kinesiology_posture__physio_lecture-10.pdf
- 1. Posture Kinesiology RHS 341 Lecture 10 Dr. Einas Al-Eisa
- 2. Posture • = body alignment • = the relative arrangement of parts of the body • Changes with the positions and movements of the body throughout the day and throughout life
- 3. Good posture • “the state of muscular and skeletal balance which protects the supporting structures of the body against injury and progressive deformity” • “when the muscles function most efficiently” (The American Orthopedic Association, 1946)
- 4. Factors affecting posture • General health • Body build • Gender • Strength and endurance • Kinesthetic awareness • Personal habits • Demands of the work place • Social and cultural traditions
- 5. Posture description • Static (rest) posture = posture in rest or without anticipated action (e.g., lying, sitting, standing) • Dynamic posture = posture in action or in anticipation of action
- 6. Posture description • Efficiency of motion is determined by: ¾The posture maintained in the trunk ¾Positioning of the vertebral segments (stresses imposed upon the spine)
- 7. The spine (vertebral column) has to meet 2 functions Strength Mobility
- 10. Posture and life cycle • Infants’ ability to assume and maintain upright posture is limited because their postural reaction still needs to be perfected • Upright standing posture is inherently unstable because the body’s center of gravity is situated high above a relatively small base of support
- 12. Posture and life cycle • Spinal curvature: – In the neonate: the whole spine is flexed forming a “C” shaped curve (convex posteriorly) from the occiput to the sacrum – When the infant begins to lift his head: the cervical curve reverses to become convex anteriorly – As the toddler begins to sit and stand: the lumbar curve reverses like the cervical
- 15. Posture and life cycle Once the standing position is achieved, the spine has four curves: 1. Cervical curvature: convex anteriorly (secondary) 2. Thoracic curvature: convex posteriorly (primary) 3. Lumbar curvature: convex anteriorly (secondary) 4. Sacral curvature: convex posteriorly (primary)
- 16. Posture and life cycle • In old age: ¾the shape of the spine tends to revert back to the “C” shaped curve ¾spinal flexibility is greatly reduced ¾in some elderly, the cervical curve may increase as they try to keep their eyes directed parallel to the floor, so that they can look ahead
- 17. The seven ages of man
- 18. Abnormal posture • Lordosis = an increase in the anterior lumbar curve • Kyphosis = an increase in the posterior thoracic curve • Scoliosis = lateral curvature
- 20. Kyphosis
- 22. Abnormal posture • High heels shoes throw the body weight forward, so the spine may adapt by increasing the lumbar curvature (lordosis) • Scoliosis may affect the shape of the thorax, which may create problems in breathing
- 23. Abnormal posture • Degenerative changes in the spine due to disease or aging may lead to permanent deformity
- 24. Standing posture • To maintain upright standing posture, the “S” shaped spine acts as an elastic rod to support the weight
- 25. Standing posture • Since the center of gravity lies in front of the spine a continuous forward bending moment is imposed upon the trunk in standing the posterior muscles and ligaments must control and maintain the standing posture
- 26. Standing posture • Erect posture: activity in the erector spinae muscle (trunk extensors) • Slouched posture: the ligaments and joint capsules take most of the responsibility for maintaining the posture
- 27. Postural sway • Standing is not a static position: the upright position is maintained by the alternating action of various muscles to keep the body’s center of gravity over the base of support • The magnitude of sway (as determined by the path of the body’s line of gravity) tends to be larger in the very old and very young
- 28. Postural sway • Prevents fatigue (because of the alternating periods of activity and inactivity in the motor units) • Assist venous return
- 29. Postural sway • Affected by: ¾Vision ¾Ankle and foot proprioceptors
- 30. Standing posture • Postural sway in standing is controlled by: ¾The erector spinae muscles ¾The abdominal muscles ¾The psoas major • All of these muscles are slightly active in standing, with more activity in the thoracic region than the lumbar and cervical regions……….why?
- 31. Standing posture • The ideal standing posture is one in which the line of gravity runs: ¾Through the mastoid process ¾Just in front of the shoulder joint ¾Just behind the hip joint ¾Just in front of the center of the knee joint ¾In front of the ankle joint
- 32. Line of gravity
- 34. Standing posture • An ideal balanced posture reduces the work needed by the muscles to maintain the body in erect position
- 35. Standing posture • Muscles active in standing: ¾Soleus is continuously active because gravity tends to pull the body forward over the feet ¾Iliopsoas remains constantly active ¾Gluteus medius and tensor fascia lata are active to counteract lateral postural sway ¾Erector spinae muscles are active to counteract gravity’s tendency to pull the trunk forward
- 36. Sitting posture • Requires less energy expenditure and imposes less load on the lower limb than standing • But, prolonged sitting can have negative effects on the lumbar spine
- 37. Sitting posture • Unsupported sitting: high muscle activity in the thoracic region, with low levels of activity in the abdominals
- 38. Sitting posture • Unsupported sitting places more load on the lumbar spine because it creates: ¾a backward pelvic tilt ¾a flattening of the lower back ¾forward shift in the center of gravity places load on the discs and the posterior structures of the vertebral column (ligaments, capsules, muscles)
- 39. Sitting posture • Supported sitting: the load on the lumbar vertebrae is less than unsupported sitting
- 40. Sitting posture • Prolonged sitting in a flexed position may: ¾increase the resting length of the erector spinae muscles ¾overstretch the posterior ligamentous structures
- 41. Sitting posture • Ergonomic intervention: ¾Raising the height of the work station (to reduce flexion of the cervical and lumbar regions) ¾The use of foot rest (to relieve strain) ¾Symmetrical working position (to reduce the incidence of twisting which stretches the posterolateral structures, particularly the annulus)
- 42. Lifting • Lifting may result in a back injury as a result of: ¾the weight of the load ¾the distance of the load from the body
- 43. Identify the best lifting strategy and explain why?
- 46. Lifting • Proper lifting posture is one in which: ¾the back is erect ¾knees are bent ¾weight is close to the body ¾movement occurs through one plane only (avoid twisting)
- 47. Lifting • Stooped lifting posture reduces the activity in the trunk extensor so the forward moment is resisted by passive structures (discs, ligaments, fascia) placing these structures at risk of injury