Muscular Units & Postural Distortions

Question 1

Trunk efficiency is especially critical for energy transfer from lower to upper and upper to lower segments; the body relies on two muscle systems:

Answer 1

Inner & outer unit

Question 2

Inner unit

Answer 2

local stabilizers that support the spine/pelvis

collective group of local spinal and pelvic stabilizers; includes the transverse abdominis, diaphragm, posterior internal oblique, pelvic floor, and multifidus

Question 3

Outer units

Answer 3

(myofascial sling systems) – global stabilizers that work reactively to control body segments and provide functional force closure

global systems that function to stabilize the spine/pelvis during movement involving the extremities; works with the inner unit to transfer force to the hands/feet across the trunk

Question 4

Transverse abdominis (TVA): (inner unit)

Answer 4

Helps maintain proper intra-abdominal pressure to manage flexion/extension of the spine

Enhances rigidity of the thoracolumbar fascia to improve bracing of the lumbo-pelvic region (“natural weight belt effect”)

Delayed firing of this muscle is associated with poor core stability and lower back pain

Question 5

Multifidus (inner unit)

Answer 5

“Hoop tension” is created between the TVA and the multifidi which connect moving segments of the vertebrae – a circle of stability like a belt

Contracts with the TVA to prevent undesirable changes in spinal segment positioning

Question 6

Diaphragm (inner unit)

Answer 6

Serves as a respiratory muscle and local stabilizer via top-down support; can serve both purposes simultaneously

Question 7

Pelvic floor (inner unit)

Answer 7

Stabilizes the front and back by acting on the pelvis, may initiate and capture force within the inner unit

Anchors the pelvic girdle in response to bracing and loading

Question 8

Posterior oblique sling system:

Answer 8

Includes the latissimus dorsi, gluteus maximus, and thoracolumbar fascia
Integrates with central stabilizers to form a structural “force transfer bridge” between the lumbar spine and pelvic girdle

Issues with the system can impact forces that contribute to speed, strength, and power

Question 9

Anterior oblique sling system

Answer 9

Complementarily opposes the posterior oblique system via the combined function of the obliques, adductors, and abdominal fascia

Creates cross-stabilization for the anterior sling and is integral to sagittal plane locomotion

Question 10

Deep longitudinal sling system

Answer 10

Includes the erector spinae and thoracolumbar fascia (low back), multifidus, and sacrotuberous ligament connecting with the hamstrings; extends to the lower extremities

Connects multiple joint segments for efficient sprinting mechanics due to combined extension of the hip and knee

Question 11

Lateral sling system

Answer 11

Includes the hip abductors, quadratus lumborum, and thigh adductors to provide frontal plane stability and aid in vertical/horizontal bipedal and climbing motions

Stabilizes hip loading for actions such as climbing a ladder and stepping up stairs

Question 12

Reciprocal inhibition

Answer 12

neuromuscular regulation of agonist-antagonist contraction patterns to reduce resistance during opposing joint actions; allows fluid movement and activation patterns

Many issues arise as changes in joint position cause changes in biomechanics; muscles become imbalanced and reciprocal inhibition may occur within functional units (e.g., inhibition of the abdominals and glutes due to excessively tight hip flexors)

Question 13

Common postural distortions include:

Answer 13

Forward head posture and/or rounded shoulders
Winged scapulae
Upper cross syndrome
Kyphosis of the thoracic spine
Lordosis of the lumbar spine and lower cross syndrome
Undesirable fixed pelvic tilting
Lower extremity distortions (impact knees and ankles)

Question 14

Winged scapulae

Answer 14

: a lifted and outwardly-rotated scapular position; it appears to protrude posteriorly away from the ribcage - causes shoulder complex dysfunction and potential pain

Question 15

Upper cross syndrome

Answer 15

: upper body postural distortion that presents as a forward head, raised, internally-rotated, or rounded/forward shoulders with an exaggerated thoracic curvature; contributes to upper back pain, shoulder dysfunction and training limitations for the upper body

Question 16

Kyphosis

Answer 16

: excessive convex curvature of the thoracic spine presenting as a bowed/rounded back; contributes to upper back pain and a significant decline in shoulder mobility

Question 17

Lordosis

Answer 17

: excessive concavity or inward curvature of the lumbar spine; usually presents as part of the lower cross syndrome and contributes to lower back pain and hip dysfunction

