Muscular Units & Postural Distortions Flashcards
Trunk efficiency is especially critical for energy transfer from lower to upper and upper to lower segments; the body relies on two muscle systems:
Inner & outer unit
Inner unit
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
Outer units
(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
Transverse abdominis (TVA): (inner unit)
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
Multifidus (inner unit)
“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
Diaphragm (inner unit)
Serves as a respiratory muscle and local stabilizer via top-down support; can serve both purposes simultaneously
Pelvic floor (inner unit)
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
Posterior oblique sling system:
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
Anterior oblique sling system
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
Deep longitudinal sling system
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
Lateral sling system
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
Reciprocal inhibition
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)
Common postural distortions include:
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)
Winged scapulae
: a lifted and outwardly-rotated scapular position; it appears to protrude posteriorly away from the ribcage - causes shoulder complex dysfunction and potential pain
Upper cross syndrome
: 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
Kyphosis
: 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
Lordosis
: 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
Lower cross syndrome
: 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
Identifying Postural and Muscle Imbalance Issues: facts
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
Categories of Postural Distortions
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
Upper Body Postural Distortions
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
Lumbo-Pelvic-Hip Distortions
Distortions at the lumbo-pelvic regions can occur in the sagittal (lower cross syndrome) and frontal planes (fixed lateral pelvic tilt)
Lower cross syndrome
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
Fixed lateral pelvic tilting:
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
Distal Extremity Distortions
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
