Balance

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Balance Postural Equilibrium
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• Factors impacting balance
• Muscular weakness
• Proprioceptive deficits
• ROM deficits

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Terminology

• Balance - Process of maintaining bodys CoG
  within base of support
• Bodys CoG rests slightly above the pelvis
• Ability to align body segments against gravity to
  maintain or move the body within the available
  base of support without falling (Kisner Colby,
  2002, 4th ed.)
• Strength is emphasized before proprioception in
  rehab because strength influences balance
• Postural equilibrium - broader term that
  incorporates alignment of joint segments
• Maintaining CoG (Center of Gravity) within the
  limits of stability (LOS)
• Proprioception bodys ability to transmit
  position sense, interpret info respond
  consciously/unconsciously to stimulation
• Coordination smooth pattern of activity is
  produced through a combo of muscles acting
  together with appropriate intensity timing
• Agility ability to control the direction of a
  body or segment during rapid movement

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Postural Control System

• 3 Components of the system
• Sensory detection of body motions
• Visual
• Vestibular
• Somatosensory inputs
• Integration of sensorimotor information within
  the CNS
• Execution of musculoskeletal responses
• Balance is both a static dynamic process

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Control of Balance

• Tall body vs. Small base of support
• Balance relies on network of neural connections
• Postural control relies on feedback
• CNS involvement
• Sensory organization
• Determines timing, direction amplitude of
  correction based on input
• System relies on one sense at a time for
  orientation
• Muscle coordination
• Collection of processes that determine temporal
  sequencing distribution of contractile activity

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• Sensory Input
• Vision
• Measures orientation of eyes head in relation
  to surrounding objects
• Helps maintain balance
• Vestibular
• Provides info dealing with gravitational, linear
  angular accelerations of the head with respect
  to inertial space
• Minor role when visual somatosensory systems
  are operating correctly
• Somatosensory
• Provides info concerning relative position of
  body parts to support surface each other
• Somatosensation Proprioceptive system
• Specialized variation of the sensory modality of
  touch, encompassing joint sense (kinesthesia)
  position
• Process
• Input from mechanoreceptors
• Stretch reflex triggers activation of muscles
  about a joint because of perturbation
• Results in muscle response to compensate for
  imbalance and postural sway
• Muscle spindles sense stretch in agonist, relay
  information afferently to spinal cord
• Information is sent back to fire muscle to
  maintain postural control

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• Body position in relation to gravity is detected
  by sensory input
• Balance movements involve a number of joints
• Ankle
• Knee
• Hip
• Coordinated movement along kinetic chain

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Prentice, 2004, 4th ed.
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Balance relating to the CKC

• Kinetic chain
• Each moving segment transmits forces to every
  other segment
• Maintaining equilibrium involves the closed
  kinetic chain
• (foot distal segment ? fixed beneath base of
  support)
• Automatic postural movements
• Determined via indirect forces created by muscles
  on neighboring joints
• Series of joint strategies are involved to
  coordinate movement
• Injury to joints or corresponding muscles can
  result in loss of appropriate feedback
• Steadiness - Ability to keep body as motionless
  as possible
• Measure of postural sway

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• Postural sway
• Deviation from Center of Pressure, Balance
  Vertical Force (CoP, CoB, or CoF)
• Determined using mean displacement, length of
  sway path, length of sway area, amplitude,
  frequency and direction relative to CoP
• Symmetry - Ability to distribute weight evenly
  between 2 feet in upright stance. Measures
• Center of Pressure (CoP)
• Center of distribution of the total force applied
  to the supporting surface
• Center of Balance (CoB)
• Point between feet where the ball heel of each
  foot has 25 of the body weight
• Relative weight positioning
• Center of Vertical Force (CoF)
• Center of vertical force exerted by the feet
  against the support surface

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Balance Disruption

• Balance Deficiencies - Inappropriate interaction
  among 3 sensory inputs
• 2 Factors that Disrupt Balance
• Position of CoG relative to base of support is
  not accurately sensed
• Automatic movements required to maintain the CoG
  are not timely/effective
• In the event of contact, the body must be able to
  determine what to do in order to control CoG
• Joint mechanoreceptors initiate automatic
  postural response

