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Chapter 8 Fundamentals of Posture Posture • Posture is the alignment of the body and its parts to accomplish action goal. • Balance is the maintenance of postural equilibrium = Postural Control (context dependent) • Postural Sway is movements with purpose to maintain balance • Static & Dynamic Static Posture • Static = involves little movement – Steady State postures • Standing Posture – – – – Head – erect position Body weight on two feet Bilateral structures, same level-iliac Line of gravity • • • • • • Cervical Thoracic Lumbar Hip Knee Ankle Posterior Anterior + Posterior Posterior Anterior + Anterior + – Spinal curvatures Standing Postures Asymmetric Posture – Weight shift to one leg, with knee fully extended. Anterior LOG to knee creates extensor moment, reduces quad. Activation. Nilotic Stance – One legged stance, with opposite leg supporting behind the knee. Normal Alignment Sitting Posture • Correct sitting posture – always varies, by definition it is one that reduces stress/strain to any one specific region. Lying Posture Surfaces • Hard • Soft • Normal Dynamic Posture • • • • • Walking Running Jumping Throwing Kicking Types of Postural Control • Static PC – COG or LOG within base of support. • Reactive PC – Unexpected shifts to LOG, slipping or tripping, LOG is within BOS. • Anticipatory PC – Adjusting BOS to resist oncoming forces. • Adaptive PC – Context dependent Sensors • Proprioceptors – Muscle Spindle – Golgi Tendon Organ – Joint Receptors – Vestibular Apparatus • Exteroceptors – The … senses Mechanisms of Postural Control Postural Alterations and Pertubations • Changes in postures caused by physiologic, psychological, environmental, anatomic or developmental factors. – Can also be task dependent variations or repeated disturbances(perturbations) Developmental Considerations • Perception-Action Coupling – Respond to environmental cues • Motor Milestones • Bayley Scales of Infant Development – – – – – – – – – – – – – Head erect 1.6 Sitting slight support 2.3 Sitting alone momentarily 5.3 Rolling back-front 6.4 Sitting alone 6.6 Pulling-stand 8.1 Standing up support 8.6 Stepping 8.8 Standing 11 Walking 11.7 Walking backwards 14.6 Walking up stairs 16.1 Jumping 23.4 Postural reactions in infants Older Adults • • • • • • • • • Postural changes Declines in vision Loss of vestibular function Muscle loss Increased sway Impairment of sensory info Slower response/reaction times Decreased ROM Disc issues/pain Postural Dysfunction • • • • • • • • Pain Decreased ROM Muscle loss/imbalances Joint laxity/hypermobility Proprioceptive dysfunction Psyche, environment, defects, fatigue, etc Anatomic changes(pregnancy)/defects Habituation Locomotion: Walking - Gait • Locomotion is the act of moving from place to place • Gait is particular form of locomotion – Walking – Running Walking Gait Cycle • Gait Cycle refers to sequential occurrence of stance and swing phase for a single limb – Stance Phase --- foot contacts ground – Swing Phase --- leg moving forward • Stride period from initial contact of one leg till the next initial contact of the same leg • One stride is two steps • Double Support • Single support • Cadence is the step rate = steps / minute – Velocity = step length * cadence – Velocity = stride length * stride frequency Gait Analysis I Levangie & Norkin (2001) Gait Analysis II According to Perry Temporal and Spatial Characteristics • Normal Walking versus Fast Walking Gait Characteristics • Female & Male – Step length 14% – stride length1.28 to 1.46 – Step width 7 to 9 • 7o direction of progression • 3 mph (1.34m/s) • Younger & Older • Velocity differences • Increase support phase Muscle Activity and Control • Initial Contact and loading response – Hip abductors ecc prevent lateral tilt, knee ext ecc, ankle dorsiflexors ecc • Mid-stance – Plantar flexors ecc control tibia, gastro helps stabilize knee • Terminal Stance – Plantar flexors for push-off • Pre-swing – Hip flexors ( …, gracilis, sartorius) • Initial Swing and midswing – Ankle Dorsiflexors ( …extensor hallucis longus, extensor digitorum longus, peroneus tertius) • Late Swing and Terminal Swing – Ankle Dorsiflexors ecc, knee ext ecc, hamstrings Life Span perspective • Infants – Crawling – Creeping • Gait Characteristics – – – – – – – – Stride Length increase Flat-foot to heel strike Reduced out-toeing Narrow base to anterior-posterior emphasis Knee-extension at Heel Contact & Knee Flexion Midstance Pelvis Rotation Improved Balance reduction in forward inclination Coordination of hands (Contra-lateral) • Older Adults • Trendelenberg gait – paralysis of hip Abductors • ACL-deficient knee – quadriceps avoidance • Cerebral Palsy – muscle dysfunction and paralysis – Spastic Diplegia • Equinus of foot