1. Posture and Body Mechanics
chapter 11
Posture and Body Mechanics

2. Posture = Relative alignment of body segments with one another
Good alignment: provides minimal stress to segments
Poor alignment: creates imbalances   stress  adaptations  efficiency
Static posture used as the defining reference in evaluations

3. Standing: Anterior View
Plumb line bisects the body into symmetrical segments.
Line bisects nose, mouth, sternum, umbilicus, and pubic bones.
Feet are equidistant from plumb line.
Palms face lateral thigh.
(continued)

4. Standing: Anterior View (continued)
Level right to left: earlobes, shoulders, fingertips, nipples, iliac crests, patellae, medial malleoli
Patellae: directed forward
Feet: directed forward or out slightly
Knees and ankles: in line with each other
Knees: straight
Symmetrical muscle development

5. Figure 11.1

6. Standing: Posterior View
Plumb line bisects head and runs over spinous processes
Level left to right: earlobes, shoulders, scapulae, hips, posterior superior iliac spine, gluteal fold, posterior knee creases, medial malleoli
Scapulae lie against rib cage: T2-T7
Calcaneus: straight with Achilles perpendicular to floor
Symmetrical muscles
Weight equally distributed

7. Figure 11.2

8. Standing: Lateral View
Plumb line is slightly forward of lateral malleolus.
Line passes through external auditory meatus, earlobe, bodies of cervical spine, center of shoulder joint, and greater trochanter.
Line passes midway between back and chest, back and abdomen.
Line runs slightly posterior to hip joint, slightly anterior to knee joint (behind patella).
(continued)

9. Standing: Lateral View (continued)
Horizontal line between ASIS (anterior superior iliac spine) and PSIS (posterior superior iliac spine)
Weight balanced between heel and toes
Knees straight but not locked
Chin slightly tucked
Chest up and forward
Mild curve inward at cervical and lumbar spine

10. Figure 11.3

11. Sitting Posture
Seat height: allows feet flat on floor—90° at hips, 90° at knees
Seat depth: front edge 1 to 2 in. from posterior knee
Back height: to lower scapulae and support lumbar spine, thoracic spine
Arms: allow shoulder relaxation and permit forearms to rest with elbows 90°

12. Figure 11.4

13. Sitting Posture at Desk
Chair height: allows forearms to rest on desk with relaxed shoulders
At keyboard: elbows at 90° or slightly more, wrists in neutral, fingers able to rest on keyboard
NOT: forward head, rounded shoulders, flat lumbar spine, excessively curved thoracic spine, hyperextended wrists

14. Effects of Bad Posture
Slow changes over time: adaptation to stresses applied
Shortening of some structures, lengthening of opposing structures
Secondary weakness of both shortened and lengthened structures (length–tension relationship)

15. Length–Tension Relationship
As a muscle either shortens from or lengthens beyond optimal length, strength decreases.

16. Results Efficiency of movement is impaired.
Stress on specific segments during sport activities increases.
Muscles must work harder to maintain posture, increasing fatigue.
Individual becomes susceptible to injury.
Injury may become exaggerated with increased stresses already in place.

17. Pathological Alignments
Pelvis
Spine segments
Lower extremity
Upper extremity

18. Figure 11.5

19. Figure 11.6

20. Figure 11.7

21. Figure 11.8

22. Figure 11.9

23. Figure 11.10

24. Figure 11.11

25. Figure 11.12a

26. Figure 11.12b 26

27. Figure 11.12c 27

28. Figure 11.13

29. Figure 11.14a

30. Figure 11.14b 30

31. Figure 11.14c 31

32. Figure 11.15

33. Figure 11.16

34. Figure 11.17

35. Figure 11.18

36. Figure 11.19a

37. Figure 11.19b

38. Figure 11.20

39. Figure 11.21

40. Figure 11.22a

41. Figure 11.22b 41

42. Figure 11.22c 42

43. Figure 11.23

44. Other Considerations Regarding Malalignment
Sports increase postural deviations.
Anterior muscles are exercised more than posterior muscles
Unilateral activities
Age increases deviations.
Joint hyper- or hypo-mobility  muscle stresses.
Scar tissue from injuries can cause imbalances.
Site of pain may not be site of problem.

45. Body Mechanics
= The way the body is positioned and used during activity.
Correct mechanics makes the most effective use of the body’s forces and levers.
Incorrect mechanics leads to inefficient use and increases stress on the body segments.

46. Basic Principles Spine should remain straight.
Pelvis remains in neutral.
Lowering center of gravity increases stability.
Broadening base of support increases stability.
Feet are placed in direction of force application or acceptance.
Trunk strength is vital for force transmission, transfer, and body support.

47. Figure 11.25

48. Figure 11.26a

49. Figure 11.26b 49

50. Figure 11.26c 50

51. Figure 11.27

52. Figure 11.28

53. Figure 11.29

54. Figure 11.32