Chapter 10 "Postural Control Mechanisms" and Chapter 11 "Postural Control in Wellness & Performance"
Postural Control Training for Wellness 2 Environment
physical environment, visual field
dynamic balance
the ability to maintain the body in equilibrium during body movment
Modeling Joint Stability
is an outcome of static and dynamic systems, and proactive and reactive postural control.
passive tone
viscoelasticity of the muscle and tendon tissue
Postural Control Training for Wellness 2 Individual
experience, protective equipment, fitness/health, age
Ankle strategy
(dorsi-plantar flexion) provides the quickest way to maintain balance under normal circumstances.
Postural Control within CNS
- anticipatory mechanisms - voluntary control - psychoemotional
secondary core training
Exercises emphasizing noncore movements that require extensive core stabilization
primary core training
Trunk-specific exercises ,because the core is emphasized.
muscle tone dampening
helps smooth out movements.
active tone
level of neural activation of the muscle tissue, mostly a result of reflex activity.
passive vs active tone
maintain a base level of musculoskeletal integrity at rest and during activity.
joint stability
maintains structural integrity of the joint while still permitting motion.
postural control definition
maintenance of body alignment and spatial orientation in order to put the body in a position to enable effective movement.
demanding cognitive challenges and postural control
may tax cognitive resources and postural control may become more variable and less controlled.
Reactive (or compensatory) postural control
occurs in response to postural disturbances.
Proactive (or predictive) postural control
prepares the body for an anticipated postural disturbance.
Change in support postural strategy
stepping and reaching
static balance
the ability to maintain the center of mass within the base of support during relatively steady body positions
Maladaptive Postural Control Biomechanical
causes of poor postural control are numerous.
Coordinating Postural Mechanisms and Levels
- four mechanisms and three levels work together -Research on sway during quiet and perturbed upright stance - body sways like an inverted pendulum and is an intrinsic and necessary property of the motor control system. -Sway helps keep somatosensory, vestibular, and visual systems active. -Forward sway is mostly a property of gravity acting on our mass center. -Corrective sway to upright involves autonomic control or CNS control via pulsed contractions to dorsal side muscles. -Corrective sway also involves stretch reflexes, particularly under large sway. -Tone and reflex sensitivity may serve to regulate the characteristics of the automatic pulsed contractions
Joint Stability Training Programs
- plyometric training -movement quality (instructing) and postural control over fitness development. - imagery alongside instructor verbal and visual cues - core and trunk control and sport-specific perception-action coupling situations. -Situations include fatigue, decision making, external focus of attention, and randomness. -effective programs follow deliberate practice and discovery learning principles with constraints-led approaches.
Postural Control within Neuromuscular Systems
- synergies - coordinative structures
Core Training
- techniques are attempts to contract specific muscles like the transverse abdominis muscle and then coactivate it with internal oblique muscles in a "hollowing" manner. -Such isolation may not be effective in global stabilization. -In this example, the hollowing maneuver leads to a less effective biomechanical profile -Core training can be primary or secondary. - (in image) A. bracing B. hollowing
Postural Control within Musculomechanical
- trunk and posture muscles
Postural Control within Sensory Systems
- vestibular - auditory - visual - somatosensory
Postural Control Training for Wellness: Core Training
-"core" training. -core is the axial skeleton, including shoulder and pelvic girdles, and soft tissue attached to it. -Core musculature activate differently based on movement intentions and outcomes, thus core exercises should be functional and activity specific.
Postural Control
-Alignment and orientation lead to stability and effective positioning. -underlies and enables motor skill execution. -actions are part of motor skill execution. -maintains integrity of the musculoskeletal structures.
Etiology
-Among other risk factors for men and women is fatigue. -Fatigue may be peripheral (local, general) and central.
Maladaptive Postural Control Physiological
-Behavioral states, such as joy and sadness, - numerous causes of poor postural control -systems contribute to postural dysfunction. -Obesity and low fitness contribute to poor postural control characteristics.
Stability and Balance Measurement
-Body segment and joint stability assessments typically look at the spine, shoulder girdle, knee, and ankle. -Standards have been established for some measures. -Some balance measures have been associated with injury and impairments. -Interpreting many balance tests for otherwise healthy individuals are often ambiguous.
Postural Control: CNS Systems
-Conscious control includes deliberate actions to stabilize the body, such as stiffening while walking on ice. -oversees all postural control mechanisms subconsciously or consciously. - sensory reweighting (sensory contributions to balance control) -provides most of the proactive postural control. -CNS-mediated reactive and proactive adjustments can be greatly influenced by learned behaviors and cognitive demands.
