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  1. 1. Kinesiology
  2. 2. 7.5- Interaction between COM motion (characterized by velocity on the y axis and displacement on the x-axis) and type of response used to recover stability following an external perturbation.
  3. 3. • Shaded area indicates when the COM will cause a step in order to maintain stability• First movement the COM stays within the limits and person uses ankle strategy• The second trajectory puts the COM outside the stability limits forcing the step• The third trajectory requires a step because the initial COM velocity is high and the movement is short
  4. 4. 7.9
  5. 5. • Shows typical synergy w/ loss of balance and use of ankle strategy; used for small perturbations• Muscles react 90-100 msec after perturbation w/o synergy of hamstring and paraspinal muscles, indirect effect of gastroc. Ankle torque on prox body segments would result in forward motion of trunk mass relative to lower extremities• Muscles are activated distal to proximal• Responses have been hypothesized to be activated in response to visual and vestibular inputs referred to as M3 responses
  6. 6. 7.10: Muscle synergy and body motionsassociated with hip strategy for controlling forward and backward sway
  7. 7. • A)The typical synergistic muscle activity associated w/ hip strategy• Motion of the platform in the backward direction causes the subject to sway forward• Muscles activity begins @ about 90 to 100 msec after perturbation onset in the abdominal muscles followed by activation of quads• B)muscle pattern associated with hip strategy correcting for backward sway• Used to restore equilibrium in response to larger, faster perturbations
  8. 8. 7.15 the six sensory conditions used to test how peopleadapt the senses to changing sensory conditions during maintenance of stance
  9. 9. • Conditions 4 to 6 are identical to 1 to 3 except that the support surface now rotates with body sway• Difference in amount of body sway in these conditions determine subjects ability to adapt• Children over the age of 7 adapt easily
  10. 10. 7.18 anticipatory postural activity associated with lifting a weight from the subjects arm
  11. 11. • Subject of experimenter lifted a 1 kg weight from subject forearm in active unloading by subject, theres a prepatory bicep inhibition to keep arm from moving upward when it was unloaded• Anticipatory reduction in bicep EMG of arm holding load was time-locked with the onset of activation of the biceps of lifting arm• This reduction is not seen during passive unloading• Postural adjustments are organized at the bulbospinal level and the pyramidal tract activates these pathways as it send descending commands to the prime mover• While the basic mechanisms for postural adjustment may be organized at this level, they appear to be modulated by several parts of the nervous system including the cerebellum
  12. 12. 9.11- single and dual task paradigms. Posturaland cognitive task performance is measured in isolation
  13. 13. • A. single vs dual task• B. Contraction onset for the gastroc muscle for young, healthy adults and balance impaired older adults• All three groups show delays in the dual task vs single• EMG magnitude of the gastroc• Healthy and balance impaired older adults show a reduction of response amplitude in the dual task conditions
  14. 14. 10.8
  15. 15. • Parkinsons disease coactivates antagonistic muscles around hip and knee• This activation results in a stiffening of the body and is very inefficient for recovery balance• Rigidity and loss of balance found in patients during tilt tests imply equilibrium reactions were absent• Patients respond to dis equilibrium but the pattern of muscle activity is eneffective in recovering balance
  16. 16. 10.13: EMG activity in controls (A) versus persons with anterior lobe cerebellar degeneration
  17. 17. • Hypermetric postural responses found in people w/ anterior-lobe cerebellar damage• Responses in people w/ cerebellar disease are LARGER in amplitude & longer in duration than controls• Hypermetric muscle activity resulted in excess torque and overcorrection in sway during recovery of stability• Multidirectional perturbations postural responses are LARGER than normal in people w/ MS--> to compensate for delayed onset of contraction• The larger postural responses seen in MS subjects were similar but not as large as the hypermetric postural responses seen in
  18. 18. 10.14
  19. 19. • PD= inability to change movement strategies quickly to adapt to changes in support surface characteristic• PD subjects had to maintain balance in various situations• Control group was able to modify postural muscle responses quickly in response to changing task demands; PD couldn’t• Results show that basal ganglia functions to prime or set the nervous system to achieve goal• PD had difficulty changing from 1 movement to another• Reduced ability to modify postural strategies has been shown in response to multidirectional surface perturbations and resonse to changing stance width
  20. 20. 12.5 brain and spinal cord showing different sites oflesions used in the study of the contributions of different neural sub-systems to gait
  21. 21. 12.8- Hip, knee, & ankle trajectories of the swing limbobserved in response to a trip during early swing phase of walking, showing the elevation strategy. Normal stride= solid line, perturbed trial= dashed, arrow= contact of foot w/ obstacle, vertical solid line= normal heel contact, dashed= perturbed heel contact
