A Window into the Glutes: Anatomy lesson for the day.

A rather literal statement for a rather literal picture. Taken from the Human Body Exhibit at the Denver Museum of Science, this picture offers us a glimpse into, or in this case through, one of our favorite muscle groups. This group that we see here, is probably our second favorite group. They are often called the “deep six” and are the deep hip external rotators. If you count, you will notice there are only five….one remains unseen the obturator internus. More on that later.

See the linear white lines on the right of the window? That’ s the two portions of the sciatic nerve. Notice how it runs under the muscle at the top and over the others? The muscle it runs under is the famous piriformis. When this muscle gets tight, it can impinge the sciatic nerve, causing pain down the leg (known as sciatica). This represents one of many causes of pain radiating down the leg.

The next muscle south is the gemelli superior, then the obturator externus, gemelli inferior, and quadratus femoris. The sixth of the deep six is the obturator internus, which runs from the inside of the pelvis on the obtrobturator foramen (those huge “eyes” you see in an x ray when looking at a pelvis from the front) to a similar place on the femur.

A few observations you should make.

• when someone chews your butt off, or chews you a new one, this picture gives it a whole new meaning

• the sciatic nerve runs under the piriformis

• The top (superior) five muscles have a tendonous insertion to the femur that you can see as a whitish area on the left

• the last (or most inferior muscle) has a muscular insertion to the femur (which is a reddish area on the left)

• the positioning of these muscles allows them to be external rotators of the femur when the foot is in the air

• when the foot is planted, they become external rotators of the pelvis or can act to slow internal rotation of the femur during stance phase

• as you proceed caudally, the muscles become stronger adductors of the thigh

We will see this post as a reference for some future posts on this most fascinating muscle groups. Until then, study up!

The Gait Guys. Uber Foot Geeks. Join us in our mission to educate the world on the importance of understanding human motion and its impact on translating us forward in the gravitational plane.

all material copyright 2013 The Gait Guys/ The Homunculus Group. All rights reserved

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Great Gait: You don’t see this that often

Great gait brought to our attention by one our readers; one his questions was how he had such great “kick back” traveling at the speed he was traveling at. 

 

Here is an efficient gait:  note he mid foot strikes (you may need to watch it a few times to see it) close to under body and does not over stride; he has great hip extension, and a forward lean at the ankles; even arm swing (note elbows do not go forward of and wrists do not go behind body). It all adds up!

So what causes such great hip extension? Largely 2 factors: forward momentum and glute (all 3; max, med and min) activation. From the last post and EMG studies, we know the glute max contracts at initial contact (foot stance) through loading response (beginning of mid support) and then again at toe off to give a last “burst”; the gluteus medius and minimus contract during most of stance phase. initially to initiate internal rotation of the femur (a requisite for hip extension);  the former to keep the pelvis level and assist in extension and external rotation during the last half of stance phase to assist in supination and creating a rigid lever to push off of. This is, of course, assisted by the opposite leg in swing phase.

Forward lean and momentum move the axis of rotation of the hip behind the center of gravity, assisting the glute max to extend and prepare the lower limb for the bust at push off. The stance limb, now in external rotation, makes it easier to access the sacral (especially) and iliac fibers of the glute max and the posterior fibers of the gluteus medius.

What a orchestration of biomechanics resulting here, in a symphony of beautiful movement.

The Gait Guys. Bringing you great gait, when available…..