Ergonomics: Back Injuries

1
Ergonomics Back Injuries
Dana Root, MS, PT, CPE OSHA Region V, Ergonomics
Coordinator dana.root_at_dol.gov 414-297-3315
2
Comparison of Total Injury and Illness Cases
Involving Days Away from Work to MSD Cases
Involving Days Away from Work, 1999-2004
Injuries and Illnesses (Thousands)

• Median Days Away
• 1999 7 days
• 2000 7 days
• 2001 8 days
• 2002 9 days
• 2003 10 days
• 2004 10 days

34
35
34
34
33
32
Source Bureau of Labor Statistics U.S.
Department of Labor Survey of Occupational
Injuries and Illnesses
Percentage of Total Cases that are MSD cases
3
Direct Costs of Ergonomic Injuries

• 2005 Liberty Mutual Workplace Safety Index
• Top 10 workplace injuries
• 1. Overexertion
• 26.4 of all injuries
• 13.4 BILLION nation-wide
• 6. Repetitive motion injuries
• 5.9 of all injuries
• 3.0 BILLION nation-wide

Source Liberty Mutual Research Institute Annual
Workplace Safety Index 2005
4
Direct Costs of Injuries

• Top cause of serious workplace injuries
• Overexertion 34
• Excessive exertion
• Lifting, lowering, pushing, pulling,
• holding, carrying, throwing
• Repetitive motion 13.5

Source Liberty Mutual Research Institute Annual
Workplace Safety Index 2005
5
Overexertion Injuries

• Preferred safety intervention
• Better training 16.6
• Better equipment and workspace 7.4

Source Liberty Mutual Research Institute Annual
Workplace Safety Index 2005
6
Overexertion and Low Back Pain

• Overexertion is the most common cause of back
  injuries
• Muscle strains and sprains
• Force is the most important risk factor
• Job physical factors
• Non-occupational risk factors may increase risk
• Individual issues
• Psychosocial issues

7
Overexertion Injury Claims Low Back Pain

• 67 involve lifting
• 20 involve pushing/pulling
• 87 are related to materials handling

8
Point You in the Right Direction
9
(No Transcript)
10
(No Transcript)
11
(No Transcript)
12
(No Transcript)
13
(No Transcript)
14
(No Transcript)
15
(No Transcript)
16
(No Transcript)
17
(No Transcript)
18
So, why is this important?
19
Third Class Lever Elbow
AFm
20
MAm 2
MAw 14
AFm
MAm
W
MAw



20

• AFm 20 14 / 2
• 140 pounds

21
Human Body is at a Mechanical Disadvantage

• Gains
• ? range of motion
• ? speed of movement
• Compressive force at the elbow
• 20 pounds 140 pounds 120 pounds

22
Third Class Lever Low Back
MAm 2
MAw 25
20
AFm
AFm MAm W MAw
AFm 20 25 / 2
250
23
Example

• Weight 50 pounds
• MAw 12 inches
• Body wt. 100 pounds
• MAbw 8 inches
• AFm ?
• MAm 2 inches

24
AFm MAm W MAw BW MAbw
Example
AFm (50 12) (100 8) / 2
1400/2 700 pounds
25
With Body Weight Without Body Weight

• Compressive Force
• 700 100 50 850pounds
• 300 50 350 pounds

• Applied Force
• 700 pounds
• 300 pounds

26
Body Weight is Primary Compressive Force

• NIOSH recommended limit is Fc ? 770
• Back muscles generate force ? if too much can
  cause injury
• Most of compressive force comes from body weight
• If load ?
• Muscles create ? compressive forces on the spine

27
Human Body is at a Mechanical Disadvantage

• Gains
• ? range of motion
• ? speed of movement
• Compressive force at the elbow
• 20 pounds 140 pounds 120 pounds

28
6 Task Variables

• Horizontal Distance
• Vertical Location
• Vertical Travel Distance
• Asymmetrical Angle
• Coupling
• Frequency

29
6 Task Variables

• Horizontal Position of Load
• Most significant influencing factor
• Affects compressive forces on the L5S1 disc
• Distance the hands are away form the mid-point
  between the ankles

30
(No Transcript)
31
RWL Recommended Weight Limit

• Load constant 51 pounds
• RWL LC HM VM DM AM FM CM

32
Lifting Index

• Relative estimate of the level of physical stress
  associated with the lifting task
• LI Load weight / RWL
• Lifting is the same as lowering

33
Lifting Lowering Control Options

• Body mechanics options
• If lift correctly can lift just about anything gt
  NO
• Compression
• Strength
• Energy expenditure
• Assumption can bring load close to the body
• Strongest position with hands between knees
• Moment arm small when hands by crotch

34
Lifting Lowering Control Options

• Engineering options
• Weight of object
• Knuckle and shoulder height
• Distance away from body horizontal location
• Origin/destination of lift
• Slid, push, pull

35
Pushing versus Pulling

• Force exerted by the body
• Type of wheels
• Types of bearings
• Type of surface
• Slope of surface
• Handle height

36
Pushing versus Pulling

• Force exerted by the body
• Pulling force
• Flex spine
• Back muscles contracting gt ? compressive forces

37
Pushing versus Pulling

• Force exerted by the body
• Pushing force
• Abdominal muscles are more active
• Less compressive force

38
Pushing versus Pulling

• Control options
• Keep forces low
• Initial and peak
• Handle height between hip and shoulder
• Large wheels
• To ? friction
• Slip resistant shoes
• Good housekeeping
• Good steering mechanism
• Incline surfaces lt 2?

39
Energy Expenditure

• Aerobic activities
• Produce whole body fatigue
• Fast paced lifting, lowering, walking, climbing
• Repetitive lifting gt overexertion injury
• Factors affecting aerobic capacity
• Gender
• Age
• Physical fitness
• Nature of work
• Whole body

40
Energy Expenditure Control Options

• Effect of the workload
• Lifts versus trips
• Fatigue versus spinal compression
• Lifting technique
• Efficiency
• Amount of work
• Endurance

• Work pace
• Heavier object
• Heavier body weight
• Lift versus lower
• Lower less energy
• Carrying location
• Center of gravity

41
Have We Accomplished Our Goal?

• What Is the Goal?
• Send Every Worker Home at the End of the Day
  in the Same Condition As When They Came to Work

42
Ergonomics Free Resources

• www.osha.gov
• www.cdc.gov/niosh
• www.nsc.org
• www.hfes.org
• www.ergoweb.com
• www.dir.ca.gov
• www.lni.wa.gov

43
Ergonomics More Free Resources

• NIOSH Elements of Ergonomics Programs, 97-117
• Easy Ergonomics A Practical Approach for
  Improving the Workplace
• Phone [phone]

44
ALWAYS THINK SAFETY BEFORE LIFTING A HEAVY LOAD
45
(No Transcript)