For some the jury is still not out on whether one should or should not engage the gluteus maximus muscle when performing back bending yoga postures.
Firstly, let’s have a close look at the functional anatomy of this muscle. Gluteus maximus, commonly known as glute max, is the superficial ‘rump’ muscle of our buttocks. Its prominent, characteristic shape and large size correlate to its powerful role of maintaining our trunk in an upright position. Additionally, gluteus maximus plays an essential role in gait, i.e. walking. When we walk it is glute max that provides the power to propel us forward as well as taking the leg back ready for the next stride. Its main action is extension or hyperextension of the hip joint, which is the action used in back bending. Additionally, glute max externally rotates the thighbone or femur.
The only other major muscle that performs hip extension is the hamstrings muscle group. The hamstrings are bi-articulate, which means they cross and therefore act upon two joints. The other joint that the hamstrings act upon is the knee joint where they perform knee flexion. This means that, especially when the knees are bent and the hamstrings are already shortened, they become less effective at hip extension. On the other hand, gluteus maximus being a single-joint muscle is very effective at hip extension. It is the major extensor muscle of the hip joint.
This begs the question, if we do not use the gluteus maximus muscle to extend our hips in back bends which muscle(s) will we use?
There are only two choices. One is that we can use the hamstrings group. As explained, the hamstrings are less effective at hip extension in any back bend where our knees are bent (Dhanurasana, Ustrasana, etc.). The other choice is to use the spinal extensor muscles. These include the erector spinae muscle and the deeper quadratus lumborum (QL) muscle in the low back. Note that these muscles cannot contribute to hip extension, which is required for back bends, as their function is extension of the lumbar spine or low back. Obviously, lumbar spine extension happens whilst performing a back bend but over activity of the lumbar extensor muscles causes excessive movement and compression of the vertebral facet joints, which join one vertebra to the next, and can strain the low back.
Excessive movement and compressive forces in the low back in back bends often comes from an incorrect firing pattern of the extensor muscles. In ‘Rehabilitation of the Spine’ Craig Liebenson describes the correct firing pattern in hip extension. The firing pattern necessary to avoid the pelvis tilting forward which deepens the lordotic curve in the low back is when glute max fires first.
This is then followed by the contraction of the hamstrings and lumbar extensor muscles. Problems arise when glute max contraction is late, decreased or absent. By engaging glute max first, the pelvis is anchored to the thighs posteriorly (in the back). Most importantly, this keeps the primary fulcrum or axis of the back bend at the hip joint instead of in the low back. This prevents hypermobility and especially end-range loading of the facet joints of the lumbar spine.
Dr Vladimir Janda, known as the ‘Master of Rehabilitation’, noted that certain muscles tend to be inhibited (have less tone), while others tend to be hyperactive or facilitated. An inhibited muscle is different to a weak muscle in that inherently it may be strong but other factors such as trauma, stress or overuse may prevent it from functioning optimally. Inhibition of a muscle implies a deficit in neurological input.
Glute max is one of the muscles that tend to be inhibited, whereas the erector spinae, QL and the hamstring muscles all tend towards hyperactivity. If glute max is inhibited it needs therapy such as post-isometric relaxation, PNF (proprioceptive neuromuscular facilitation) diagonals or joint mobilisation or manipulation as well as inhibition of the hip flexors. Glute max weakness requires a focused exercise program to strengthen it.
A common pattern is inhibited and/or weak glute max muscles with overactive hip flexors. Muscles work in pairs with one opposing the action of the other. This means that engaging the hip extensor muscles causes the hip flexor muscles (those in the front of the hip joint) to
release in a neurological process known as reciprocal inhibition. The hip flexors are the very muscles we are trying to stretch and lengthen to improve our back bends. As the hip flexors also tend toward hyperactivity this helps to ‘switch off’ these already over used muscles. Engaging glute max in back bends enables us to achieve this more effectively.
The main concern that has steered the yoga community away from using glute max in back bends is the fact that excessive external rotation of the thighs can jam the sacrum between the two halves of the pelvis.
