I've been thinking a lot about the training season, injuries and the conversations I have with my running buddies about training. My thoughts on the subject are as follows and this is essentially the lecture I would give my clients when I was a personal trainer.
Running is a repetitive motion. Think about your image of a 19th century factory, or a modern cell phone factory for that matter, lots of people doing the same thing over and over until they get over-use injuries, carpal tunnel, broken down joints, or just get injured because they become so robotized that they stop paying attention and forget not to put their hand in the steel press.
The idea behind cross-training in a running program is to add stress to the muscles, tendons, ligaments, skeletal system etc. that you aren’t getting by just running. Your body is amazingly efficient at streamlining activity, reducing the amount of energy expended to complete a repetitive motion and building infrastructure to support it that basically restricts any motions your aren’t using. That is to say, if all you do is run in a straight line your body will tighten up to support that and become brittle to any other movements. Like a factory worker, your body will become very prone to injury the second you move in an unexpected direction.
The solutions to this are simple: cross-train, trail run. Trail running is less repetitive because you have to adapt to an unstable environment. When I’ve been road running (meep meep) for a while and I get out on a trail, I get pops and cracks in my knees for a bit but I start to loosen up quickly. Step on a root and almost sprain your ankle once or twice and you’ll quickly develop laser focus. More than that the terrain builds supporting and core musculature because you have to be more nimble in an unpredictable environment, your tendons and ligaments have to be loose enough to keep strains from happening when they must unexpectedly stretch, but tight enough to prevent over extension injuries. All of this is really good news for you.
The example I like to give is this: professional/competitive road cyclists are well known for having very low bone density and high risk for osteoporosis. How can this be, they’re athletes? The answer is Wolffe’s Law. “Bonein a healthy person or animal will adapt to the loads it is placed under. If loading on a particular bone increases, the bone willremodel itself over time to become stronger to resist that sort of loading.” I add to this that the same is true of muscle, ligament and tendon (it’s why weight lifting makes muscles bigger). The same is true in reverse as your body will reduce infrastructure on any structure that isn’t under load. Cycling is a very low impact sport, unlike running where there is always impact with the ground. Their bodies demineralize bones just like astronauts'.
Workers at the Maker’s Mark distillery are required to switch jobs every 30min to keep them alert and injury free. If all you do is run in a straight line you’re setting yourself up for an overuse failure. Cross training adds additional stresses and helps your body stay supple and trail running does the same.