Body Strength and Load Handling - PowerPoint PPT Presentation

Loading...

PPT – Body Strength and Load Handling PowerPoint presentation | free to download - id: 54f25-MThiZ



Loading


The Adobe Flash plugin is needed to view this content

Get the plugin now

View by Category
About This Presentation
Title:

Body Strength and Load Handling

Description:

Psychophysical (Liberty Mutual Tables) ... Recommended weight limit (RWL) is load constant multiplied by various factors. ... Height of initial/final hand ... – PowerPoint PPT presentation

Number of Views:180
Avg rating:3.0/5.0
Slides: 35
Provided by: kelly68
Learn more at: http://www.hpcnet.org
Category:

less

Write a Comment
User Comments (0)
Transcript and Presenter's Notes

Title: Body Strength and Load Handling


1
Body Strength and Load Handling
  • IENG 321
  • SDSMT
  • Spring 2009

2
Manual handling is a hot topic because…
  • 27 of all industrial injuries
  • 670,000 injuries/yr in the United States
  • 60 of all money spent on industrial injuries
  • 93,000,000 lost workdays/yr

3
Approaches to Recommendations
  • Biomechanical
  • Forces and torques
  • Esp. L4/L5 and L5/S1
  • Permitted load does not vary with frequency
  • Psychophysical (Liberty Mutual Tables)
  • Controlled setting MH tasks estimating population
    capabilities
  • By virtue, combines biomechanical and
    physiological stress
  • Physiological
  • Energy requirements of tasks and effect to
    cardiovascular system
  • Greater for occasional or frequent lifting?

4
Strength Factors
  • Individual
  • Related to gender, age, training, fitness
  • Muscle cross-sectional area
  • Length of muscle
  • Static or dynamic exertion
  • Fatigue
  • Neurophysiological excitation
  • Situational
  • The amount of strength one will or can apply
  • Motivation, ego, will to succeed, fear of injury
  • Skill/experience
  • Body motion
  • Ability to brace
  • Posture
  • Body segments used
  • Coupling

5
Strength Exertion
  • Static (Isometric)
  • Controllable, easy to measure
  • Rapid onset of fatigue
  • Reasonably estimate slow motion
  • Dynamic
  • More difficult to measure
  • More common
  • Isoinertial testing
  • Maximal
  • Structural integrity of object (safety factor)
  • gt 95th percentils
  • Minimal
  • Ability to perform task
  • 5th percentile

6
Strength Exertion
7
Hand Strength
  • Grasping, holding, pressing, pushing, pulling,…
  • Extrinsic Muscles
  • Muscles in forearms, tendons cross carpal
    ligament
  • Mostly gross motor control
  • Intrinsic Muscles
  • Muscles and tendons strictly in hand
  • Mostly fine motor control

8
Hand Strength
9
Hand Strength
10
Grips and Grasps
11
Hand Tool Design
  • Provide friction
  • Gloves may help, but generally increase required
    grip strength
  • Mechanical interlocking
  • Keep wrist straight
  • Natural grasp centerline 60o-70o
  • May need to supply left hand specific tooling
  • 10 population left handed

http//cdc.gov/niosh/docs/2004-164/default.html ht
tp//cdc.gov/niosh/pdfs/95-114.pdf
12
Whole Body Strength
  • Pushing
  • Pulling
  • Lifting
  • Lowering

13
Foot Strength
  • Standing
  • Little force
  • Infrequent operation
  • Support body weight on one foot
  • Alternating feet can help maintain muscle pump
  • Sitting
  • Exert large force with sufficient support

14
Pushing/Pulling Factors
  • Handles
  • Poor hand/handle surface is the weakest link
  • One hand vs. two hands
  • Postural freedom vs. fatigue
  • Body posture
  • Standing vs. sitting vs. kneeling
  • Application height
  • Where to push or pull from?
  • Direction
  • Generally perpendicular to shoulders

15
Push/Pull Summary
  • Two hands are usually better than one.
  • Force capability goes down as it is exerted more
    often.
  • Initial force capability is higher than sustained
    capability.
  • Pushing capability is higher than pulling.
  • Push at waist level pull at thigh level.

16
Task Modifications
  • Measure the force required to move all wheeled
    equipment periodically check the forces.
  • Force gauges
  • Install vertical push/pull bars on carts.
  • Push rather than pull loads.
  • Spinal compressive loads
  • Other safety concerns?
  • Avoid muscle-powered pushing and pulling for
    ramps, long distances, and frequent moves.
  • Use mechanical aids and momentum.
  • Reduce horizontal transfer force by reducing
    friction (rolling contact).