  22. 22. • Type of strategy depends on where in swing phase trip occurs• Early- elevating strategy of the swing limb w/ muscle responses occurring @ 60 to 140 msec• Shows the increased flexion @ hip, knee, & ankle after obstacle contact compared w/ control trial• Elevating strategy- flexor torque component of the swing limb, w/ the temporal sequencing of the swing limb biceps femoris occurring prior to the swing limb rectus femoris to remove the limb from the obstacle before accelerating the limb over it• An extensor torque component in the stance limb generated an early heel off to increase the height of the body
  23. 23. 12.9- hip, knee, & ankle trajectories of the swing limb observed in response to the late swing phase of walking, showing the lowering strategies
  24. 24. • Lowering strategy was used• Early plantar flexion of the ankle• Accomplished by inhibitory responses in the swing limb vastus lateralis & an excitatory response of the swing limb biceps femoris, resulting in a shortened step length
  25. 25. • Initiation of gait is really just a fall, and regaing one’s balance• Prior to movement, COP is just posterior to ankle and midway btw both feet• As movement beings, COP first makes posterior and laterally toward the swing limb and then shifts towards the stance limb• COP toward the stance limb occurs simultaneously w/ hip and knee flexion and ankle dorsifelxion as swing limb prepares for toe off. Then the COP moves toward the stance limb• Toe off swing limb occurs w/ COP shifting from lateral to forward• RTO is where COP is when the right toe is off the ground• RHS is COP when the right heel strikes
  26. 26. 13.2- stick figured taken from motionanalysis of one step cycle of walking in an infant vs. adult
  27. 27. • Locomotor pattern changes over the first 2 years of development• Synchronous pattern of joint movements in newborn stepping to a more adult like dissociated pattern of joint motion by the end of the 1st year• Heel strike begins to occur in the front of the body• Shows kinematics of neonatal vs adult stepping• Infant shows high levels of hip flexion• Neonate: high degree of synchronized activity (extensor muscle were active simultaneously & coactivation of agonist & antagonist muscles
  28. 28. 8.10- responses from one child during the emergence ofcoordinated muscle activity in the leg and trunk muscles in response to platform perturbances
  29. 29. • EMG responses from one child during the mergence of coordinated muscle activity in the leg & trunk muscles in response to a fall backward• 2-6 month before pull to stand behavior and beginning of pull to stand did not show coordinated muscle response organization in response to threats to balance• As behavior progressed--> showed directionally appropriate responses in ankle muscles, muscles in thigh segment were added, consistent distal-to-proximal sequence• Independent stance/walk: trunk muscles activated--> complete synergy
  30. 30. 9.5- graph showing COP trajectory from perturbationonset to 2 sec after the perturbations for young stableand unstable older adults. Arrow indicates perturbation onset
  31. 31. • Platform perturbation= efficient return to the COP to a stable positoin, whereas the stable & ustable older adults each showed more COP oscillation before coming to a stable position• Unstable group showing the largest excursion of the COP & increase time for the COP to come to stabilization• NO differences in peak COM displacements• Each group aimed @ keeping a low COM displacement & when it went beyond, older adults shifted strategies and took a step
  32. 32. 13.8- nine phases of prone progression & graphs foreach phase showing the ages at which the behaviorwas seen and percentage of children in which it was observed
  33. 33. • 9 phases that take infant from the prone position to creeping/crawling & span months from birth to 10 to 13 months• 1) low extremity flexion& extension in a primarily flexed position• 2) spinal extension begins and head control• 3) spinal extension continues cephalocaudally, reaching thoracic• 4 &5) propulsion movements & arms and legs• 6) creeping position• 7) disorganized attempts @ progression• 8 & 9) organized propulsion in the creeping position
  34. 34. 13.12- A--> stick figures taken from motion analysis of the movements of a young and an older adult responding to a forward slip at heel strike
  35. 35. • Adults were less stable after a slip--> when recovering adults tripped more as the advancing swing limb caught on the surface• Occurred 66% adults, 15% younger adults• Older- greater trunk hyperextension & higher arm elevation in response to the slip; backward extension of the trunk & raising 1 arm• Had earlier contralateral foot strike & shortened stride length--> more conservative balance strategy• Longer onset latencies & smaller magnitudes in the postural muscle activated in balance recovery (TA, rectus femoris, abs)• To compensate they showed longer muscle response burst--> duration & arms in recovery, longer coactivation• Midstance slip and heel strike response are the same size--> no adaptation b/c reduced response capacity
  36. 36. • A. effect of a motor, cognitive, and combined task on gait speed• Step length
  37. 37. 16.2 feedforward/feedback control experimentsfeedforward= arrows, feedback= occurs at impact
  38. 38. • A. initial input is feedforward (using vision), while final input is feedback (using somatosensory inputs from the arm/hand)• B. angular changes in the elbow and wrist and muscle responses (rectified surface electromyograms)
  39. 39. 16.3
  40. 40. • Velocity profiles & movement durations of a reach vary depending on the goal of the task• Grasp- movement duration of the reach was longer than to point & hit a target preparing to grasp• Acceleration phase of the reaching movement was much shorter than the deceleration phase, but hitting a target w/ the index finger• Acceleration phase was longer than deceleration phase w/ the subject hitting the target @ a relatively high velocity• Movement times were shorter for grasp and throw versus grasp and fit
