Understanding Biomechanics of Work and Musculoskeletal System

undefined
 
Biomechanics of Work
 
Chapter 11
 
NIOSH Report & Others
 
500,000 workers suffer overexertion injuries
each year
60 % involve lifting and lower back.
Compensation & indirect costs total $27 –
$56 Billion (1991).
10 % involve upper extremities (fingers,
hand, wrists, arms, & shoulders) due to
cumulative trauma disorders (1987)
 
Musculoskeletal System
 
Bones (206) & connective tissues
Tendons – fibrous connective tissues connecting muscles
to bones
Ligaments – fibrous tissues that keep articulate joints in
place
Cartilage – translucent elastic tissue
Fascia cover body structures separating one from another
Muscles (400) – composed of bunches of muscle
fibers, connective tissue, & nerves.
Only body tissue that can expand or contract when fired
by a nerve impulse.
Long cylindrical cells.
Force is dependent on cross section of bundle
 
Biomechanical Models
 
Fundamental Basis (Newton’s laws)
1.
Mass remains in uniform motion or at rest until
acted on by an unbalanced force.
2.
Force is proportional to the acceleration of a
mass
3.
Any action is opposed by reaction of equal
magnitude
Static equilibrium
Sum of all external forces on object equal zero
Sum of all external moments must equal zero
 
Single-Segment Planer,
Static Model
 
Single-Segment Planer,
Static Model (cont.)
 
W = mg
W  
is weight in newtons
m  
is mass in kilograms
g  
is gravitational constant (9.8 
m/s
2
)
W = 20kg X 9.8 m/s
2  
= 196 N
W
 
load on each hand 
= 98 N      
W 
forearm & hand  
 
= 16 N
(forces at elbow = 0) = - 16 N – 98 N + R 
elbow 
= 0
R 
elbow 
 = 114 N
moments at elbow = 0) = (- 16N) (.18 m) + (- 98N) (.36m) + 
M 
elbow 
 =
0
M 
elbow 
 = 38.16
 
Two-Segment Planer,
Static Model
 
Low Back Biomechanics
of Lifting
 
Low Back Biomechanics
of Lifting (cont.)
 
M 
load & torso
 
= 
W
 load
  
x 
h
 + 
W
 torso
 
 x 
b
Where:
h
 
 horizontal distance from load to L5/S1 disk
b – 
horizontal distance from center of mass of the torso to the L5/S1 disk
M
  back-muscle 
 
= 
F
 back-muscle  
x 5(N–cm)
moments
 
at L5/S1 disk = 0)
F
 back-muscle 
 
x 5 = 
W
 load
  
x 
h
 + 
W
 torso
 
 x 
b
F
 back-muscle 
= (
W
 load
  
x 
h
 + 
W
 torso
 
 x 
b
)/5
Assume 
h 
= 40 cm & 
b 
 = 20 cm then
F
 back-muscle 
= 8
W
 load
  
+ 4
W
 torso
Assume  
W
 load
  
=
 
 300 N or 30kg (75lb) & 
W
 torso
 
= 350 N (80lb) then
F
 back-muscle  
= 
3800 N or 388kg (855lb)
 
NIOSH Lifting Guide
 
RWL 
= 
LC  
x
 HM 
x
 VM 
x
 DM 
x
 AM 
x
 FM 
x
 Cm
 
NIOSH Lifting Guide (cont.)
 
RWL 
= 
LC  
x
 HM 
x
 VM 
x
 DM 
x
 AM 
x
 FM 
x
 Cm
 
NIOSH Lifting Guide Example
 
NIOSH Lifting Guide Example
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
LI = Lifting Index
 
Manual Materials Handling
 
Material Handling Devices (MHDs)
Located as close as possible to body
Located about thigh or waist high
Don’t locate large packages close to the
floor (30 inches optimum)
Minimize torso twist
Minimize frequent lifting per work period
 
Reducing Asymmetric Multiplier
 
Reducing Vertical & Horizontal
Multipliers
 
Seated Work Chair Design
 
Disk Pressure Measurements in
Standing & Unsupported Sitting
 
Common Forms of Cumulative
Trauma Disorders (CTDs)
 
Tendon-related – in repetitive work muscles
steel blood from tendons & inflammation
results
Neuritis – repetitive work in awkward
positions irritate & damage nerves
Ischemia – tingling/numbness caused by
lack of blood flow
Bursitis – inflammation of a bursa (sac
containing synovial or viscous fluid)
 
CTDs of Certain Joints of the
Extremities & Remedies
 
Finger – vibration-induced white fingers (Raynaud’s
syndrome)
Hand & Wrist – Carpal tunnel syndrome
Elbow – tennis elbow (lateral epicondylitis), golfer’s
elbow (medial epicondylitis) & telephone operator’s
elbow
Shoulder – Tasks requiring hands & arms above the
shoulder cause rotator-cuff irritation, swimmer’s
shoulder, or pitchers arm and can result in injury
Evaluate & redesign tasks that cause CTDs.
Understand that certain worker populations  are
more predisposed to these injuries
 
Wrist Bending Implications
 
Hand Tool Design
 
1.
Do not bend the wrist
2.
Shape tool handles to assist grip
3.
Provide adequate grip span
Accommodate sex differences
4.
Provide finger & glove clearances
Accommodate sex differences
 
Hand Tool Design
 
Grip Strength Male/Female
Slide Note
Embed
Share

Explore the biomechanics of work and musculoskeletal system in this comprehensive overview. Learn about the impact of overexertion injuries, NIOSH reports, and the structure and functions of the musculoskeletal system. Delve into biomechanical models, static and dynamic models, and the biomechanics of lifting, focusing on the low back. Gain insights into forces, moments, and equilibrium in biomechanics.


