Superficial Back Line (SBL)

Myofascial Meridian

Authors

Affiliations

Nate Yomogida, B.S., SPT

Doctor of Physical Therapy

B.S. in Kinesiology

Chloë Kerstein, B.S., SPT

Doctor of Physical Therapy

B.A. in Neuroscience

Overview

The SBL runs from the plantar foot up the posterior body to the head and wrapping anteriorly to the brow¹. There are 2 distinct pieces: toes to knees and knees to brow¹. The SBL is likened to a “carapace”¹.

Postural Function

Posturally, the SBL helps support the body to attain a fully upright standing position¹. The SBL assists extension and prevents flexing into the fetal position¹.

Since the SBL primarily plays postural roles, its associated muscles have an increased proportion of slow-twitch (type I) muscle fibers which excel at endurance¹.

Since humans spend most of their waking hours fully upright, the SBL is placed under constant load due to postural demand¹. As a result, the fascia adapts to these demands by thickening and creating extra-heavy fascial sheets and bands, as exemplified by the plantar fascia, achilles tendon, within the hamstrings, sacrotuberous lig., thoracolumbar fascia, the “cables” of the erector spinae muscles, and the nuchal lig.¹.

Note

Although the SBL primarily performs extension, a notable exception is the knee joint¹.

The SBL muscles of the hamstring and gastrocnemius function to flex the knee¹. Posturally, the SBL assists full upright stance at the knee through its interlocking tendons at the posterior knee which assist the cruciate ligaments¹.

Common postural compensations

• Ankle dorsiflexion limitation¹
• Knee hyperextension¹
• Hamstring shortness (overuse often due to compensation for dysfunctional deep hip stabilizers)¹.
• Anterior pelvic shift¹
• Sacral nutation¹
• Lordosis¹
• Extensor widening in thoracic flexion¹
• Cervical hyperextension due to Suboccipital limitation¹
• Anterior shift or rotation of the occiput on the atlas (C0-C1)¹.
• Eye–spine movement (oculo-motor reflex) disconnection¹

Movement Function

Other than the knee joint, the SBL primarily functions to create extension or hyperextension¹.

Development

During development, the fetus is in the “fetal position,” and the SBL does not develop much in this position¹.

As babies, we begin to lie in prone and begin to utilize the SBL to extend our neck and head to look around¹. Babies progressively use more distal parts of the SBL moving from just neck to belly, seat, knees, and feet¹.

Details

The SBL is a cardinal myofascial line¹. It acts primarily in the sagittal plane: limiting flexion or creating extension¹.

There are 2 SBLs: right SBL and left SBL¹.

Table 1: superficial back line: Myofascial ‘tracks’ and bony attachments¹

Bony Attachments		Myofascial tracks
frontal bone, supraorbital ridge	13
	12	Galea aponeurotica/ epicranial fascia
Occipital ridge	11
	10	Sacrolumbar fascia / erector spinae
Sacrum	9
	8	Sacrotuberous ligament
Ischial tuberosity	7
	6	Hamstrings
Femoral condyles	5
	4	Gastrocnemius and Achilles tendon
Calcaneus	3
	2	Plantar fascia and short toe flexors
Plantar surface of toe phalanges	1

Toes to Heel

The most distal bony attachment is at the plantar toes¹. The first myofascial track is composed of the plantar fascia and the tendons of the 4 short toe flexors (see Table 2)¹.

Table 2: Short Toe Flexor OIAN

Muscle	Origin	Insertion	Innervation	Action

The 4 short toe flexors and plantar fascia form 5 distinct bands blend into 1 single aponeurosis and attach onto the anterior-inferior aspect of the calcaneus¹. There is a 6th band known as the “lateral band” which runs from the 5th metatarsal base¹.

These fascia and their respective muscles pull across the bottom of the foot to create a “bow-string” with the longitudinal arches¹. This bowstring mechanism aproximates the two ends and keep the proper relationship between the triangulation of the heel, 1st metatarsal head and 5th metatarsal head¹.

Examination

Assess the foot by observing the triangulation between the heel, 5th metatarsal and 1st metatarsal¹.

If the medial foot (Heel to 1st MT)

Heel to Knee

Knee to Hip

Hip to Sacrum

Sacrum to Occiput

Occiput to Supraorbital Ridge

Poly and Monoarticular muscles

Expresses and locals # Bony Attachments Stations

Distal Hamstrings

Separating the Hamstrings

Knee rotation

Plantar fasciitis

Heel Spurs

Test

Forward bend

Derailment

Sacrotuberous ligament

Sacrotuberous ligament

Erector spinae fascia

Suboccipital Muscles

Suboccipitals

Scalp

Neurocranium relationship

General Movement Treatment Considerations

Overall stretches

Specific treatments

Palpation

The SBL and the Waves of the Spine

Is There a Deep Back Line?

References

1.

Myers TW. Anatomy Trains. 4th ed. Elsevier; 2021.