The muscular system
Paravertebral
muscles cooperate with abdominal
and psoas muscles
in keeping the back straight, resembling the opposing ropes holding
a ship's mast. The glutei
attach the spine to the pelvis and assure stability to the muscular
system.
On the other hand, if muscles at the posterior face of the thigh
(ischiotibial)
are shortened, there is a tendency to inadequate spinal postures.
Muscles are very innervated; lesions or overload
may be very painful.
Lateral view
1. Abdominals
2. Psoas
3. Glutei
4. Paravertebral |
The abdominal muscles
They extend from the lower margin of the ribs to the upper pelvis,
protecting inner organs. Muscles on the front portion are named
"anterior rectus". When contracting they bring ribs near
the pelvis frontward, bending the spine forward, but these muscles
are not efficient in terms of movement: when they are at their utmost
contraction the spine only curves about 30 degrees forward.
The abdominal muscles placed on the lateral portion of the trunk
are named "oblique" and "transversus". When
the left transversus contracts, ribs are brought near the pelvis
on the left side, making a wider separation on the right side between
the ribs and the pelvis. When the oblique ("major" and
"minor") contract, hips rotate without moving the shoulder.
If they contract along with the anterior rectus, they bring ribs
near the pelvis in a crossed fashion, the right shoulder toward
the left hip or viceversa.
The transversus contraction acts as a girdle, keeping viscera tightly
against the spine.
The paravertebral muscules
They extend throughout the back of the trunk. Paravertebral muscles
unite the posterior lower portion of the ribs with the pelvis, and
attach vertebrae one on top of the other, and these with the scapula.
When contracting, the vertebral "tails" (spinous processes)
come closer, straightening the trunk and bending it backward.
The psoas muscle
The psoas extends from the last thoracic vertebra along the five
lumbar vertebrae to the thigh, crossing the pelvic region. When
contracting, the leg is brought forward near the vertebrae until
the chest touches the knee.
When flexing the spine forward, the psoas is more efficient than
abdominal muscles, in terms of movement. The abdominal and the psoas
muscles jointly contribute to the first 30-degree flexion; past
this angle, only the psoas permits the spine to continue bending
forward.
The gluteus
The gluteus extends from the pelvis to the posterior part of the
femur, forming the buttocks. When contracting they pull the leg
backward and outward. When extending the back backwards, the gluteus
and ischiotibial muscles cooperate with the paravertebral muscles.
The gluteus and other pelvic muscles, such as the pyramidal, maintain
a dynamic tension within the pelvic waist, providing a stable support
to the spine.
The ischiotibial muscles
They extend along the posterior part of the thigh, from the back
of the pelvis to the knee. During back extension, the glutei and
the ischiotibial muscles cooperate with paravertebral muscles.
If ischiotibial muscles are shortened, the lumbar area is consistently
arched more than normal - which is known as lordosis
- and may result in paravertebral muscle contraction.
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