Doctor Steve Abel

Abdominal Muscles

A well-functioning abdominal musculature unloads the back stress during lifting and stabilizes the spinal column, because the abdominal muscles are antagonists to the back muscles. The back muscles are always used during lifting, standing, and sitting. In the majority of people, abdominal muscles are weaker than back muscles. Strong abdominal muscles, hip flexors (iliopsoas, rectus femoris), and back extensors are very important for all sports. There are four abdominal muscles (Table 12-9 and Fig. 12-20).

TABLE 12-5 Long Back Muscles (Intermediate Layer)*

Erector Spinae

Origin

Insertion

Innervation

Action

Iliocostals (lateral column): iliocostalis lumborum, iliocostalis thoracis. and iliocostalis cervicis Longissimus (intermediate column)

Spinalis (medial column): spinalis thoracis, spinalis cervicis, spinalis capitis

Broad tendons attached interiorly to posterior iliac crest, posterior sacrum, sacroiliac ligaments, and sacral and inferior lumbar spinous processes A broad tendon attached inferiorly to posterior iliac crest, posterior sacrum, sacroiliac ligaments, and sacral and inferior lumbar spinous processes Broad tendons attached inferiorly to posterior iliac crest, posterior sacrum, sacroiliac ligaments, and sacral and inferior lumbar spinous processes

Angles of the ribs

Transverse processes of thoracic and cervical vertebrae and mastoid process of temporal bone

Extend from spinous lumbar and thoracic processes

Dorsal rami of spinal nerves of corresponding segments

Dorsal rami of spinal nerves of corresponding segments

Dorsal rami of spinal nerves of corresponding segments

Side bending and ipsilateral rotation when muscles contract unilaterally Trunk extension when muscles contract bilaterally Side bending and ipsilateral rotation when muscles contract unilaterally Trunk extension when muscles contract bilaterally Side bending and ipsilateral rotation when muscles contract unilaterally Trunk extension when muscles contract bilaterally

Semispinalis capitis Splenius capitis

Longissimus capitis Splenius cervicis

Levator scapulae Longissimus cervicis Semispinalis cervicis Iliocostalis cervicis Infraspinatus, infraspinous fascia

Spinalis thoracis Iliocostalis thoracis Longissimus thoracis Iliocostalis lumborum External oblique

Internal oblique

Semispinalis capitis Splenius capitis

Longissimus capitis Splenius cervicis

Internal oblique

Figure 12-18 Muscles of the back.

Ligamentum nuchae Splenius capitis Sternocleidomastoid Splenius cervicis Scalenus posterior

Trapezius Teres major

Serratus posterior superior Rhomboid major

Iliocostalis thoracis Latissimus dorsi Longissimus thoracis Serratus anterior Serratus posterior inferior

Thoracolumbar fascia Erector spinae

Figure 12-18 Muscles of the back.

TABLE 12-6 Average-Length Back Muscles (Deep Layer)

Muscles	Origin	Insertion	Innervation	Action
Semispinalis	Transverse	Medial half between	Dorsal rami of	For corresponding region of spine:
capitis	processes of	superior and	spinal nerves of	ipsilateral rotation when muscles
	T1-T6	inferior nuchal	corresponding	contract unilaterally, extension
		line	segments	when muscles contract bilaterally
Semispinalis	Transverse	Spinous processes	Dorsal rami of	For corresponding region of spine:
cervicis	processes of	of C2-C5	spinal nerves of	ipsilateral rotation when muscles
	T1-T6		corresponding	contract unilaterally, extension
			segments	when muscles contract bilaterally
Semispinalis	Transverse	Thoracic spinous	Dorsal rami of	For corresponding region of spine:
thoracis	processes	processes	spinal nerves of	ipsilateral rotation when muscles
	of thoracic		corresponding	contract unilaterally, extension
	vertebrae		segments	when muscles contract bilaterally
Multifidus	Spinous processes	Spinous processes	Dorsal rami of	Side bending and ipsilateral rotation
	and laminae	spanning one to	spinal nerves of	when muscles contract unilaterally
	from S4-C2	three vertebrae	corresponding	Trunk extension when muscles contract
	vertebrae		segments	bilaterally, stabilizing the spinal
				column

TABLE 12-7 Short Back Muscles (Deepest Layer)*

Muscles	Origin Insertion	Innervation	Action
Intertransversarii	Uniting spinous and transverse processes	Dorsal rami of spinal	Laterally flex superior
	of consecutive vertebrae	nerves of corresponding	vertebra; help extend
		segments	vertebral column
Interspinalis	Uniting spinous and transverse processes	Dorsal rami of spinal	Help extend vertebral
	of consecutive vertebrae	nerves of corresponding	column
		segments
Rotatores	Transverse process Base of spinous	Dorsal rami of spinal	Rotate superior
	of vertebra process of	nerves of corresponding	vertebra to the
	superior vertebra	segments	opposite side

*See Figure 12-19.

*See Figure 12-19.

Costotransverse ligament

Levator costae longus Levator costae brevis Rotatores thoracis

Lumbalis vertebra I, vertebral arch

Ligamenta flava

Intertransversarii mediales lumborum

Intertransversarii mediales lumborum

Intertransverse ligament

Rib IX

Multifidi

Intertransverse ligament

Lumbar vertebrae, spinous processes

Figure 12-19 Deep short muscles of the back.

Intertransverse ligament

Rib IX

Multifidi

Intertransverse ligament

-Rib XII

Lumbar vertebrae, processes costal Intertransversarii laterales lumborum Thoracolumbar fascia (deep layer)

Multifidi

Erector spinae

Lumbar vertebrae, spinous processes

Figure 12-19 Deep short muscles of the back.

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