In Soviet Russia, the trail hits you!

There's a light at the end of the tunnel. Just go toward the light.

The tunnel in question is an unlit pedestrian underpass, just east of 128th and Holly, 2 miles along one of my regular running routes. There is a faint glow at the other end, showing me where I need to go. All that can be seen inside the tunnel is the reflection of that dim light on the water - or ice, as the case may be - that has accumulated on the floor of the passage.

So I always just run through, keeping an eye on the frozen sheen before me, expecting that one of these days I'm going to misstep and hit the concrete. Still, I was taken by surprise this cold and foggy morning when I hit the ground. And it wasn't the ice that got me, but a shopping cart.

Seriously.

Someone had left a shopping cart in the middle of the tunnel, hidden in the deep shadows, entirely invisible to eyes drawn to the light at the other end. So I ran right into it, knocked it down, and went over it and onto the concrete with a loud groan.

I picked myself up, righted the cart, and pushed it out of the tunnel as I took inventory of my several new aches and pains. I determined that there was no damage beyond a few minor scrapes and bruises. And I didn't want to blow my third week in a row of 35 running miles, so I continued on to finish up the ten-mile workout I'd been intending.

As I ran, I was tempted to wonder what kind of person would leave a damned shopping cart in the middle of a tunnel. But that line of questioning seemed pointless. I see them overturned in drainage ditches pretty often, presumably left by ne'er-do-wells who stole them from grocery store parking lots in the middle of the night to go careening down our suburban hills. It's very rare to see vagrants in these parts, so I can't imagine that they are being abandoned by the homeless as they upgrade to a new cart without so much wobble in the rear left wheel.

So instead of pursuing the question of who would do such a thing, I started wondering how much abuse my body can take. I'm 34 years old, which is not elderly by any stretch of the imagination, but I don't have much left of the resilience of youth in my frame. Last year's running season was brought to a premature end by knee pain. Recently, my right hip has been expressing complaints resulting from over-tight tendons or under-developed muscles. One of these days my luck will surely run out and I'll suffer a broken something-or-other when I take one of these spills while running or cycling.

But I've seen more bodies permanently broken from disuse than from being pushed too hard. From my viewpoint, it seems one retains physical faculties on a use-it-or-lose-it basis. So can I relent, taking it easier on my aging body in hopes of avoiding deterioration or damage that will manifest some day in the distant future? No, all I can do is keep going, try to use my body better and make it stronger. If I go fast enough, I'm pretty sure I'll be able to outrun old age.