In order to achieve good alignment and correct movement mechanics, the body must have the tools to do so; a well-balanced musculoskeletal system is the first step in this quest. Strength is obviously an important aspect of posture, yet other elements, such as habitual muscle activation patterns, genetics, and flexibility are also key components. In many instances, a lack of flexibility inhibits ideal alignment and recruitment of the correct muscles. Hypermobility, on the other hand, although not restrictive by nature, demands a great deal of body awareness and muscular control to maintain good alignment. In Pilates we strive to develop strong, flexible muscles that are effective in their function and adaptability.
Certain muscles play a crucial role in providing a stable and pliable core, without which good alignment and efficient function are not possible. These are the deep muscles of the pelvis and trunk. The superficial muscles are sometimes overdeveloped and overemphasized in comparison to the deep muscles, often at the expense of a strong, solid core. Being large does not necessarily translate into being functional. I regard muscle bulk that is not functional as extra baggage to carry around; ultimately, it can burden the body. As with a tree, the deeper layers, not the bark, provide the support for it to stand upright and the flexibility to bend with the wind.
The back extensors and abdominal muscles are key in providing the form and function of the trunk. They share a symbiotic relationship and there should be constant interplay between them. Both the abdominals and back extensors are made up of layers of muscle, and it is the deepest layers that are most prominent in providing stabilization and support to the spine. The abdominal group is made up of the rectus abdominis, external oblique, internal oblique, and transversus abdominis (figure 2.4). In back, the large superficial group (erector spinae) runs longitudinally along the spine, while the deep posterior spinal group (which includes the multifidus), the intervertebral muscles that connect between the vertebrae of the spine, lie deeper (figure 2.5). The back also serves as the attachment for many dual-purpose muscles, such as those connecting to the neck and head, the upper limbs and the pelvis. Within these two major muscle groups, the abdominals and back extensors, two muscles have been identified as having a particularly profound effect on stabilization and, in turn, function: the transversus abdominis (TA) and the multifidus.
The abdominals and back muscles, together with the diaphragm and the pelvic floor, create a cylinder of muscular support in the center of the body. I call this the internal support system (ISS). It is congruent with the powerhouse in Pilates, or the core in other forms of training. It is gratifying that scientific research is now substantiating much of what Joseph Pilates advocated so many years ago with regard to the importance of a strong, powerful, and functional core. During the practice of Pilates, you are encouraged to recruit the muscles of the ISS throughout. Movement is possible without activating the ISS; however, internal support, protection of the spine, and efficient function are likely to be diminished.
Another component that is important to consider in any discussion relating to the pelvis and the spine is the psoas. There are two psoas muscles, psoas minor and psoas major. Psoas major combines with the iliacus to form the iliopsoas (figure 2.6). Besides being powerful hip flexors, these muscles are believed to substantially influence spinal stabilization and alignment. Since the psoas is close to the axis of movement when performing flexion, lateral flexion, and extension of the lumbar spine, it compensates for imbalance between the anterior abdominal muscles
And posterior spinal extensor muscles to stabilize the lumbar spine. Some practitioners believe that most dysfunction of the spine and the hip joint can and should be attributed to a disturbance of function of the psoas and iliopsoas. They postulate that tight or weak psoas muscles are associated with abnormal pelvic tilt, exaggerated lumbar lordosis, lower back pain, sacroiliac dysfunction, degenerative disc disease, scoliosis, and misaligned posture, among other conditions. With extended sitting, a common byproduct of the modern lifestyle, the hip flexors become tight and weak. The psoas and iliopsoas in particular should be addressed in all exercise programs as they affect everyone, from the very active to the sedentary.
The psoas muscles and the abdominal muscles are agonists and antagonists as well as synergists—they can oppose one another's actions and work cooperatively; a dynamic interplay exists between the two muscle groups. The psoas plays an important role in much of the abdominal work in Pilates, particularly in the exercises in which the legs are held up off the ground. Typically, great emphasis is placed on recruitment of the abdominals, while the role of the hip flexors is often minimized or overlooked altogether. I believe that more focus should be placed on controlling and using the hip flexors correctly. They are vital to the successful execution of many Pilates exercises as well as to efficient function and general well-being.