This article was originally posted by Ryan at the original HillRunner.com Blogs.
Engine? Chassis? Are we talking about cars or runners?
A lot of coaches and experienced runners say things like the engine adapts faster than the chassis, make sure your engine doesn’t break down your chassis.
Obviously, this is an analogy to cars but what does it mean to the runner?
The engine is the power source. It’s your heart and lungs. Your heart and lungs adapt to training and their capacity increases fairly rapidly.
The chassis is the structure that delivers the power to the road. It’s your legs in short. The muscles, tendons, ligaments, bones and all the other structures that you use to apply force to the ground in order to move yourself. Your muscles adapt to training somewhat rapidly but not as rapidly as the heart and lungs. Tendons, ligaments and the other structures adapt much more slowly.
So what’s the point?
The point is many people get a few weeks into training and are feeling good. The breathing is relaxed. If they use a heart rate monitor, they see their heart rate going down. They figure they need to push more to keep the training up.
These people will often run into problems because their legs aren’t ready for the demands. Injuries creep up and suddenly the training cycle they just had a great start to is getting interrupted. It turns into a cycle of inconsistency.
So what to do instead? Pay more attention to your legs. Some feeling of heavy legs is normal and expected, especially in those early stages of training. Even a bit of soreness. However, if the soreness lasts for more than a few days or if it develops into a sharp pain, be smart about it. No matter how relaxed your breathing is or how low your heart rate is, it all doesn’t matter if you’re on the path to an injury. You’re only as strong as your weakest point and, early in your base training, that weakest point is usually in your legs, not your chest.
Treat your chassis well. If you don’t, your engine will break it down.