Week 4 - Locomotion 1 PDF

Human Locomotion DR JON SHEMMELL MEDI258: HUMAN NEUROMECHANICS Learning objectives: Locomotion 1 u Evolution of upright gait u Why do we walk upright and what have we sacrificed to do it? u Kinematics of gait u Quantification of gait u What are the most important de...

Human Locomotion DR JON SHEMMELL MEDI258: HUMAN NEUROMECHANICS Learning objectives: Locomotion 1 u Evolution of upright gait u Why do we walk upright and what have we sacrificed to do it? u Kinematics of gait u Quantification of gait u What are the most important descriptors of gait? u Determinants of gait u What determines whether we can walk in a stable fashion? u Analysing gait u What do we look for when we analyse gait clinically? Gait A translatory progression of the body as a whole, produced by coordinated rotary movement of body segments. (Napier, 1967, Antiquity of Human Walking) Why bipedal gait? DR JON SHEMMELL MEDI258: HUMAN NEUROMECHANICS Learning objectives: Locomotion 1 u Evolution of upright gait u Why do we walk upright and what have we sacrificed to do it? Upright gait has evolved many times Why two legs? u Advantages of bipedalism u Energetically efficient Locomotor u Improves ability to see predators efficiency in u Impressive display or warning champanzees u Allows non-locomotor forelimb use u Tool use u Carrying u Hunting u Gathering u Improved thermoregulation (important in hot savanna) Why two legs? u Disadvantages of bipedalism u Less stable u Makes one more obvious to predators u Exposes vulnerable body parts to predators u Slower than quadrupedal running (over short distances) u Single limb injuries are more disabling u Energetically expensive to pump blood against gravity u Significantly more loading on spine, pelvis, hips, knees, ankles – increased injury risk u Makes climbing more difficult Implications of bipedalism How has our ancestors’ anatomy had to change to accommodate bipedal gait? u Changes in force production and absorption u Large upper body mass undesirable u Strong pelvis/hip muscles required u Increased reliance on vestibular system  Upright gait has required significant adaptations Quadrupedal Change in position of foramen magnum u The foramen magnum in humans sits directly under the vertex of the Likely bipedal skull u In early hominoids the foramen magnum is positioned towards the Bipedal back of the skull Upright gait has required significant adaptations Change in spinal curvature u Humans have developed additional lumbar spine curvature to allow the pelvis to sit directly under the skull Chimpanzee Human Upright gait has required significant adaptations Change in pelvic shape Upright gait has required significant adaptations Change in leg structure u The angle of the femur is greater in humans than other hominoids u This allows the feet to be placed below the pelvis during the stance phase of gait u Increases shearing forces at the head of the femur Upright gait has required significant adaptations Change in mass distribution u Humans have reduced mass above the waist, which makes maintaining balance easier (Chimpanzee scaled to human height) Upright gait has required significant adaptations Change in foot structure u Reduced size of primary toe u Elimination of opposable digits u Raised arches Main points (Evolution of bipedal gait) u Bipedal locomotion in humans: u It is not clear why bipedal locomotion was originally adopted, although it has many advantages that may have provided a critical survival benefit u Energetically efficient bipedal gait has required major changes in skeletal anatomy Kinematics of human upright gait Learning objectives: Locomotion 1 u Kinematics of gait u Quantification of gait u What are the most important descriptors of gait? u Determinants of gait u What determines whether we can walk in a stable fashion? Kinematics of Gait Phases of the gait cycle: u stance phase (60-65%) u swing phase (35-40%) u double support phase (22%) Gait phase terminology (Rose & Gamble, 1994, p 27) (Rose & Gamble, 1994, p 27) Quantifying gait: distances and times Distance & temporal variables: u Stride length u Linear distance (m) between two successive events accomplished by the same lower extremity during gait u Step length u Linear distance (m) between two successive points of contact of opposite extremities (http://www.optogait.com/Applications/Gait-Analysis) Distance & temporal variables: u Stride duration u time (s) taken to complete one stride u Step duration u time (s) taken to complete one step u Cadence u the number of steps taken per minute u Speed u = cadence x step length u = stride length x stride length Distance & temporal variables: u Width of base of support (Norkin & Levangie, 1992, p 458) Distance & temporal variables: u Degree of toe out Quantifying gait: joint angles Conventions for measuring lower limb