Spine & Thorax Movement Analysis: Isolated & Weighted Crunch

Spine & Thorax Movement Analysis: Isolated & Weighted Crunch

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            I have chosen to analyze the isolated and weighted crunch. Throughout the movement the vertebral column undergoes isometric stabilization, flexion and extension. Many of the muscles of the spine and thorax are involved throughout this movement and will be highlighted in three key positions.

Key Position #1:

            In the first highlighted position the lifter is seen in the starting position, or the upper stopping point if doing multiple repetitions. In this position the extensors of the vertebral column isometrically contract to maintain an upright position against gravity. The extensors of the vertebral column are: Latissimus dorsi, Intertransversarii, Interspinalis, Quadratus lumborum, Spinalis, Semispinalis capitis, Rotatores, Multifidi, Iliocostalis and Longissimus. 

Figure 1, Isometric Extension:

Joint	Muscle	Origin	Insertion	Function	Synergists	Antagonist	Plane
Vertebral column	Latissimus dorsi	Spinous Processes of vertebrae T7-T12, 9th to 12thribs, lumbar and sacral vertebrae via thoracolumbar fascia, iliac crest, inferior angle of scapula	Intertubercular groove of humerus	Extension (isometric)	Longissimus, Iliocostalis, Multifidi, Rotatores, Semispinalis capitis, Spinalis, Quadratus lumborum, Interspinalis, Intertransversarii	Rectus abdominis, External oblique, Internal Oblique, Psoas major, Iliacus	Sagittal
	Intertransversarii	Lumbar: Spanning the transverse processes of vertebrae L-1 to L-5 Cervical: Spanning the transverse processes of vertebrae C-2 to C-7			Longissimus, Iliocostalis, Multifidi, Rotatores, Semispinalis capitis, Spinalis, Quadratus lumborum, Interspinalis, Latissimus dorsi
	Interspinalis	Cervical: Spanning the spinous processes of C-2 to T-3 Lumbar: Spanning the spinous processes of T-12 to L-5			Longissimus, Iliocostalis, Multifidi, Rotatores, Semispinalis capitis, Spinalis, Quadratus lumborum,  Intertransversarii, Latissimus dorsi
	Quadratus lumborum	Posterior iliac crest	Last rib and transverse processes of first through fourth lumbar vertebrae		Longissimus, Iliocostalis, Multifidi, Rotatores, Semispinalis capitis, Spinalis,  Interspinalis, Intertransversarii, Latissimus dorsi
	Spinalis	Spinous processes of the upper lumbar and lower thoracic vertebrae (thoracis). Ligamentum nuchae, spinous process of C-7 (cervicis)	Spinous processes of upper thoracic (thoracis). Spinous processes of cervicals, except C-1 (cervicis)		Longissimus, Iliocostalis, Multifidi, Rotatores, Semispinalis capitis,  Quadratus lumborum, Interspinalis, Intertransversarii, Latissimus dorsi
	Semispinalis capitis	Transverse processes of C-4 to T-5	Between the superior and inferior nuchal lines of the occiput		Longissimus, Iliocostalis, Multifidi, Rotatores,  Spinalis, Quadratus lumborum, Interspinalis, Intertransversarii, Latissimus dorsi
	Rotatores	Transverse processes of lumbar through cervical vertebrae	Spinous processes of lumbar vertebrae through second cervical vertebra		Longissimus, Iliocostalis, Multifidi, Semispinalis capitis, Spinalis, Quadratus lumborum, Interspinalis, Intertransversarii, Latissimus dorsi
	Multifidi	Sacrum and transverse processes of lumbar through cervical vertebrae			Longissimus, Iliocostalis, Rotatores, Semispinalis capitis, Spinalis, Quadratus lumborum, Interspinalis, Intertransversarii, Latissimus dorsi
	Iliocostalis	Common tendon (lumborum). Posterior surface of ribs 1-12 (thoracis and cervicis)	Transverse processes of lumbar vertebrae 1-3 and posterior surface of ribs 6-12 (lumborum). Posterior surface of ribs 1-6 (thoracis). Transverse processes of lower cervicals (cervicis)		Longissimus,  Multifidi, Rotatores, Semispinalis capitis, Spinalis, Quadratus lumborum, Interspinalis, Intertransversarii, Latissimus dorsi
	Longissimus	Common tendon (thoracis). Transverse processes of upper five thoracis vertebrae (cervicis and capitis)	Lower nine ribs and transverse processes of thoracic vertebrae (thoracis). Transverse processes of cervical vertebrae (cervicis). Mastoid process of temporal bone (capitis)		Iliocostalis, Multifidi, Rotatores, Semispinalis capitis, Spinalis, Quadratus lumborum, Interspinalis, Intertransversarii, Latissimus dorsi

Key Position #2:

            During key position number 2 the lifter is seen in full flexion of the vertebral column in order to achieve hypertrophy of her rectus abdominus. Although rectus abdominus hypertrophy is the main goal, there are many other flexor muscles of the vertebral column that work synergistically to perform the movement as seen in the chart below. The primary muscles that cause flexion of the vertebral column are Rectus abdominis, External oblique, Internal oblique, Psoas major and Iliacus. 

