae of my gait, you're excused from class.
Personally, I like problem-solving when it leads to practical results (I don't like puzzles or games). I was walking up through the 'hood on a combo of dirt trails and streets to the
local hill, and was focusing on what my left foot was doing differently, because I'm convinced that bad mechanics is what caused the arch strain.

What I found was that my left leg is absolutely unfamiliar with leading and being the dominant leg. It's like it's been drafting in the shadow of my right leg all these years.
Bear in mind, I'm not talking about things you're likely to see if I'm walking down the street; I've managed to keep a fairly even gait in spite of it. I'm talking about a degree of difference that only becomes impactful after maybe 15-25 miles, when a small imbalance can add up to strain. I don't lurch sideways or anything like that.
When walking, my dominant right foot lands on the heel, rolls along the outside and then all five toes fold at the ball as the foot trails behind. It seems to have more control of my motion and be the resting base for my weight.

The left foot, on the other hand, lands on the heel, rolls along the outside, and then awkwardly moves over onto the ball, sort of skipping the outside toes. I don't feel a solid connection to the ground in the forefoot, or any sort of balanced weight-bearing, and I don't feel all five toes hinge as the leg trails behind. It's strangely uncoordinated in feel, like it's used to taking a shortcut because it doesn't have to do much.
Going forward, I have to be careful with this, because I don't want to make things worse by imposing new motions on body parts used to old habits.
However, I do want to try to even them out a bit. One thing I can do is to deny my right leg its role as the dominant leg in walking and running (by pretending I can't put as much weight on it), to see if I can develop more dominance and a normal footfall on the left side.

I tried and it's surprisingly difficult. I ran for a few stretches of 100-200 feet or so, and I think I can just concentrate on a flatter foot landing and it will sort itself out.
Oddly enough, walking seems to be the harder part. I have to concentrate to lead with my left leg. Nothing is automatic, I have to focus on everything and it seems totally foreign. Handling my weight and forward motion the way my right leg does is just not happening! It feels only slightly less pathetic than trying to write with my other hand.
An interesting part of all this is I've actually made walking into something new, decades after learning to walk. It's odd to feel like some part of walking is new after so many years.
But I'm going to keep at it, because I don't want to end up like
Zoolander, who can't turn left.