17
Holding
  • Problems
  • Holding gives a static load combining body weight
    and object weight.
  • Low-back pain arises from spine biomechanics.
  • Solutions
  • Reduce the magnitude and duration of the torque.
  • Use balancers.
  • Limit high loads to short durations.

18
Carrying
  • Replace carrying with pushing or pulling.
  • Minimize the moment arm of the load relative to
    the spine.
  • Consider carrying large loads occasionally rather
    than light loads often.
  • Use teamwork (common in medical facilities).
  • Consider using balancers, manipulators,
    conveyors, or robots.
  • Reduce lifting by raising the initial location.
  • Avoid carrying objects up and down stairs.
  • See Liberty Mutual Tables

19
NIOSH Lifting Guidelines
  • 51 lbs is the maximum that can be lifted or
    lowered (load constant).
  • Recommended weight limit (RWL) is load constant
    multiplied by various factors.
  • Weight 90 of U.S. industrial workers can safely
    lift
  • Lifting index load weight/RWL
  • Applicable when conditions are met!!

20
Basic NIOSH Lifting Formula
  • RWL LC HM VM DM FM AM CM
  • LC Load constant (51 lbs)
  • HM Horizontal multiplier
  • VM Vertical multiplier
  • DM Distance multiplier
  • FM Frequency multiplier
  • AM Asymmetry multiplier
  • CM Coupling multiplier

21
Multiplier Formulas
  • Horizontal multiplier
  • HM BIL H
  • BIL Body interference limit (10 in.)
  • H Horizontal location
  • Maximum 25 in. (functional reach)
  • Measured midpoint of hand to midpoint of line
    connecting ankles
  • Estimated Consider vertical location from floor
    and width of container
  • lt 10 in. 10 W/2
  • gt 10 in. 8 W/2

22
Multiplier Formulas
  • Vertical multiplier
  • Significant control at origin only?
  • Determines if destination of hands required.
  • VM 1 VC V KH
  • VC Vertical constant (.0075 in.)
  • V Initial vertical location of knuckles
  • Maximum 70 in.
  • KH Knuckle height of typical lifter (30 in.)
  • lt30 in. whole body lift
  • gt30 in. upper body lift

23
Multiplier Formulas
  • Distance multiplier
  • DM .82 DC D
  • DC Distance constant (1.8 in.)
  • D Absolute value of vertical travel distance
  • Asymmetry multiplier
  • AM 1 .0032 A
  • A Angle of symmetry

24
Multiplier Formulas
  • Frequency multiplier
  • See Table 13.9.
  • Lifting frequency mean number of lifts in a
    15-minute period
  • Lifting duration /session in hours may be
  • Short .001 h to 1 h with recovery time of
    1.2 duration
  • Moderate gt1 h 2 h with recovery time of .3
    duration
  • Long gt2 h but 8 h

25
(No Transcript)
26
Multiplier Formulas
  • Coupling multiplier
  • Depends on
  • Height of initial/final hand location and
    container coupling
  • Whether coupling is good, fair, or poor (see
    Table 13.11 or NIOSH guide for classification)

27
(No Transcript)
28
Example
  • Load Weight 15 lb
  • Ho 12 in
  • Vo 33 in
  • Hf 12 in
  • Vf 22 in
  • Ao 5o
  • Af 6o
  • Frequency .5 lifts/min
  • Duration 3 h
  • Recovery Time 6 hours
  • Questions
  • What does this assume about control of the object
  • Is the recovery time a necessary piece of
    information to determine the FM?
  • What is the RWL(s) and LI(s)?
  • How does this relate to the Liberty Mutual Tables?

29
Back Problems
  • Wear and tear worse than muscle strain
  • Low Back Pain (LBP)
  • Reduces mobility and vitality
  • Long absences from work
  • Current main cause of early disability
  • Major At Risk Jobs
  • Nurses
  • Laborers
  • Farmers
  • Baggage handlers
  • Warehouse workers

30
Intervertebral Disc Strain
31
Basic Biomechanics
32
Intra-abdominal Pressure (IAP)
  • Increase in pressure of abdominal cavity with
    contraction of abdominal muscles
  • Helps stabilize trunk
  • Reduces spinal loading
  • Back Belts
  • Thought to increase IAP and minimize risk of
    injury

33
Safe Manual Handling
  • Material handling aids
  • Proper techniques
  • We will visit this again in Workstation Design

34
Guidelines for Manual Handling
  • Bend the knees.
  • Dont slip or jerk.
  • Dont twist during the move.
  • Use machines.
  • Move small weights often.
  • Get a good grip.
  • Put a compact load in a convenient container.
  • Keep the load close to the body.
  • Work at knuckle height.
About PowerShow.com