Wellness and Postural Control
-Deviations in postural alignment or poor stability contribute to development of health problems, or hamper the development of motor skill proficiency. -definitive cause and effect mechanisms remain elusive -Some postural control problems are a result of pain, injury, disease, behaviors, or habitual misuse.
Measuring Postural Control
-Direct measurement of postural control employs EMG to evaluate muscle activation patterns of postural support muscles during goal-directed movements, perturbed movements, or during quiet stance. -Other clinical and research methods evaluate postural control by measuring postural control outcomes, that is, alignment, segmental stability, joint stability, and whole body balance.
Outcomes of Postural Control Training for Wellness
-Evidence for some improvement in scoliosis and other spinal deformities -Evidence for improvements in spinal segment stability and an associated reduction in trunk musculoskeletal disorders and low back pain
Postural Control and Joint Stability
-Feedforward/proactive postural control required to maintain and ready the joint for disturbances. *Example: Preactivation of knee and ankle musculature controls dampening and force transmission, and braces the joints against destabilizing forces. -In trained individuals, proactive postural control prepares the joints for expected and unexpected stresses and perturbations. -Uncertainty in task requirements creates changes in proactive postural control such that it is more flexible and adaptable. -Reaching to the left or right while in mid-flight may leave an athlete in an unbalanced and vulnerable position upon landing. Proactive stability control to ready the body for off-balance and uncertain landings are necessary to maintain stability of the joints and body as a whole.
Fundamental Postural Strategies:
-In extreme balance challenges, a change-in-support strategy may be used.
Control of Joint Stability
-Joint receptors are many and provide feedback to the CNS regarding joint integrity and joint action. -Two to four types of receptors in joint tissues highlight their importance in monitoring joint function.
Postural Control Training for Wellness
-Most postural control interventions consist of whole body balance exercises on unstable platforms. -Wobble boards and foam surfaces with or without destabilizing forces -Exercises may include single leg stances, jumping, and various strength and power exercises. -Postural control programs for less healthy populations and elders include general strength training, martial arts, and systematically increasing the challenges of activities of daily living.
Cognitive Involvement and Postural Control
-Postural control is mostly background motor activity that works without a great deal of conscious awareness. -Consciously trying to minimize sway interferes with automatic processes and may lead to more sway and less efficiency. -During postural threats, uncertainty, and stress, voluntary postural control often takes over and efficient postural control is lost. -Heights and no handrails are threats and lead to less efficient postural control.
Levels
-Reflexive postural control is primarily a function of somatosensory, vestibular, and visual systems. -Reactive corrections only -Provides ongoing and underlying postural corrections -In cases of disturbed posture, these mechanisms can produce a strong array of reflex actions Example: Righting reflexes to maintain an upright head and overall postural stability.
Can Postural Control Training Improve Sport Performance?
-Sporting activities may contribute to some postural misalignment; necessary adaptations to sport-related training. -Exercises to correct misalignment are largely unsuccessful. -Paucity (presence of something only in small or insufficient quantities) of evidence in athletes and relatively healthy persons associating trunk or core training with sport performance, difficult to assess these relationships -Other types of postural control training may improve some measures related to performance.
Postural Control Training for Wellness 2 Task
-Task-specific functionality follows a systems approach. Example: Guidelines -load handling, complexity, attention demands, fatigue
Researching Postural Control
-Testing for whole body and segmental control and stability outcomes. -Testing for joint stability.
A Postural Control Model
-The complexity of different systems, different levels, and proactive versus reactive postural control can be illustrated by modeling postural control. -Postural control and motor skill mechanisms are shown as separate systems working side by side and interacting. -Essential to this model are internal "schemas" or body plans that provide reference points and requirements for stability and orientation.
"high risk" biomechanical profile.
-The high-risk biomechanical profile includes poor leg muscle coordination leading to poor jumping control, excessive knee wobble, and unstable landing mechanics. -The inward buckling of the knee (valgus) is a key risk factor.
Fundamental Postural Strategies
-Under perturbed stance conditions whole body adjustments to maintain standing balance must begin someplace. -Most corrections generally begin at the support surface, thus at the ankle under most circumstances. -Strategies fall under the categories of fixed point and change in support.