Uploaded on Jul 10, 2024 | 0 Views


Download Presentation

Please find below an Image/Link to download the presentation.

The content on the website is provided AS IS for your information and personal use only. It may not be sold, licensed, or shared on other websites without obtaining consent from the author. Download presentation by click this link. If you encounter any issues during the download, it is possible that the publisher has removed the file from their server.

E N D

Presentation Transcript


  1. Biomechanics of Work Chapter 11

  2. NIOSH Report & Others 500,000 workers suffer overexertion injuries each year 60 % involve lifting and lower back. Compensation & indirect costs total $27 $56 Billion (1991). 10 % involve upper extremities (fingers, hand, wrists, arms, & shoulders) due to cumulative trauma disorders (1987)

  3. Musculoskeletal System Bones (206) & connective tissues Tendons fibrous connective tissues connecting muscles to bones Ligaments fibrous tissues that keep articulate joints in place Cartilage translucent elastic tissue Fascia cover body structures separating one from another Muscles (400) composed of bunches of muscle fibers, connective tissue, & nerves. Only body tissue that can expand or contract when fired by a nerve impulse. Long cylindrical cells. Force is dependent on cross section of bundle

  4. Biomechanical Models Fundamental Basis (Newton s laws) 1. Mass remains in uniform motion or at rest until acted on by an unbalanced force. 2. Force is proportional to the acceleration of a mass 3. Any action is opposed by reaction of equal magnitude Static equilibrium Sum of all external forces on object equal zero Sum of all external moments must equal zero

  5. Single-Segment Planer, Static Model

  6. Single-Segment Planer, Static Model (cont.) W = mg W is weight in newtons m is mass in kilograms g is gravitational constant (9.8 m/s2) W = 20kg X 9.8 m/s2 = 196 N Wload on each hand = 98 N W forearm & hand = 16 N (forces at elbow = 0) = - 16 N 98 N + R elbow = 0 R elbow = 114 N (moments at elbow = 0) = (- 16N) (.18 m) + (- 98N) (.36m) + M elbow = 0 M elbow = 38.16

  7. Two-Segment Planer, Static Model

  8. Low Back Biomechanics of Lifting

  9. Low Back Biomechanics of Lifting (cont.) M load & torso= Wloadx h + Wtorsox b Where: h horizontal distance from load to L5/S1 disk b horizontal distance from center of mass of the torso to the L5/S1 disk Mback-muscle = Fback-muscle x 5(N cm) (moments at L5/S1 disk = 0) Fback-muscle x 5 = Wloadx h + Wtorsox b Fback-muscle = (Wloadx h + Wtorsox b)/5 Assume h = 40 cm & b = 20 cm then Fback-muscle = 8Wload+ 4Wtorso Assume Wload= 300 N or 30kg (75lb) & Wtorso= 350 N (80lb) then Fback-muscle = 3800 N or 388kg (855lb)

  10. NIOSH Lifting Guide RWL = LC x HM x VM x DM x AM x FM x Cm

  11. NIOSH Lifting Guide (cont.) RWL = LC x HM x VM x DM x AM x FM x Cm

  12. NIOSH Lifting Guide Example

  13. NIOSH Lifting Guide Example LI = Lifting Index

  14. Manual Materials Handling Material Handling Devices (MHDs) Located as close as possible to body Located about thigh or waist high Don t locate large packages close to the floor (30 inches optimum) Minimize torso twist Minimize frequent lifting per work period

  15. Reducing Asymmetric Multiplier

  16. Reducing Vertical & Horizontal Multipliers

  17. Seated Work Chair Design

  18. Disk Pressure Measurements in Standing & Unsupported Sitting

  19. Common Forms of Cumulative Trauma Disorders (CTDs) Tendon-related in repetitive work muscles steel blood from tendons & inflammation results Neuritis repetitive work in awkward positions irritate & damage nerves Ischemia tingling/numbness caused by lack of blood flow Bursitis inflammation of a bursa (sac containing synovial or viscous fluid)

  20. CTDs of Certain Joints of the Extremities & Remedies Finger vibration-induced white fingers (Raynaud s syndrome) Hand & Wrist Carpal tunnel syndrome Elbow tennis elbow (lateral epicondylitis), golfer s elbow (medial epicondylitis) & telephone operator s elbow Shoulder Tasks requiring hands & arms above the shoulder cause rotator-cuff irritation, swimmer s shoulder, or pitchers arm and can result in injury Evaluate & redesign tasks that cause CTDs. Understand that certain worker populations are more predisposed to these injuries

  21. Wrist Bending Implications

  22. Hand Tool Design 1. Do not bend the wrist 2. Shape tool handles to assist grip 3. Provide adequate grip span Accommodate sex differences 4. Provide finger & glove clearances Accommodate sex differences

  23. Hand Tool Design

  24. Grip Strength Male/Female

Related


More Related Content

giItT1WQy@!-/#giItT1WQy@!-/#giItT1WQy@!-/#giItT1WQy@!-/#giItT1WQy@!-/#