An inability of the sacrum to float freely between the pelvic halves at the sacroiliac joints is a common source of sacral, hip and low back pain. However, it is not only activation of glute max that is the cause of this adverse effect but more specifically over activation of the deeper piriformis muscle. The lower fibres of glute max do attach to the outer rim of the sacrum but the piriformis has an even greater lever on the sacrum. It originates on the front (anterior) aspect of the sacrum (S1 – S4) and extends horizontally across the buttocks to insert on the greater trochanter of the thighbone (the most lateral boney protrusion on the outside of your hip). The action of the piriformis is external rotation of the thigh but it is its tendency toward hyperactivity that make it prone to spasm which is the cause of sacral jamming.
Excessive external rotation of the thighs is easily counter-acted by engaging the internal hip rotator muscles which then keep the feet straight in back bends. The muscles that perform medial or internal rotation are the hip abductors: gluteus medius, gluteus minimus and tensor fascia latae and the hip adductors: the anterior portion of adductor magnus, gracilis and pectinius. These muscles are most easily activated by grounding the medial side of the feet in back bends, i.e. the base of the great toes and the inside edge of the heels. This action keeps the piriformis muscle out of the picture and tempers the external rotation component of glute max’s activity. This prevents sacral jamming whilst still enabling us to effectively and efficiently extend the pelvis.
It is here that a teacher’s choice of terminology can help students to refine their performance of any back bend. For example, instructing students to ‘squeeze’ or ‘clench’ their buttocks can induce indiscriminate activation of all the buttock muscles including the deep external rotators. Engaging glute max does not mean to negate any of the other important factors of back bending. This includes engaging the adductor muscles of the inner thigh to induce an upward vector along the spine, keeping the knees tracking over the ankles and nutating (forward tilting) the sacrum to unravel and lengthen the spine.
Of course not all back bends are the same and in those where gravity does a lot of the extension for you (eg, Ustrasana and drop backs), it may appear that using your gluteus maximus is not as important. However, again if the glute max does not contribute to hip extension the axis of backward rotation will move up into the lumbar spine. When we extend backward from standing the hip flexor muscles, especially iliopsoas, must contract eccentrically (lengthening as it contracts) to enable us to control the movement against gravity. If glute max does not share some of the workload the hip flexor muscles must then take the entire weight of the torso. Additionally, glute max provides 70% of the stability of your pelvis. Co-contraction of glute max with the eccentric contraction of the hip flexors provides us with important lumbopelvic stability.
Gray Cook the founder of ‘Functional Movement Systems’ describes the tendencies of different joints toward mobility or stability. The hip joint is inherently stable and thereby tends toward stiffness. At the other end of the spectrum, the sacrum and lumbar spine are inherently mobile and tend toward instability. The strong action of glute max helps to combat this stiffness by specifically targeting the hip flexor muscles whilst providing stability for the low back and sacrum.
There is one point in a back bend where we could choose to disengage our glute max and that is once full extension of the pelvis has been reached. Here is it is possible for many students to relax their glute max and still maintain their back arch. This will depend to some degree on your flexibility, muscle mass and the inherent resistance of your muscle tone. If you are very flexible in a back bend you may not need to engage glute max to achieve a deep back bend but you do need to note where the fulcrum of the movement is: in your low back or at your pelvis.
The choice many students make to not use their glute max in back bends is usually to avoid possible harm. Unfortunately, this perpetuates the tendency for weak and/or inhibited glutes and hyperactive hip flexors. Gait is our most frequent functional movement pattern. Without glute max to initiate the propulsion and produce extension of the hip joint this movement loses its integrity. In our analytical attempts toward precision and correct alignment in complex postures we risk losing the natural integrated movement of performing these postures. The natural ‘gait’ of back bending requires glute max to stabilise the pelvis, to provide a safe, secure pivot point for extension, to protect the low back and to enable us to safely enjoy the great benefits of arching backward.
Burton Lee, Kiesel Kyle, Rose Greg & Bryant Milo F. Movement: Functional Movement – Expanding on the Joint-by-Joint Approach. Available from: http://graycookmovement.com [8 July, 2013]
Janda V 1995. Evaluation of muscle imbalances. In: Liebenson Craig, Rehabilitation of the Spine: a Practitioner’s Manual. Williams and Wilkins. Baltimore.
Liebenson, Craig 1995. Rehabilitation of the Spine: a Practitioner’s Manual. Williams and Wilkins. Baltimore.
Marieb Elaine N 2004. Human Anatomy & Physiology. Pearson Benjamin Cummings. San Francisco.
Muscle images taken from visible body 3D Muscle Premium, www.visiblebody.com