Biomechanics Part of Ergonomics Etymology Ergon (): work Nomos (): - - PowerPoint PPT Presentation
Biomechanics Part of Ergonomics Etymology Ergon (): work Nomos (): law Definitions The scientific study of the efficiency of man in his working environment. ( OED) ... a science whose main
– Ergon (ἔργον): work – Nomos (νόμος): law
– “The scientific study of the efficiency of man in his
working environment.” (OED)
– “... a science whose main purpose is to design
workspaces and tools that help people do their jobs and use their tools and other products comfortably and safely.” (Oregon OSHA)
3
motion, especially
– Low back (e.g., related to manual material handling) – Upper extremities (e.g., related to typing, assembly)
– 70 million physician office visits annually – 130 million total health care encounters
– Potential for long-term disability (but most return to work within 31 days) – Annual cost: $45 - $54 billion
1National Research Council (2001). Musculoskeletal Disorders and the Workplace: Low Back and Upper
Extremities, Washington: National Academies Press.
4
– exceptions: large hand forces, body movement
5
6
Source (Left): Wikimedia Commons, http://en.wikipedia.org/wiki/File:Human_skeleton_front_en.svg, accessed 19 Jan 10. Source (Right): Wikimedia Commons, http://en.wikipedia.org/wiki/File:Human_skeleton_back_en.svg, accessed 19 Jan 10.
7
Source (Left): Wikimedia Commons, http://en.wikipedia.org/wiki/File:Illu_vertebral_column.jpg, accessed 19 Jan 10. Source (Right): Konz & Johnson, Work Design, 6th edition.
8
Source: Wikimedia Commons, http://en.wikipedia.org/wiki/File:ACDF_oblique_annotated_english.png, accessed 19 Jan 10.
9
– Small bony joints covered with soft tissue that help
movement and keep structure.
10
(cervical vertebra)
Source: Wikimedia Commons, http://en.wikipedia.org/wiki/File:Cervical_vertebra_english.png, accessed 19 Jan 10.
11
– 2nd most common neurological problem in US* – 75,000,000 Americans have back problems – 6,500,000 Americans in bed each day with back pain – 80% working adults develop back pain during career – $7,400 per back claim – $50 billion/year spent in treatment*
– Low-back pain – Low-back impairment: reduced ability – Low-back disability: lost time due to injury – Low-back compensation: reimbursement for medical expenses,
lost wages
* Healthline (http://www.healthline.com) / National Institute of Neurological Disorders and Stroke
12
– Strains: muscles, ligaments stretched, torn from over-
activity
– Disc injury: herniated disc, ruptured disc compresses
nerve root, causes pain; usually lasts more than 72 hrs
– Sciatica: compression of sciatic nerve, pain in legs feet – Spinal Stenosis: narrowing of spaces in spin due to disc
degeneration, usually due to aging
– Other Causes
* Healthline (http://www.healthline.com)
13
14
15
– Weight – Physique – Gender
– Depression – Anxiety – Job dissatisfaction
– Posture – Speed – Repetition
– Workplace design – Slippery floors – Distractions
16
– Age [+] – Gender [x] – Body size [x] – Physical fitness [x] – Lumbar mobility [x] – Strength [x] – Medical history [+] – Years of employment [x] – Smoking [+/-] – Psychosocial [+] – Structural abnormalities [+]
– Heavy physical work [+] – Lifting [+] – Bending, stretching,
reaching [+]
– Twisting [+] – Pushing and pulling [+] – Prolonged sitting, standing
[+]
– Accidents [+] – Whole body vibration [+]
17
– reduce manual materials handling (MMH) – decrease weight – use 2 or more people where possible – Push or pull vs. lift & carry – minimize carrying distance – stacking height < shoulder height
18