Postural Control: Sensory Systems
-Visual, somatosensory, and vestibular system detect postural changes and provide rapid postural correction through reflexes. -Visual systems provide feedforward control. -Provide low-level tonic corrective reflex actions and large postural corrections to gross perturbations *Crossed extensor reflex supports the body during withdrawal off a pain stimulus.
Measuring Postural Alignment
-Whole body standing posture is measured against a plumb line. -Alignment is also evaluated in body segments, such as spinal alignment. -Interpreting postural faults is challenging
Better Balance Training Programs
-add task-specific functionality and train mechanisms to better recover during a fall. -Should address self-efficacy issues -treadmill drops a board on the path, requiring fall prevention adjustments.
SEGMENTAL STABILITY
-anchoring and stabilizing of body parts to provide a firm foundation upon which other body parts can move -Prevents internal reactive forces from muscle actions to destabilize the rest of the body
Alignment
-biomechanical positioning of body segments and limbs to one another. -Includes whole body alignment (aka "posture") and segment alignment
Risk factors and joint injury
-complex and multifaceted. -Modifiable risk factors center on the "high risk" biomechanical profile.
Postural Control: Neuromuscular Systems
-comprise synergies that provide postural control. Example: Specific patterns of spinal muscle activation in preparation for catching a heavy object, or a learned landing actions during a fall.
Proactive Postural Control
-designed to react to destabilizations and prepare for anticipated disturbances. -mechanisms only participate in reactive control. -Autonomic and voluntary systems provide both reactive and proactive control.
tone
-force the muscle resists lengthening, that is, its stiffness. -controlled by the sensory muscle spindle which measures muscle stretch. -not limited to skeletal muscles, but is also a property of cardiac and smooth muscles.
Balance Training
-integral to any fitness program targeting functional health, including activities of daily living and fall prevention. - in healthy and unhealthy persons improve clinical measures sway and balance. -results can be found across many of these types of methods. -not all programs have equal effects on improving functional balance outside the laboratory
Suspensory strategy
-involves going into a crouched flexed position to lower the center of mass. -More common in those afraid to fall or when in an unfamiliar environment.
Levels of Postural Control: Autonomic
-involves innate and learned behaviors that provide subconscious corrections that are fast and task specific. -In contrast to reflexes, autonimic control is complex, more adaptable to learning, and is both reactive and proactive. -Involves all systems, but mostly neuromuscular and CNS systems -Body lean is an __________ postural action
Levels of Postural Control: Voluntary
-involves those postural adjustments made with conscious awareness. -Entirely a product of the CNS system Example: A novice exerciser playing catch with a heavy medicine ball assumes a highly stiff trunk and leg posture. Some exercisers may consciously stiffen trunk and leg muscles
Postural Control Purposes
-leads to alignment and orientation. -Purpose is to create stable positions ready for diverse actions regardless of positions or motions of the body.
Postural Control and Stability
-main outcome of alignment and orientation is stability. -Upright head orientation maintains visual and vestibular sensation -spinal alignment -Static balance and dynamic balance
Postural control in relative healthy populations
-maladaptive postural control may be a result of sustained workplace postures. -Seated work and repetitive movements are strongly linked to musculoskeletal disorders.
Postural Control in Athletes and Sport
-needs during a sporting action are many. -Poor postural control may lead to an inability to recover from perturbation (system deviation)
Maladaptive Postural Control musculoskeletal
-overt movement actions, and subtle changes in tone and postural control. -Diseases, injuries, and aging contribute to deficits in musculoskeletal strength and integrity, PNS and CNS decline -Seated work and repetitive movements
stability
-position that is resistant to disturbance or returns to its normal state after disruption - a three component interdependent system. -Whole body stability orients the body to prevent or prepare for falls and is better known as balance.
Anticipatory Postural Adjustments
-postural movements that are paired with planned movements and are designed to stabilize joints, body segments, or the whole body prior to the execution of the motor skill. -Before the person can react with an elbow flexion, the gastrocnemius APA activates to prevent the body from being tilted forward.
Postural Control Training for Athletes and Injury Prevention
-provides an uncertain benefit to athletic performance, has resulted in demonstrable reductions in sport-related musculoskeletal injuries. -injuries include ankle knee and sprains, and shoulder injuries. -joint stability. -from joint stability is a static mechanical support system based on joint structure and musculotendinous and ligamentous tissues.
Postural Control Training for Athletes and Sport Performance
-reduce the risk of musculoskeletal injury. -Balance training (not core training) may improve some ability measures in recreational athletes and fit and active persons -Vertical jump height, rate of muscle tension development, and some sport-related and agility tests.