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Selecting Movement Strategies during Balance
Disruption

• Joints (Ankle, Knee Hip) involved allow for a
  wide variety of postures that can be assumed in
  order to maintain CoG
• Forces exerted by pairs of opposing muscles at a
  joint to resist rotation (joint stiffness)
• Resting position joint stiffness are altered
  independently due to changes in muscle activation
• Myotatic or Stretch Reflex is earliest mechanism
  for activating muscles due to externally imposed
  joint rotation

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• Ankle Strategy
• Shifts CoG by maintaining feet rotating body at
  a rigid mass about the ankle joints
• Gastrocnemius or tibialis anterior are
  responsible for torque production about ankle
• Anterior/posterior sway is counteracted by
  gastrocnemius tibialis anterior, respectively
• Effective for slow CoG movements when base of
  support is firm within LOS
• Also effective when CoG is offset from center

• Hip Strategy
• Relied upon more heavily when somatosensory loss
  occurs forward/backward perturbations are
  imposed or support surface lengths are altered
• Aids in control of motion through initiation of
  large rapid motions at the hip with anti-phase
  rotation of ankle
• Effective when CoG is near LOS perimeter when
  LOS boundaries are contracted by narrower base of
  support

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• Stepping Strategy
• Utilized when CoG is displaced beyond LOS
• Step or stumble is utilized to prevent a fall
• Instance of musculoskeletal abnormality
• Damaged tissue result in reduced joint ROM
  causing a decrease in the LOS placing
  individual at a greater risk for fall
• Research indicates that sensory proprioceptive
  function is affected when athletes are injured

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Assessment of Balance

• Subjective Assessment
• Romberg Test traditional assessment
• Balance Error Scoring System (BESS)

Prentice, 2004, 4th ed.
Google Images
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• Semi-dynamic dynamic tests
• functional reach tests
• timed agility tests
• carioca
• hop test
• Timed T-band kicks
• Timed balance beam walks (eyes open closed)

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• Objective Assessment
• Balance systems
• Provide for quantitative assessment training
  static dynamic balance
• Easy, practical cost-effective
• Utilize to assess
• Possible abnormalities due to injury
• Isolate various systems that are affected
• Develop recovery curves based on quantitative
  measures in order to determine readiness to
  return
• Train injured athlete
• Computer interfaced force-plate technology
• Vertical position of CoG is calculated
• Vertical position of CoG movement indirect
  measure of postural sway

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Prentice, 2004, 4th ed.

• Force plate measures
• Steadiness, symmetry, dynamic stability
• Total force applied to the platform fluctuates
  due to body weight and inertial effects of body
  movement
• Forces based on motion of CoG
• Allows for static dynamic postural assessment
• Single or double leg stance, eyes opened or
  closed
• Moving visual surround for sensory isolation
  interaction

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• Dynamic stability - Ability to transfer vertical
  projection of CoG around a stationary supporting
  base
• Perception of safe limit of stability
• Utilization of external perturbation
• Some are systematic while others are
  unpredictable determined via changes in subject
  sway
• Athlete should maintain their CoP near A-P and
  M-L midlines

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Injury Balance

• Stretched/damaged ligaments fail to provide
  adequate neural feedback, contributing to
  decreased balance proprioception
• May result in excessive joint loading
• Could interfere with transmission of afferent
  impulses
• Alters afferent neural code conveyed to CNS
• Decreased reflex excitation
• Caused via a decrease in proprioceptive CNS input
• May be the result of increased activation of
  inhibitory interneurons within the spinal cord
• All of these factors may lead to progressive
  degeneration of joint continued deficits in
  joint dynamics, balance coordination

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• Ankles
• Joint receptors believed to be damaged during
  injury to lateral ligaments
• Less tensile strength when compared to ligament
  fibers
• Results in deafferentation and ? signaling via
  afferent pathways
• Articular deafferentation reason behind
  balance training in rehabilitation
• Orthotic bracing intervention
• Enhancement of joint mechanoreceptors to detect
  perturbations provide structural support for
  detecting controlling sway
• Modify movement strategies to enhance
  proprioceptive input
• Altered biomechanical alignment alters
  somatosensory transmission

