Wednesday, February 09, 2011

That P-Chain Thang

"Muscle strength and flexibility characteristics of people displaying excessive medial knee displacement"- Bell et al ', Archives of Physical Medicine and Rehabilitation '07.

My colleague Joe P. brought the above study to my attention in his blog this week. Hmmm...maybe it's true that the secret to life is in the ankles and not the posterior chain.

You know me, I totally think a gluteus maximus is a terrible thing to waste. But I'm not about to get caught with my head up my you-know-what when it comes thinking I can tell what muscle is firing where and when by observation alone. It just isn't that simple. We cannot and should not reduce human movement and performance to "activation" of particular muscles.

The term posterior chain is interesting. I have heard that it originated from one particular person about 10 years ago, but who knows if that is accurate. Maybe the concept came out of ACL prevention research? Oh, the girls are quad dominant--whatever that means. If you search Pub Med, the NSCA journal database or Sport Discus, you won't find any research with the key words posterior chain. The term does not denote a true physical system--similar to the term "core." It is simply the idea that certain muscles on your back side work together.

Here's what Wikipedia has to say:
The posterior chain is a group of muscles, tendons and ligaments on the posterior kinetic chain of the body. Examples of these muscles include the biceps femoris, gluteus maximus, erector spinae muscle group, trapezius, posterior deltoids, and so on.

The primary exercises for developing the posterior chain are the Olympic lifts, squat, good-mornings, deadlifts and hyperextension; the common denominator among these movements is an emphasis on hip extension.
For whatever reason, there's a tendency in this country at this time to think we have a dearth of hip extension strength (glutes and hams) and a wealth of knee extension strength (quads). That wasn't the case in 1998 when I first got into this profession. There was no big emphasis on hip extension. Somehow, somewhere, the emphasis changed from triple extension to emphasis on hip extension and this new thing emerged: the posterior chain. And what great timing it was, because suddenly we had become a nation of quad dominant, dysfunctional people, plagued by gluteal amnesia.

Welcome to 2011, where the key to athletic success and physical health is to strengthen the posterior chain. Training, athleticism and fitness have been reduced to one thing for many: strength or lack of strength at hip. Yes, I know about Vladamir Janda and his "Lower Crossed Syndrome" and his theories that many dysfunctional movement patterns are caused by a lack of hip extension strength. But as the study above points out, that might not always be the case. Causality can be tricky, especially when dealing with complex systems in the human body. Movement is more than meets the eye.

The kinetic chain includes the foot, ankle and knee. Without the musculature about the foot, ankle and knee, the hip is worthless. Strength, power and agility are about coordination and force production / attenuation via interaction with the ground. All ground-based movement is the result of a complex interaction of many systems, not just the hip. Instead of focusing on the hip down, I'd encourage you to think about force production from the ground up. Instead of focusing on strength, focus on skill, stiffness, reflexes, coordination and effective use of ground-reaction forces. Muscles are nothing without the nervous system and gravity.

By all means, squat til' ya drop. Live in The Big House. But keep the big picture in mind.

Hip extension should be a force to be reckoned with, but you are kidding yourself if you reduce athleticism, movement skill and power to 1) strength about 2) the hip. It's easy, tempting and even a little sexy to focus on such a prominent aspect of human physicality, right? And in the current environment you might even sound like you know what you are talking about if you can tell people you train the posterior chain because you do "x" type of squats, activating those glutes, hams and lats. But do you really know that? Got the research data to back it up or are you just parroting something you heard someone else say?

Don't let yourself get caught up in the hype terms like posterior chain or quad dominance. These are terms of convenience, not causality, when it comes to human movement. They are more style than substance. In reality, the most accurate descriptors of movement dysfunction or elite performance are much more complex. The remedy to a movement problem might be a simple manual or verbal cue, but the underlying processes and mechanics you are affecting are likely not so simple.


Howard Gray said...

Love hearing you so fired up Tracy! We need reminders like this one that evidence behind our practice is key

The Iron Maven said...

Just a little sassy today Howard! In all seriousness, yes, we need evidence, not bling or bravado.

Mike Bahn said...

Well said! Might have to print that one out (with credits)'s a gem.


Ben Moskowitz said...

So glute activation prior to a workout is baloney, while stretching/mobilizing so you can hit proper positions is worthwhile?

Chris said...

First of all, I just happen to have this study in my possession strangely enough...

I just wanted to make a few comments...

1. The subjects were not performing a regular squat - they were performing an overhead squat test per NASM guidelines. For the average person who does not Olympic lift or perform this movement regularly, it's pretty difficult.

2. They assessed all of these measures on one side only and on the dominant side. How can one conclude that there are not side-to-side asymmetries that may account in some way?

3. It is interesting that they measured hip abduction and hip external rotation ROM, but not hip adduction or hip internal rotation ROM. However, they measured these two values when assessing for strength. If there is an imbalance between hip internal/external rotation and there is some hip internal rotation of the femur that occurs during squatting, where does the additional necessary motion going to come from? Furthermore, the MKD folks also showed about a 20% reduction in ankle dorsiflexion in a knee-flexed position. So, again, where does that motion come from? You're locked up at the hips and locked up at the ankles - our buddy "the knee" sits right in the middle.

Since the MKD group did show greater hip external rotation, my guess is that they were lacking in Hip IR. The irony is that they even discussed the effects of hip IR and adduction issues in their introduction section and literature review. Why didn't they measure these things?

Just something to think about.