Anatomy class often leaves us with many questions. Sometimes we are lucky enough to know what those questions are, but quite often, we are unaware of the information overload we receive and its many implications.
For me, one of those unasked questions was the apparently simple – ‘why are some muscles different shapes?’ I took it for granted that some muscles just had different arrangements, but there are reasons for the various patterns that become clear on appreciation of the wider anatomical structures. Thankfully, sometime in 1999, I came across an article by my eventual mentor, Tom Myers, which laid out the logic for the very complex arrangement of muscle around the hip joint and clarified many of the body’s sophisticated strategies to facilitate our complex movement.
The hip is one of the main areas that has allowed us to walk upright. Compare the skeletons in figure one and look closely you will see the different alignment of the ilia between the primate and human. The muscle tissue on the posterior aspect of the primate ilia can easily create extension but would struggle to control the adduction necessary for single leg stance (see figure 2). The full 3-dimensional movement of our pelvis requires a circumferential arrangement of tissue to control the various forces passing through the area. These forces include ground reaction force coming up the anterior limb (the right limb in figure 2), and momentum of the swing leg (which will be the left leg in figure 2 which is about to be released at toe-off).
Being a ball and socket joint, the hip can obviously move through all three dimensions and each of those movements has to be controlled by appropriately placed muscle tissue. Presumably, the primate hip joint will allow a similar range but it has a primarily backward facing ilia. Therefore the primate doesn’t have laterally facing ‘abductors’ which are necessary to control the adduction we see in the human right hip in figure 2, reducing frontal plane support and control.For single leg balance (required for walking but exemplified in ballet) the full range of motion has to be decelerated by tissue arranged around the full circumference of the joint. The human body has created a wonderful way of managing those forces by developing a sequence of muscles arranged in a series of fans.
The simplest and most familiar is probably the hip abductors (see fig. 3) that, in walking, will actually control adduction rather than create abduction. Because of their triangular arrangement, they can decelerate adduction through the range of flexion (right hip in fig.2) to hip extension (left hip in fig. 2).
This triangular arrangement of muscle is common across ball and socket joints. The joint can be active through a wide range of movement and therefore requires a wide range of control. This is in contrast to the more linear muscles that cross hinge type joints. With a much smaller range of motion, hinge joints do not need fan-shaped tissues as their greater potential range would be wasted on the limited joint ability.
Fusiform (long parallel fibre) and pennate (feather-type) therefore tend to cross joints with limited axis of motion. Deltoid muscles, and fan-like arrangements cross ball and socket joints.
We see this clearly in the case of the hip joint (see fig. 4) where the muscles attaching to the greater trochanter can control abduction, flexion, extension, internal and external rotation. The inside of the joint is controlled by a similar arrangement (see fig. 5), giving us complete 360-degree coverage of required range of control.
The Anatomy Trains school has developed a range of workshops designed to clarify myofascial and functional relationships. They have been developed by Tom Myers and James Earls, authors of ‘Anatomy Trains’, ‘Fascial Release for Structural Balance’, ‘Born to Walk’ and numerous articles. During the ‘FANS OF THE HIP’ workshop we will explore these relationships further, clarifying the rest of the ‘fans’, their roles, their implications in dysfunction and how to ease them with manual techniques and educate them with functional movement exercises. I look forward to seeing you there.
Images from Born to Walk: Myofascial Efficiency and the Body in Movement James Earls North Atlantic Books; 1st edition (July 22, 2014)
About James Earls
James Earls is a writer, lecturer and bodyworker specialising in Myofascial Release and Structural Integration.
Increasing the understanding and practice of manual therapy has been a passion of James' since he first started practicing bodywork over 20 years ago. Throughout his career James has travelled widely to learn from the best educators in his field, including Thomas Myers, developer of the Anatomy Trains concept. James and Tom founded Kinesis UK, which co-ordinates Anatomy Trains and Kinesis Myofascial Integration training throughout Europe, and together they authored 'Fascial Release for Structural Balance,' the definitive guide to the assessment and manipulation of fascial patterns.