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• Knee Injuries
• Ligamentous injury has been shown to alter joint
  position detection
• ACL deficient subjects with functional
  instability exhibit this deficit which persist to
  some degree after reconstruction
• May also impact ability to balance on ACL
  deficient leg
• More dynamic testing may incorporate additional
  mechanoreceptor input results may be more
  definitive

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• Head Injury
• Balance has been utilized at a criterion variable
• Additional testing is necessary in addition to
  balance sensory techniques
• Postural stability deficits
• Deficits may last several days post-injury
• Result of sensory interaction problem - visual
  system not used effectively
• Objective balance scores can be used to determine
  recovery curves for making return to play
  decisions

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Balance Training

• Vital for successful return to competition from
  lower leg injury
• Possibility of compensatory weight shifts and
  gait changes resulting in balance deficits
• Functional rehabilitation should occur in the
  closed kinetic chain nature of sport
• Adequate AND safe function in the open chain is
  critical first step in rehabilitation

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Rules of Balance Training

• Exercise must be safe challenging
• Stress multiple planes of motion
• Incorporate a multisensory approach
• Begin with static, bilateral stable surfaces
  progress to dynamic, unilateral unstable
  surfaces
• Progress towards sports specific exercises
• Utilize open areas
• Assistive devices should be in arms reach early
  on
• Sets and repetitions
• 2-3 sets, 15 ? 30 repetitions or
• 10 of the exercise for 15 ? 30 seconds later on
  in the program

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Classification of Balance Exercises

• Static -
• CoG is maintained over a fixed base of support,
  on a stable surface
• Semi-dynamic
• Person maintains CoG over a fixed base of support
  while on a moving surface
• Person transfers CoG over a fixed base of support
  to selected ranges and or directions within the
  LOS, while on a stable surface
• Dynamic
• Maintenance of CoG within LOS over a moving base
  of support while on a stable surface (involve
  stepping strategy)
• Functional
• Same as dynamic with inclusion of sports specific
  task

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Prentice, 2004, 4th ed.

• Phase I
• Non-ballistic types of drills
• Static balance training
• Bilateral to unilateral on both involved
  uninvolved sides
• Utilize multiple surfaces to safely challenge
  athlete maintaining motivation
• With without arms/counterbalance
• Eyes open closed
• Alterations in various sensory information
• ATC can add perturbations
• Incorporation of multiaxial devices
• Train reflex stabilization postural orientation

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• Phase II
• Transition from static to dynamic
• Running, jumping and cutting activities that
  require the athlete to repetitively lose and gain
  balance in order to perform activity
• Incorporate when sufficient healing has occurred
• Semi-dynamic exercised should be introduced in
  the transition
• Involve displacement or perturbation of CoG
• Bilateral, unilateral stances or weight transfers
  involved
• Sit-stand exercises, focus on postural

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Bilateral Stance Exercises
Prentice, 2004, 4th ed.
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Prentice, 2004, 4th ed.

• Unilateral Semi-dynamic exercises
• Emphasize controlled hip flexion, smooth
  controlled motion
• Single leg squats, step ups (sagittal or
  transverse plane)
• Step-Up-And-Over activities
• Introduction to Theraband kicks
• Balance Beam
• Balance Shoes

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• Phase III
• Dynamic functional types of exercise
• Slow to fast, low to high force, controlled to
  uncontrolled
• Dependent on sport athlete is involved in
• Start with bilateral jumping drills straight
  plane jumping patterns
• Advance to diagonal jumping patterns
• Increase length and sequences of patterns
• Progress to unilateral drills
• Pain fatigue should not be much of a factor
• Can also add a vertical component to the drills
• Addition of implements
• Tubing, foam roll
• Final step functional activity with
  subconscious dynamic control/balance

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Phase III Exercises
Prentice, 2004, 4th ed.
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References

• Prentice, W.E. (2004). Rehabilitation Techniques
  for Sports Medicine and Athletic Training, 4th
  ed., McGraw-Hill
• Houglum, P.A. (2005). Therapeutic Exercise for
  Musculoskeletal Injuries, 2nd ed., Human
  Kinetics.
• Kisner, C. Colby, L. (2002). Therapeutic
  Exercise Foundations Techniques, 4th ed., F.A.
  Davis.
• http//www.google.com - Images