Are We Wasting Our Glutes By Sitting?
We all know that sitting is bad. We’ve been told by our physios, doctors and the internet. By this stage you probably have a decent idea of where your glutes are, and you’ve probably had someone tell you that you need to activate/strengthen them more.
Are we wasting our glutes due to their inactivity in our lives and why are they so relevant?
Why is being correctly stacked and activated in standing, walking, running or any other activity so important?
If we look at the evolutionary steps that have facilitated human posture, and gait we can find some answers to these questions: I really did get my geek on – so bear with me and feel free to ask any questions!
Evolution from Quadraped to Biped
The closets ancestors to the humans are the great apes; however one of the main differences that set us apart from them is our ability to stand and walk with two feet (bipedal gait).
In a study done by Goodall (1979) to observe the behavior of apes, it was noticed that one ape contracted poliomyelitis as an infant. This affected the function of one arm, this ape was unable to “knuckle walk.” This ape went onto developed a bipedal gait for locomotion (movement). The ape developed a lumbar lordosis to accommodate this (The great apes’ lumbar spine is usually kyphotic). The attachments of the gluteal muscles in the ape (which of course had not changed) prevented simultaneous extension of the lumbar spine and femur, and the inability to stabilise the pelvis in a one leg stance. In other words it could not walk as us humans do.
The evolution of the pelvic girdle reflects adaptations of bipedal gait:
Trendelenburg = Hip Drop
In apes, the gluteus medius and minimus work as femoral extensors (nerd way of saying hip extension); whereas in humans these muscles have migrated more forwards and sideways so that they work as hip abductors (moving the leg out to the side), preventing a trandelenburg gait.
In bipedal gait, we require good stability in a one leg stance to then swing the other leg forwards – the adaptation of these muscle attachments and function allow us to do this and set us apart from the apes.
Of course core stability also plays an important part in this as well!
Glutes and Core:
The surface area in the iliac fossa has increased in humans for attachment of the gluteus maximus (which compensates for the reduction in hip extensor power) and iliacus muscles (which has a significant role in maintaining erect posture). In humans, the glut max stabilises the pelvis and thorax to prevent them from pitching forwards when the hip flexors are used to swing the leg forwards while walking.
Hip Flexors:
We have developed more robust anterior iliac spines: ASIS where satorious attaches, and AIIS where rectus femoris attaches; both these muscles assist to flex the hip and swing the leg forwards with the aid of pectineus, tensor fascia latae, and the illiopsoas muscle groups. It is also interesting to note that rec. fem. is the only muscle that functions as a hip flexor in the quadrupeds.
Our acetabulum (which is the socket that holds our thigh bone/femur) is deeper and positioned more forwards and to the side, this then projects the femoral head more anteriorly. During gait, we then need to adduct our leg at heel strike to place the foot beneath the acetabulum.
The inominates (pictured above) have rotated 90 degrees on the sacral base (which is tilted forward further) to bring our head over our feet and facilitate standing on two feet. In turn we have developed a lumbar lordosis and a thoracic kyphosis. (Great apes have an almost immobile spine, and a much smaller erector spinae. Lovejoy (2007) feels that a mobile spine is crucial for upright walking).
Why are these changes necessarily?
Well, it makes us more efficient in an upright posture than the ape in Goodall’s study. Our body has evolved to give us the ability to stand, walk and run on two legs.
So in summary: our glute med and min work to stabilise our pelvis and trunk in a one leg stance as we stride. Our glute max gives us the ability to effectively keep our trunk upright while we stride. Our hip flexors are more powerful as we use a bigger muscle group to swing our leg forwards.
So, why do we spend so much time sitting?
Evolution has proved that we have changed to be more efficient on two feet.
Get out there and move!!
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References:
GOODALL, J., 1979. Life and death at Gombe. National Geographic 155 (5), 59
Lee, Diane, Linda-Joy Lee, and Andry Vleeming. The Pelvic Girdle. 1st ed. Edinburgh: Elsevier/Churchill Livingstone, 2011. Print.
LOVEJOY, C. “The Natural History Of Human Gait And Posturepart 1. Spine And Pelvis”. Gait & Posture 21.1 (2005): 95-112. Web.
Snell, C. A. R. D., and H. W. A. Donhuysen. “The Pelvis In The Bipedalism Of Primates”. American Journal of Physical Anthropology 28.3 (1968): 239-246. Web.
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