Question 18

Lower cross syndrome

Answer 18

: lower body distortion characterized by an undesirable anterior tilt of the pelvis with lordosis due to severe muscular imbalance in the lumbo-pelvic region; contributes to significant core instability, lower body training limitations and lower back pain

Question 19

Identifying Postural and Muscle Imbalance Issues: facts

Answer 19

A plumb line can be used to observe static variations in anatomical positions caused by postural distortions

A plumb line should go through the following locations from top to bottom:

The earhole
Acromioclavicular joint
Central vertebral bodies
Greater trochanter of the hips
Slightly anterior to the midline of the knee
Anterior portion of the lateral malleolus through the calcaneocuboid joint

Each client should be evaluated for issues in both static and dynamic postures; fixing these issues starts by recognizing problem areas

Postural and phasic muscles are often too tight and/or overactive or too weak and/or underactive

Overactivity = postural muscles tend to become immobile; phasic muscles tend to weaken

Question 20

Categories of Postural Distortions

Answer 20

Postural distortions are categorized into clinically-diagnosed musculoskeletal problems, including:

Upper body/extremity distortions: forward chin, kyphotic exaggeration, upper cross syndrome, Dowager’s hump (osteoporotic microfractures)

Lumbo-pelvic-hip distortions: lower cross syndrome, fixed pelvic tilting
Lower/distal-extremity distortions: knee rotation and ankle pronation/supination issues

Question 21

Upper Body Postural Distortions

Answer 21

Upper body segments commonly migrate forward; common issues include shoulder joint dysfunction, winged scapulae, impingement syndrome and kinetic chain disturbances

Forward chin – upper trapezius and levator scapulae become overactive while reciprocating muscles of the scapula become underactive

Progression into rounded shoulders/kyphosis – mid/lower trapezius becomes less active, serratus anterior becomes overactive, rhomboids/pectorals activate improperly

Upper cross syndrome:
The shoulders are pulled forward/rounded

The latissimus dorsi, teres major, subscapularis, and pectoralis become shortened, strong and overactive

The infraspinatus, teres minor, rhomboids, and mid/low trapezius become lengthened and weak

The posterior joint capsules tighten, further limiting the ability of the glenohumeral heads to migrate posteriorly

Question 22

Lumbo-Pelvic-Hip Distortions

Answer 22

Distortions at the lumbo-pelvic regions can occur in the sagittal (lower cross syndrome) and frontal planes (fixed lateral pelvic tilt)

Question 23

Lower cross syndrome

Answer 23

Reciprocal weakness and tightness of the musculature attaching to the pelvic girdle

Commonly caused by poor posture, sedentary behaviors which shorten the hip flexors, and imbalanced, bilateral lower body training using an arched back

Characterized by undesirable anterior pelvic tilting, core instability, and lower back pain

A chronic anterior pelvic shift shuts off the core muscles as the hip flexors and low back manage central stability

Exaggerated lumbar lordosis - gluteals, abdominals, and spinal stabilizers are underactive; calves, hip adductors, hamstrings, erector spinae, rectus femoris, and hip flexors are overactive

Question 24

Fixed lateral pelvic tilting:

Answer 24

Presents as a hip elevation (“hiking up”) on one side of the pelvis while the opposing side is depressed - ↑ hip adduction on raised side, ↑ hip abduction on lowered side

Creates problems with locomotion, leg length disparities, frontal plane stability, combined knee and hip flexion (squats), and hip or midback pain

Primary overactive problem areas: QL, psoas group, and adductors on the elevated side; hip abductors (gluteus medius, TFL) on the depressed side

Can be caused by single-side dominant postures, lower limb injuries (e.g., ankle) or performing repeated actions in the same plane

Question 25

Distal Extremity Distortions

Answer 25

Tibial-femoral dysfunction refers to distortions seen at the knee and ankle joints:

Ankle over-pronation (flat feet) or ankle over-supination

Varus knees (bow-legged) due to external rotation at the hip

Valgus knees (knees in, heels inward, toes pointing out) due to internal rotation at the hip

A combination of the above (e.g., knees in with flat feet)

Key concept: biomechanical adjustments in the hip changes pelvic-femoral positioning which distorts the lower extremities (makes them harder to diagnose)
Examples:

Feet are pronated and the knees move in:

Overactive vastus lateralis, biceps femoris, and adductors with weak gluteals and vastus medialis inefficiency
Feet “turn out” and heels rotate inward:
Overactive calves and hamstrings with underactive adductors

Common injuries associated with knee/ankle distortions: plantar fasciitis, shin splints, IT band syndrome and jumper’s knee