Figure 2, flexion:

Joint	Muscle	Origin	Insertion	Function	Synergists	Antagonist	Plane
Vertebral Column	Rectus abdominus	Pubic crest, pubic symphysis	Cartilage of fifth, sixth and seventh ribs and xiphoid process	Flexion	External oblique, Internal oblique, Psoas major, Iliacus	Longissimus, Iliocostalis, Multifidi, ROtatores, Semispinalis capitis, Spinalis, Quadratus lumborum, Interspinalis, Intertransversarii, Latissimus dorsi	Sagittal
	External oblique	External surfaces of fifth to twelfth ribs	Anterior part of the iliac crest, abdominal aponeurosis to linea alba		Rectus abdominis, Internal oblique, Psoas major, Iliacus
	Internal oblique	Lateral inguinal ligament, iliac crest and thoracolumbar fascia	Internal surface of lower three ribs, abdominal aponeurosis to linea alba		Rectus abdominis, External oblique, Psoas major, Iliacus
	Psoas major	Body and transverse processes of lumbar vertebrae	Lesser trochanter		Rectus abdominis, External oblique, Internal oblique, Iliacus
	Iliacus	Upper 2/3 of iliac fossa	Base of lesser trochanter of femur		Rectus abdominis, External oblique, Internal oblique, Psoas major

Key Position #3:

            During the final key position we see the lifter begin the extension phase. Although the cable machine is assisting, the extensors of the vertebral column are still needed to bring the vertebrae back to their starting position. The extensors of the vertebral column are Longissimus, Iliocostalis, Multifidi, Rotatores, Semispinalis capitis, Spinalis, Quadratus lumborum, Interspinalis, Intertransversarii and Latissimus dorsi. 

Figure 3, extension:

Joint	Muscle	Origin	Insertion	Function	Synergists	Antagonist	Plane
Vertebral Column	Longissimus	Common tendon (thoracis). Transverse processes of upper five thoracis vertebrae (cervicis and capitis)	Lower nine ribs and transverse processes of thoracic vertebrae (thoracis). Transverse processes of cervical vertebrae (cervicis). Mastoid process of temporal bone (capitis)	Extension	Iliocostalis, Multifidi, Rotatores, Semispinalis capitis, Spinalis, Quadratus lumborum, Interspinalis, Intertransversarii, Latissimus dorsi.	Rectus abdominis, External oblique, Internal oblique, Psoas major, Iliacus	Sagittal
	Iliocostalis	Common tendon (lumborum). Posterior surface of ribs 1-12 (thoracis and cervicis)	Transverse processes of lumbar vertebrae 1-3 and posterior surface of ribs 6-12 (lumborum). Posterior surface of ribs 1-6 (thoracis). Transverse processes of lower cervicals (cervicis)		Longissimus, ,Multifidi, Rotatores, Semispinalis capitis, Spinalis, Quadratus lumborum, Interspinalis, Intertransversarii, Latissimus dorsi.
	Multifidi	Sacrum and transverse processes of lumbar through cervical vertebrae	Spinous processes of lumbar vertebrae through second cervical vertebra		Longissimus, Iliocostalis, Rotatores, Semispinalis capitis, Spinalis, Quadratus lumborum, Interspinalis, Intertransversarii, Latissimus dorsi.
	Rotatores	Transverse processes of lumbar through cervical vertebrae			Longissimus, Iliocostalis, Multifidi, Semispinalis capitis, Spinalis, Quadratus lumborum, Interspinalis, Intertransversarii, Latissimus dorsi.
	Semispinalis capitis	Transverse processes of C-4 to T-5	Between the superior and inferior nuchal lines of the occiput		Longissimus, Iliocostalis, Multifidi, Rotatores, ,Spinalis, Quadratus lumborum, Interspinalis, Intertransversarii, Latissimus dorsi.
	Spinalis	Spinous processes of the upper lumbar and lower thoracic vertebrae (thoracis). Ligamentum nuchae, spinous process of C-7 (cervicis)	Spinous processes of upper thoracic (thoracis). Spinous processes of cervicals, except C-1 (cervicis)		Longissimus, Iliocostalis, Multifidi, Rotatores, Semispinalis capitis, Quadratus lumborum, Interspinalis, Intertransversarii, Latissimus dorsi.
	Quadratus lumborum	Posterior iliac crest	Last rib and transverse processes of first through fourth lumbar vertebrae		Longissimus, Iliocostalis, Multifidi, Rotatores, Semispinalis capitis, Spinalis, Interspinalis, Intertransversarii, Latissimus dorsi.
	Interspinalis	Cervical: Spanning the spinous processes of C-2 to T-3 Lumbar: Spanning the spinous processes of T-12 to L-5			Longissimus, Iliocostalis, Multifidi, Rotatores, Semispinalis capitis, Spinalis, Quadratus lumborum, Intertransversarii, Latissimus dorsi.
	Intertransversarii	Lumbar: Spanning the transverse processes of vertebrae L-1 to L-5 Cervical: Spanning the transverse processes of vertebrae C-2 to C-7			Longissimus, Iliocostalis, Multifidi, Rotatores, Semispinalis capitis, Spinalis, Quadratus lumborum, Interspinalis, Latissimus dorsi.
	Latissimus dorsi.	Spinous Processes of vertebrae T7-T12, 9th to 12th ribs, lumbar and sacral vertebrae via thoracolumbar fascia, iliac crest, inferior angle of scapula	Intertubercular groove of humerus		Longissimus, Iliocostalis, Multifidi, Rotatores, Semispinalis capitis, Spinalis, Quadratus lumborum, Interspinalis, Intertransversarii

References 

Biel, A. (2014). Trail Guide to the Body (5th ed., pp. 242-260). Boulder, CO: Books of Discovery.