Postural Control: Musculomechanical Systems
-refer to those muscles with large postural roles, such as paraspinal and abdominal muscles, working within biomechanical constraints. -Includes elastic element stiffness, muscle strength, muscle and joint health, joint configurations, and anthropometrics
muscle tone stiffness with postural control
-regulates the storage and release of elastic energy, such as calf muscles during heel strike -Stiff tone prevents heel from crashing down.
Postural Control and Muscle Tone
-serves as a base level of muscle activity for postural control, called postural tone. -Regulates the storage and release of elastic energy -Regulates force dampening
Postural Control Training for Athletes and Sport Performance 3
-should not replace other conditioning programs. -Younger and nonelite athletes more likely to gain benefits -multifaceted, comprehensive, rigorous, and sport specific. -proactive postural mechanisms by uncertainty and rapid decision making, forces postural control systems to "expect the unexpected."
Balance Training 2
-shown to improve laboratory measures of balance in active and athletic populations. -not superior to resistance training for improving the performance or underlying abilities (e.g., sprint speed, jump height) of accomplished athletes.
orientation
-spatial positioning of the body to the environment at any given moment in time, serves to maximize sensory information by placing sensory systems into effective configurations.
muscle tone
-supports posture, and both support goal-directed movements. -must be prepared in advance of movement and react in response to movement.
Following a joint injury the stability of the joint may be compromised for several reasons: (Etiology for Joint Injury)
1. Reduced mechanical stability due to weakened and damaged connective tissues 2. Changes in tissue properties changes the nature of the stimulus-response characteristics of the receptors within the tissue, and subsequently, the nature of the information sent to the CNS. 3. Nociception (harmful stimuli) and pain perception can affect muscle activation and movement behavior.
Whole body stability (balance) measures are mostly:
1. Timed stance, such as single leg stance duration 2. Sway characteristics; subjective or computerized assessment of direction, magnitude, and velocity
Two basic forms of postural control
1. upcoming or expected environmental circumstances or bodily actions to set postural mechanisms in action, based on visual inputs and previous knowledge 2.anticipatory postural adjustments (APAs).
Four chracteristics of APAs
1.modifiable through learning and experience. 2. adaptable to conditions and contexts of movement. 3. influenced by an individual's intention and emotional state. 4. can be either reactionary or anticipatory in order to minimize body displacement during the voluntary movements.
What can reduce postural sway?
A mild cognitive or motor challenge that diverts attention away from posture itself
Postural Control Training Adaptations
Balance training may result in neural changes that maximize subcortical involvement and downgrades cortical and spinal involvement.
sensory reweighting - importante!
CNS monitors multimodal sensory inputs to evaluate stability needs, sometimes emphasizing one input over others.
Fundamental Postural Strategies: Fixed Point
Does not rely as much on foot friction with the support surface
Stability
Left: Knee stability examined with videography while a force plate gathers whole body sway data. Right: Functional reach test for balance.
Whole body static posture:
Little evidence that exercise has an effect in relatively healthy persons.
Postural control in the elderly
Poor vision and hearing, medications and inadequate nutrition may especially degrade postural control
Chapter 10
Postural Control Mechanisms
Chapter 11
Postural Control in Wellness and Performance
Muscle Tone Example:
Postural tone in the vertebral muscles stiffen the column like guy wires (tensioned cable) and prevent against buckling from forces.
Risk factors and joint injury for female athletes and females
Risk factors for female athletes for ankle and knee injuries have been identified as modifiable and nonmodifiable. -Nonmodifiable risk factors in females include less robust joint and ligament structures, greater body fat, and less favorable structural alignment. -Modifiable risk factors center on the "high risk" biomechanical profile.
Body segment stability or alignment:
Targeting specific problems has shown to be more effective than whole body postural alignment, particularly in patients.
Stability and Balance Measurement Image
The "foam-dome" test evaluates problems with specific visual and somatosensory mechanisms by subjectively evaluating sway during different sensory conditions.
Three Levels of Postural Control
The four systems contribute to three levels of postural control. -VOLUNTARY: CNS (VC) -AUTONOMIC: CNS, musculomechanical, neuromuscular, and Sensory (ACMNS) -REFLEXIVE: Musculomechanical and sensory (RMS) -Each of these three levels are simultaneously active, but they do not work to the same extent under all conditions.
Fixed point postural strategy
ankle, hip, and suspensory
Hip strategy
enables more correction and affords a different biomechanical profile than an ankle strategy.