  41. 41. 16.4- reaching and manual- estimation tasks, grasping- A, manual estimation- B, maximum grip aperature versus manual estimation size --> C
  42. 42. • Reached for a disk placed in the center of one of the 2 sets of circles (hypothesized dorsal stream) or manually estimate the size of a disk (hypothesized ventral stream)• Results: manually estimated disk size as different, although they are the same size• Grip size was scaled to actual target size rather than apparent size• 16.14C- difference in max grip and manual estimated for disk• Max grip was greater for large disks, though subjects reported they were identical in size• Ventral stream of projections to the temporal cortex play a major role in the perceptual identification of objects• Dorsal stream- parietal cortex mediates the required sensorimotor transformations for usually guided
  43. 43. 16.9- in A: solid= position, dotted=velocity, B: solid= 55 mm diameter, dotted= 2mm
  44. 44. • When reaching forward to grasp an object, shaping of hand for grasping occurs during transportation component of reach• The graph shows changes in velocity and grip size• The pre grasp is under visual control• Two categories of properties affecting the shape: intrinsic (object size, shape, texture) and extrinsic (objects orientation, distance from body)• Size of grip opening is proportional to size of object (seen in part B). Each increased 1 cm in object size is associated with a max grip size of 0.77 cm.• Fingers change with opening while thumb stays still• Increase arm= stretched fingers and distance btw thumb and fingers is largest during final slow approach phase• Increase relationship is not due to neural constraints but may be most efficient way to reach
  45. 45. 16.10- reach, grasp, and manipulation
  46. 46. • A. comparison of reaction time and the number of response alternatives available• RT increases nonlineraly with the number of response alternatives• Information processing model, three stages between stimulus input and movement output• RT during successive blocks of trials when responding to a predictable (a) versus a nonpredictable (b) stimulus• RT decreases with predictable condition and does not change with random stimuli
  47. 47. 17.4- hand paths used by one infant at 4 ages compared to adults
  48. 48. • Infant reaches are curved @ early ages & become straighter by 2-3 years (straightness ratio)• About 2 @ reach onset & decrease to 1.3 to 1.4 by 2-3 years• Still less straight than adults (1)• Increase of smoothness• Max hand speed during reach occurs closer to the beginning of reach w/ development being @ .35 to .5 and moving to .2 to .4 of the reach by 2-3 years• Average reaching speed does not increase during this time period
  49. 49. 17.6
  50. 50. • 5 year olds use highest level of bollistic patterns• 7 year olds use high levels of step tramp patterns• 9-11 year olds use highest level of ballistic patterns w/ smooth decelerations, indicationg primary use of visual feedback at end of movement• This may be due to increased use of proprioceptive feedback in 7 year olds and restriction of feedback control in the homing- in phase in older children--> result of increased efficiency of breaking system
  51. 51. 17.11- graph showing the relationship between movement time and the index of difficulty of a task, for four age groups of children
  52. 52. • The intercept of the line w/ the y-axis reflects the general efficiency of the motor system• The slope reflects the amount of info that can be processed per second by the motor system• Y-intercept decreases with age (increased efficiency)• Age improvements depend on task and are more evident in discrete versus serial movements
  53. 53. 17.14- grasp force traces from a young subject and onolder adult showing typical grasp force patterns whenlifting an object w/ nonslippery versus slippery surface
  54. 54. • Adults have a decrease in manual dexterity• Becomes apparent in tasks such as buttoning a shirt or tying shoelaces• Time to complete increases by 25-40%• 81+ year used grasp forces that were two times as large than young adults• They take longer to adapt to the final grasp force for the rayon
  55. 55. 18.2- a comparison of wrist path in a control vs asubject w/ cerebellar pathology moving is slow accurate and fast accurate conditions
  56. 56. • Control: slow accurate condition line is wrist trajectory solid dot is target circles are finger endpoint• Control: fast accurate condition• Cerebellar: slow accurate condition in regular and unnecessary wrist movement• Cerebellar: fast (no so) accurate condition much less consistency with wrist movement not accurate
  57. 57. 18.16- experimental setup foradaptation of a catching task
  58. 58. • Participant set-up, ball dropped and impact- displacement values are plotted• Control: catches a light ball, adapts within two trials to catching a heavy ball, first trial of light ball again and there is a large negative impact displacement• Cerebellar pathology: reduces a persons ability to adjust to novel loads through trial- and-error practice• Requires 22 trials to adapt to heavy ball• Has no negative impact displacement on first light ball again
  59. 59. 18.3- experimental method used to study multi joint coordination between the shoulder and elbow
  60. 60. • A vs D multijoint shoulder and elbow coordination with a free vs constrained shoulder• B & E control made few errors in either condition• Cerebellar pathology patients made large end-point errors in free condition• F but no so in the constrained condition