Transcript Anatomy and Biomechanics

Anatomy and Biomechanics
for Occupational Ergonomics
IE 665
Anatomical sites important for
occupational ergonomics
• Spine – Occupational back pain
• Upper extremity – CTDs in neck, shoulder
and wrist
• Lower extremity – pain foot and ankle
Lordosis
Kyphosis
•Spinal curves
•Spinal shrinkage and
•Disc nutrition
•No pain sensation in load
bearing bodies
•Micro-trauma of discs and
cumulative load
•Disc degeneration
Clavicle
Scapula
Humerus
Radius
Ulna
Phalanges
Carpals
Metacarpals
Rotor cuff syndrome
Tendonitis
Bursitis
Frozen shoulder
Ball and socket – Shoulder, Hip
Hinge – Elbow, Knee
Pivot – Between ulna and radius
Fixed - Skull
Bursa
A small, flat, fluid filled sack
protects ligaments from friction
with bones
Bursitis – inflamed bursa
All body segment is subjected to gravitational force
When CG of a body segment is vertically aligned with a joint – joint tension or
compression = weight of the body segment
Due to postural changes, CG of the body segment moves away from the
joint’s vertical alignment. This creates a moment around the joint.
M = Force*Moment arm (perpendicular distance from the joint axis).
This moment due to gravitational force is countered internally by the muscles
to maintain the posture.
To maintain the posture MR =MM
MR = Moment due to external forces
MM = Moment due to internal muscle forces
MR
MM
Head-neck – 7% of BW
=0.07*150 = 10.5 lb
Ratio of moment arm = 2:1
Muscle force = 21 lb
Joint compressive force = 31.5
lb

Body weight = 200 lb
R = Upper body wt = 200*0.65=
130 lb
F=back muscle tension at (L5/S1)
F
?
R
Spine compression at (L5/S1) ?
For straight back:
2”
8”
R*2=F*2 or, F = 130 lb
2”
2”
Total L5/S1 compression
= R+F = 260 lb
For bent back:
R*8=F*2, F= 130*8/2 = 520 lb
Total L5/S1 compression

R+F =520+130 = 650 lb
L5/S1 joint compression increased by 2.5 times and back
muscle tension increased by 4 times from leaning forward