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Biomechanics of Human MovementBiomechanics of Human Movement
Biomechanics of Balance Biomechanics of Balance
Biomechanics of BalanceBiomechanics of Balance TopicsTopics
Applications Relating to Biomechanics of BalanceApplications Relating to Biomechanics of Balance Determinants of StabilityDeterminants of Stability Factors Influencing StabilityFactors Influencing Stability Role of Sensory Input in BalanceRole of Sensory Input in Balance CNS Strategies for the Maintenance of BalanceCNS Strategies for the Maintenance of Balance Enhancing BalanceEnhancing Balance Assessment of BalanceAssessment of Balance
Biomechanics of BalanceBiomechanics of Balance
ApplicationsApplications
Incidence of FallsIncidence of Falls
Biomechanics of BalanceBiomechanics of BalanceIncidence of FallsIncidence of Falls
1.8 million falls among elderly result in medical treatment
1/3 of all Community-dwelling adults experience at least one fall yearly
Sixth leading cause of death in over 65 age group
Biomechanics of BalanceBiomechanics of Balance
ApplicationsApplications
Incidence of FallsIncidence of Falls Economic Impact of FallsEconomic Impact of Falls
Falls…..Economic ImpactFalls…..Economic Impact
16.4 Billion Dollars annually
Average cost per fall - $9400
48% of cost paid by Medicare
Biomechanics of BalanceBiomechanics of Balance
ApplicationsApplications
Incidence of FallsIncidence of Falls Economic Impact of FallsEconomic Impact of Falls Influence of Pathology and Injury on BalanceInfluence of Pathology and Injury on Balance
Falls…..Influence of Pathology on Falls…..Influence of Pathology on BalanceBalance
Stroke
Alzheimer’s Disease
Head Injury
Parkinson’s Disease
Vestibular Dysfunction
Degenerative Joint Disease
Orthopaedic Joint Injury
Muscle Atrophy
Diminished Balance
Biomechanics of BalanceBiomechanics of Balance
ApplicationsApplications
Incidence of FallsIncidence of Falls Economic Impact of FallsEconomic Impact of Falls Influence of Pathology and Injury on BalanceInfluence of Pathology and Injury on Balance Relationship between balance and posture – Relationship between balance and posture –
implicationsimplications
Balance – Influence on PostureBalance – Influence on Posture
Biomechanics of BalanceBiomechanics of Balance
ApplicationsApplications
Incidence of FallsIncidence of Falls Economic Impact of FallsEconomic Impact of Falls Influence of Pathology and Injury on BalanceInfluence of Pathology and Injury on Balance Relationship between balance and posture – Relationship between balance and posture –
implications implications Sport ConsiderationsSport Considerations
– PerformancePerformance
– Injury PreventionInjury Prevention
Biomechanics of BalanceBiomechanics of Balance
Sport ConsiderationsSport Considerations
Performance
Injury Prevention
Biomechanics of BalanceBiomechanics of Balance
What Causes Instability?What Causes Instability?
Destabilizing “External “Torques Act on Segments Destabilizing “External “Torques Act on Segments • Gravity Gravity
• Distribution and Position of MassDistribution and Position of Mass
• InertiaInertia
• External ForcesExternal Forces
Biomechanics of BalanceBiomechanics of Balance
What Produces Stability?What Produces Stability?
Stabilizing “Internal Torques” Act on Stabilizing “Internal Torques” Act on SegmentsSegments
• Muscle ForcesMuscle Forces• Ligament forcesLigament forces• Distribution and Position of MassDistribution and Position of Mass• External ForcesExternal Forces
Biomechanics of BalanceBiomechanics of Balance
StabilityStability
Internal (Stabilizing) Torques = External (Destabilizing) Torques
Stability is Maintained as long as the:
Biomechanics of BalanceBiomechanics of BalanceFactors Influencing StabilityFactors Influencing Stability
In Practical Terms:
Sensory Factors
Motor Factors
Biomechanical Factors –
Size of the base of support
Height of the COG above the base of support
Mass
BiomechanicsBiomechanicsCenter of GravityCenter of Gravity
Definition – The point around which Definition – The point around which the mass of the body is equally the mass of the body is equally
distributeddistributed
BiomechanicsBiomechanicsCenter of Gravity – Factors InfluencingCenter of Gravity – Factors Influencing
MassMass Location of Mass – position of the body Location of Mass – position of the body
segmentssegments Added (external) massAdded (external) mass
Biomechanics of BalanceBiomechanics of Balance
Control of BalanceControl of Balance
Sensory
CNS
Motor
Biomechanics of BalanceBiomechanics of BalanceSensory Input Sensory Input
Purpose:
To provide the CNS with information about the direction and magnitude of De-Stabilizing Torques
To monitor the effects of Internal Stabilizing Torques
Components:
Vision
Somatosensory
Vestibular
Biomechanics of BalanceBiomechanics of Balance
SomatosensorySomatosensory
Muscle SpindlesMuscle Spindles Joint ReceptorsJoint Receptors Tendon OrgansTendon Organs MechanoreceptorsMechanoreceptors
Biomechanics of BalanceBiomechanics of BalanceVestibular System - The Inner Ear
Head Linear AccelerationHead Linear Acceleration Head Rotation (angular accelerations)Head Rotation (angular accelerations) Head PositionHead Position
The Vestibular System provides information about:
Biomechanics of BalanceBiomechanics of Balance
Sensory Input and ControlSensory Input and Control
1) Activates Supporting Musculature
2) Activates Muscle synergies to produce correction
Sensory Input activates reflexes that (in order):
Biomechanics of BalanceBiomechanics of Balance
CNS and ControlCNS and Control
The CNS Implements “Strategies” that are intended to be selectively applied to various levels of instability
Quiet Stance – maintained by postural alignment, associated joint stiffness and muscle tone
Biomechanics of BalanceBiomechanics of Balance
The Ankle StrategyThe Ankle Strategy
Minimal Instability – the “Ankle Strategy”
Simple ResponseRotation at the ankleInverted Pendulum
Biomechanics of BalanceBiomechanics of Balance
The Hip StrategyThe Hip Strategy
Greater Instability – the “Hip Strategy”
More complexIncreased translation of massAdjustment at Hip
Biomechanics of BalanceBiomechanics of Balance
The Stepping StrategyThe Stepping Strategy
Maximum Instability – the “Stepping Strategy”
Most complex Multiple segments involved Slowest
Biomechanics of BalanceBiomechanics of Balance
Muscle Response to InstabilityMuscle Response to Instability
Muscle Response to Instability Results in a Distal to Proximal Activation Pattern
Gastroc/Soleus – 90 – 100 msec
Hamstrings – 120- 130 msec
Psoas – 130 – 140 msec
Biomechanics of BalanceBiomechanics of BalanceCan Balance Be Improved????Can Balance Be Improved????
YES !!
Sensory Input
CNS Processing
Muscle Output
Cognitive Factors
All capable of Degradation…or…Improvement (sometimes)
Biomechanics of BalanceBiomechanics of BalanceCan Balance Be Improved????Can Balance Be Improved????
Assistive Devices
Evaluating BalanceEvaluating Balance
Force Plate