integrative postural control

stability

refers to ability to counteract forces that disrupt integrity and position of our body, limbs, and joints

postural control

• regulates stability of body, limbs, and joints

• helps prevent injuries of body, limbs, and joints

• facilitates control if motor skills by preventing unwanted movements

  • regulates 3 types of stability: whole body, segmental and joint

whole body stability (balance)

• used to prevent and prepare for falls

segmental stability

facilitates motor skills by preventing body segments and limbs from producing undesired forces and movements (core stability)

joint stability

maintains joint integrity by preventing undesired forces and movements while allowing desired movements (joint mobility)

alignment and orientation

postural control regulates of alignment, orientation, and tone of out body, limbs, and joints

alignment

• positioning of body, limbs, and joints relative to one another

  • helps stabilize body, limbs, and joimys

orientation

• positioning of body, limbs, and joints relative to environment

• facilitates sensory processing used for motor skills

tone

• ability of our body, limbs, and joints to resist movement

  • creates stability by preventing unwanted mobility of body, limbs, and joints

muscle tone

• refers to ability of muscles to resist lengthening (stretch)

  • trade-off between stiffness and compliance

passive muscle tone

• permanent tone created by elasticity of muscle tendon complex

• inherent property of muscle and tendon tissues

  • cannot be actively modified by CNS

active muscle tone

• temporary tone created by activation of muscles by CNS

• involves sensorimotor integration by CNS

  • results from combo of spinal reflexes and subconscious supraspinal mechanisms

postural tone

• use of muscle tone to support postural control

• maintains musculoskeletal stability

• prevents injuries by providing force dampening

• regulates storage and release of elastic energy (neuromechanics)

2 types of postural responses

• postural control involves 2 types of responses: reactive and proactive

reactive postural responses

• produced after destabilization occurs

  • uses sensory feedback to detect ongoing destabilization

proactive postural responses

• produced before destabilization occurs

  • uses feedforward info to anticipate future destabilization

2 subtypes of proactive responses

• 2 subtypes of proactive responses to feedforward info

• sensory evoked proactive responses and anticipatory postural adjustments (APAs)

sensory evoked proactive response

• use feedforward info from vision

  • prevent future destabilization caused by ext forces of environment

anticipatory postural adjustments (APAs)

• use feedforward info from efference copies of motor plans

• prevent future destabilization caused by int forces from body and limb movements used to perform motor skills

  • subconscious feature of motor control

4 mechanisms of postural control

• four sets of mechanisms interact to mediate postural control

1. sensory mechanisms

2. musculomechanical mechanisms (passive)

3. neuromuscular mechanisms (active)

4. CNS mechanisms

sensory mechanisms

• used to initiate reactive and proactive postural responses

• proprioceptive, vestibular, and visual feedback initiate reactive responses (involve multisensory integration)

• feedforward visual info initiate sensory evoked proactive responses (involve integration of visual info w prior knowledge)

musculomechanical mechanisms

• mediate passive postural responses

• mechanical features of musculoskeletal system provide postural stabilization

• structural configurations of body, limbs, and joints facilitate stability

• passive tone of muscle-tendon complex mechanical stability

• elastic elements of muscle tendon complex dampen destabilizing forces

neuromuscular mechanisms

• mediate active postural responses

• intramuscular and intermuscular coordination produce muscle activations

• some patterns of muscle activity are hard-wired (recruitment, reflexes)

• many patterns of muscle activity modified by experience (learning)

CNS mechanisms

• mediate subconscious and conscious postural responses

• CNS networks (spinal, supraspinal) use sensorimotor integration to eval ongoing future destabilization

subconscious responses

include reflexes and learned responses

conscious responses

include deliberate actions used for stabilization

3 levels of postural control

• 3 levels (networks) of CNS mechanisms continuously and simultaneously oversee postural control

  • reflexive, autonomic, and voluntary level

reflexive level

• uses spinal mechanisms to subconsciously initiate reactive responses

• use hard wired, reflex circuits that mediate stereotyped responses (always same not modified by experience)

• always initiated by sensory feedback (somatosensory, vestibular, visual)

• involve interactions b/w CNS, sensory, neuromuscular, and musculomechanical mechanisms

autonomic level

• uses supraspinal mechanisms to subconsciously initiate both reactive and proactive responses

• both reactive and proactive modified through experience → responses adaptable and intelligent

• most effective level of postural control

• compromised of networks and sensory evoked proactive responses involve all 4 mechanisms

• reactive responses and sensory evoked proactive responses involve all 4 mechanisms

• anticipatory postural adjustments (APAs) do not involve sensory mechanisms

voluntary level

• typically uses supraspinal mechanisms to consciously initiate proactive responses

• typically used to anticipate destabilization in situations with limited experience

• responses often ineffective due to limited experience driven adaptation

• involve networks compromised of spinal and supraspinal regions

• emotional factors: disrupt postural control by increasing reliance on voluntary control

• cognitive demands: improve postural control by distracting from voluntary level

postural control model

• involves reactive and proactive responses mediated by interactions b/w 4 mechanisms and 3 levels of postural control

• distinct CNS networks underlie postural control and motor skills but interact to maintain body, limb, and joint stability