– heavy objects at knuckle height – reduce lifting frequency – provide rest periods – use job rotation – provide handles
19
– Rank alternatives – Identify and correct problems – Not to rate absolute risk
– Biomechanical: ≤ 350 kg on L5-S1 – Physiological: ≤ 9.5 kcal/min
20
21
RWL = LC × HM × VM × DM × FM × AM × CM
22
– BIL = Body interference limit – H = Horizontal location – Large HM (small H) better (load close to body)
– VC = Vertical constant = 0.0075 in. – V = Vertical location – KH = Knuckle height (for typical lifter = 30 in.) – Large VM (V close to KH) better (load closer to optimal
lifting height)
23
– DC = Distance constant = 1.8 in. – D = Vertical travel distance
24
– Short = .001 h to ≤ 1 h with recovery time of ≥ 1.2 ×
duration
– Moderate = >1 h ≤ 2 h with recovery time of ≥ .3 ×
duration
– Long = >2 h but ≤ 8 h
25
– A = Angle of symmetry (≤ 135°) – 30% penalty for 90° angle
– See Table 11.3
– Height of initial and final hand–container coupling – Whether coupling is good, fair, or poor
26
27
28
29
http://www.cdc.gov/niosh/docs/94-110/pdfs/94-110.pdf
31
Source: Wikimedia Commons, http://en.wikipedia.org/wiki/File:Human_arm_bones_diagram.svg, accessed 19 Jan 10.
Notes: Skeleton is facing observer. Skeleton's left hand (on observer's right) is supinated (palm toward observer). Skeleton's right hand (on observer's left) is pronated (back toward
32
Source: Wikimedia Commons, http://en.wikipedia.org/wiki/File:Gray422.png, accessed 19 Jan 10.
33
– irritation & swelling of tendons
– inflammation of tendons & sheaths
– compression of median nerve caused by
– finger cannot be extended
– loss of circulation, numbness caused by
34
NIOSH (1997). Musculoskeletal Disorders and Workplace Factors, Cincinnati, OH: Author. http://www.cdc.gov/niosh/docs/97-141/pdfs/97-141.pdf
–
Repetition
–
Force
–
Hand/wrist vibration
–
Combinations of risk factors
–
Awkward (non-neutral) postures
–
High work demand (e.g., pace)
–
Cold
–
Direct pressure on nervers
–
Poor physical condition
–
Individual variability
35
36
38
– power grip: 38 mm - 50 mm diameter – precision grip: > 6 mm diameter.
– rotation undesirable: provide tab – rotation OK: round
– change in shape
39
– reduced slippage – reduced vibration
– resistance to heat/cold – resistance to electric shock/electrocution
– reduced compression, trauma
40
– use both hands – use feet
– change worker/work position – change tool (angled handles) – provide splints
– amount – duration – use large muscle groups (e.g., by trigger strip)
41
42
43
44
Source: Intercodev, http://www.intercodev.com/knives.htm, last accessed 19 May 04
45
Source: Intercodev, http://www.intercodev.com/knives.htm, last accessed 19 May 04
46
Source: Intercodev, http://www.intercodev.com/knives.htm, last accessed 19 May 04
47
Source: Wiha Quality Tools, http://www.wihatools.com/300seri/328_inomic.htm, last accessed 16 Nov 09
48
Source: MichaelHoligan.com, http://www.michaelholigan.com/Shopping/Product.asp?pfid=CHA957, last accessed 19 May 04
49
Source: Intercodev, http://www.intercodev.com/scissors.htm, last accessed 19 May 04
50
Source: Intercodev, http://www.intercodev.com/scissors.htm, last accessed 19 May 04
51
Source: Intercodev, http://www.intercodev.com/handles.htm, last accessed 19 May 04
52
Source: ContractorsTools.com, http://www.contractorstools.com/barco.html, last accessed 19 May 04
53
Source:NIOSH/Ergonomic Interventions in Ship Building/Coiled Hammer Handle, http://www.cdc.gov/niosh/ergship/coilhamm.html last accessed 19 May 04
54
–
http://vendorweb.humantech.com/
–
http://www.cdc.gov/niosh/docs/2004-164/pdfs/2004-164.pdf