What the Strength and Conditioning Textbook Never Taught You: The World Isn’t All Concentric
Written on June 29, 2012 at 8:54 am, by Eric Cressey
As a continuation of this week’s series on things you didn’t learn from a textbook, today I’ll be talking about how we’ve misunderstood muscle actions. As we go through anatomy and kinesiology in the typical exercise science degree, we memorize muscle actions.
The quadriceps extend the knee. The biceps flex the elbow. The teres minor and infraspinatus externally rotate the humerus. You get the point.
The point that many folks don’t get is that this is simply a practice of memorizing concentric muscle actions, and the truth is that this is really only one-third of the picture when it comes to how we move. You see, these muscles are also acting isometrically and eccentrically; sometimes the primary goal is not to shorten, but preserve muscle length, or prevent uncontrolled lengthening. This is a crucial understanding for one to acquire, as poor isometric and eccentric control are the culprits in an overwhelming majority of non-contact athletic injuries.
Our shoulder barks at us because our scapular stabilizers and rotator cuff don’t function correctly to prevent, slow, or limit inappropriate movement. An ACL goes because glutes and hamstrings couldn’t control unrestrained knee hyperextension and hip adduction and internal rotation.
To that end, while you might memorize a muscle’s concentric action first, it’s important to infer from that understanding that it has more implications above and below the joint it crosses. At the subtalar joint, pronation kicks off tibial and femoral internal rotation each time we land from taking a step. The gluteus maximus – as a hip external rotator, abductor, and extensor – plays a crucial role in decelerating this internal rotation and the accompanying hip flexion. In other words, your butt is an anti-pronator! Just watch what happens on the way down in a bowler squat and you’ll appreciate pick up what I’m putting down:
When you start looking at all movement like this, it will have a powerful influence on your ability to help people move more efficiently. With that in mind, I’d encourage you to look over the last strength and conditioning program you wrote and try to consider how the exercises you programmed help to prevent or control unrestrained movement, rather than creating movement. My prediction is that you’ll notice several exercises in there that you might not have included if you’d thought about this beforehand.