joint angles u Essentially displacements from the neutral anatomical posture Ankle motion during walking u Phase 1: Slight plantarflexion (during contact) u Phase 2: Passive dorsiflexion u Phase 3: Active plantarflexion (propulsion) u Phase 4: Active dorsiflexion (during leg swing) u Phase 5: Neutral position (pre- contact) Knee motion during walking u Phase 1: Flexion (after contact) u Phase 2: Extension (support) u Phase 3: Flexion (propulsion) u Phase 4: Further flexion (ground clearance) u Phase 5: Extension (pre- contact) Hip motion during walking u Phase 1: Extension (loading and trunk translation) u Phase 2: Flexion (propulsion) u Phase 3: Slight extension (pre- contact) Motion beyond the sagittal plane Frontal plane pelvic rotation Transverse plane pelvic rotation (Norkin & Levangie, 1992, p 460) Determinants of gait economy FEATURES OF GAIT THAT DETERMINE THE ECONOMY OF LOCOMOTION Determinants of gait economy u Minimising vertical movement of the CoG: u lateral pelvic tilt (pelvic drop) u knee flexion u interaction of joint actions (Norkin & Levangie, 1992, p 462) Determinants of gait economy u Minimising drop in the body’s CoG: u Lateral pelvic tilt reduces the peak CoG position (Norkin & Levangie, 1992, p 462) Determinants of gait economy u Minimising drop in the body’s CoG: u forward and backward pelvic rotation allows legs to remain in a more extended position (Norkin & Levangie, 1992, p 463) Determinants of gait economy u Minimising lateral movements of the CoG: u physiologic valgus at the knee reduces the width of the base of support Determinants of gait economy u trunk motion u upper extremity motion Torques produced around vertical axis cancel to promote forward motion (Norkin & Levangie, 1992, p 463) Main points (Kinematics of gait) u Distance and temporal variables can identify abnormalities and differentiate between different modes of gait u Step/stride length asymmetries u Excessive step width/toe out u Joint kinematics provide insight into movement economy u Important contributions to force absorption/propulsion u Walking economy is assisted by complex joint rotations within and outside the sagittal plane Analysing gait Learning objectives: Locomotion 1 u Analysing gait u Identify the critical features of gait that can differentiate between efficient and inefficient gait patterns Ten critical elements of gait assessments 1. Step length asymmetry 2. Ankle at contact 3. Knee at contact 4. Stance phase knee flexion 5. Duration of single-limb support 6. Ankle and foot angles during push-off 7. Swing phase knee flexion 8. Trunk angle 9. Frontal plane: excess hip drop (Trendelenburg sign) 10. Transverse plane: posture (Kirtley, 2006, p 273) To walk normally… 1. each leg in turn must be able to support the body weight without collapsing 2. balance must be maintained (statically or dynamically) during single limb stance 3. the swinging leg must be able to advance to a position where it can take over the supporting role 4. sufficient power must be provided to make the necessary limb movements and to advance the trunk To walk abnormally… u If someone does not meet one of these 4 requirements – unable to walk u can result from a disorder in any part of the body’s system u can also result from the presence of pain u because the end result is a complicated process, several different original problems may manifest themselves in the same gait abnormality To walk abnormally… u person has no choice, the movement being “forced” on them by weakness, spasticity or deformity u OR u movement is a compensation, which the subject is using to correct for some other problem, which therefore needs to be identified Which factors will affect gait? u age u environment u injury u fitness u clothing u disease u footwear Stroke – hemiplegic gait analysis u Right hemisphere stroke u Left hemiplegia u Otherwise healthy prior to stroke Observations u Slow gait, short stride u Short LT step length u LT ankle limited dorsiflexion u LT knee limited flexion u LT hip hiking u LT arm in fixed flexion Observations: Why? u Short LT mid-stance phase (not providing sufficient stability) u Prolonged RT stance phase (compensatory stability/propulsion) u Short LT GRF (reduced propulsion on left side) u Minimal change in LT knee/ankle joint positions (paralysis/weakness) u Underactive left TA/Gastroc (lack of central drive) Need to know muscles involved in each phase of the gait cycle! See Functional Anatomy (Sutherland et al. 1984; cited Kirtley, 2006, p. 150) Main points (Analysing gait) u Understanding the critical motions that allow economical gait is important for gait analysis u Many factors, including age, injury and neurological disorder affect gait patterns u Analysing gait is the first step in understanding the factors causing an individual’s lack of economy or pain during walking/running