Target the Problem,
Not the Symptom
Choosing The Correct
Ergonomic Analysis Tool
What We Are Going To Cover
General overview of different types of
ergonomic assessments
• Ergonomic Risk Assessment
– Ergonomic Risk Factors
– Qualitative Analysis
– Quantitative Analysis
• Physical Demand Assessment
– Post-offer testing for new hires
– Return-to-work
www.ergomethods.com
Ask the Following Questions
Before Analyzing the Job
•
•
•
•
Why are you analyzing the job?
How are you going to apply the data?
What are your desired outcomes?
Are you comparing apples to apples?
Physical Demand Assessment
vs.
Ergonomic Risk Assessment
• Ergonomic Risk Assessment
• Used to Assess Ergonomic Risks or Resolve
Ergonomic Risks
• Physical Demand Assessment
• Used for Post-Offer Testing, Functional
Capacity Evaluations & Return to Work
• Why Do We Have to Differentiate?
• Desired Outcome
• Liability and Legal Issues
Ergonomic Risk Assessments
The goal of an ergonomic risk assessment
is to identify factors that may increase the
likelihood of a worker developing a
musculoskeletal disorder (MSD).
Awkward Postures
Excessive Force
Personal
Repetitive Motions
MSD Risk
Factors
Contact Stress
Static Postures
Risk Depends On Magnitude,
Frequency and Duration
Ergonomic Risk
Assessments
•
•
•
•
•
•
•
•
•
RULA
REBA
Moore-Garg Strain Index
NIOSH Lift Equation
Back Force Estimation
Shoulder Force Estimation
Heart Rate
Rodgers Muscle Fatigue
Ergonomic Risk Assessment
Qualitative vs. Quantitative
• Qualitative
• Exploratory and/or investigative.
• Findings are not conclusive.
• Used to categorize
• Quantitative
• Used to recommend a final course of action.
Risk
Qualitative
Quantitative
Force
High Force
65 lbs
Repetition
Fast Pace
10 reps/1 min cycle
Posture
45 – 90 deg
45 Degrees of Flexion
Outcome
7/10 Rank
Force, Repetition, Posture Data
Rapid Upper Limb Assessment
• Rapid Upper Limb Assessment or
RULA is used to assess posture force
and movement associated with tasks
where the worker is seated or standing
without moving about.
• Qualitative assessment
Rapid Upper Limb Assessment
RULA Outcomes
• Qualitative
Assessment
• Compare to
other jobs
• Rank body
parts
4
Rapid Entire Body Assessment
• The Rapid Entire Body Assessment is
used to assess static, rapidly changing
and unstable postures.
• It can be used to assess handling loads.
• Qualitative assessment
Rapid Entire Body Assessment
Moore – Garg Strain Index
• The strain index (SI) is a method of
evaluating jobs to determine if they
expose workers to increased risk of
developing MSDs of the distal upper
extremity (i.e. elbow, forearm, wrist & hands)
• Based off of physiological,
biomechanical & epidemiological
principles.
• Validity has been demonstrated in pork
and poultry processing
Moore – Garg Strain Index
• Advantages
– Accounts for task duration &
recovery time
– Assesses adverse effects of
magnitude, duration & frequency
• Disadvantages
– Requires individuals with experience
& training
– Helpful to utilize video tape for
analysis
NIOSH Lifting Equation
•The NIOSH Lifting Equation is intended
for two-handed lifts with
without sudden changes in acceleration
that are performed from a standing
position.
•Based on biomechanical, physiological
and psychophysical criteria.
•The end product of the equation is the
RWL or Recommended Weight Limit and
the Lifting Index.
Variables
RWL = 51 X HM X VM X DM X AM X FM X CM
•
•
•
•
•
•
HM – Horizontal Multiplier
VM – Vertical Location Multiplier
DM – Vertical Distance Multiplier
AM – Asymmetry Angle (Twisting) Multiplier
FM – Frequency Multiplier
CM – Coupling Classification
V
VM
0
.78
5
.81
10
.85
15
.89
20
.93
25
.96
30
1.00
35
.96
40
.93
45
.89
50
.85
55
.81
60
.78
65
.74
70
.70
>70
.00
Vertical Multiplier
Variables
RWL = 51 X HM X VM X DM X AM X FM X CM
•
•
•
•
•
•
HM – Horizontal Multiplier
VM – Vertical Location Multiplier
DM – Vertical Distance Multiplier
AM – Asymmetry Angle (Twisting) Multiplier
FM – Frequency Multiplier
CM – Coupling Classification
Interpretation of Results
• The Recommended Weight Limit is
defined as the weight of the load in
which nearly all healthy workers could
perform over a substantial period of
time without an increased risk of
developing lifting-related low back
pain.
Interpretation of Results
• Lift Index = (Actual Load) / RWL
• Most experts believe that there will be an
increased risk of low-back injury for most (if
not all) workers if the lift index exceeds 1.
• Some experts feel that if workers are
properly screened (based on the task
requirements) and trained that they can
safely work at lift indexes greater than 1 but
less than 3.
Low Back Compressive Force Model
• Developed by Don Bloswick, PhD
(Professor at University of Utah)
• Used only as an estimation of low
back compressive force.
• Applicable lifting situations:
•Two handed lifts
•Smooth lifting situations without
sudden changes in acceleration
•Performed from a standing
position
Low Back Compressive Force Model
A = 3(BW)Cosθ
B = 0.5(L + HB)
C = 0.8[(BW)/2 + L] – 0.8
FC = A + B + C
Low Back Compressive Force Model
•BW: Body Weight
•L: Load
•HD: Horizontal Distance
•Cos Θ: Back Angle
FC = A + B + C
A = 3(BW)Cosθ
B = 0.5(L + HD)
C = 0.8[(BW)/2 + L] – 0.8
•FC: Total Compressive Force Estimate
•A: Back muscle force reacting to upper body weight
•B: Back muscle force reacting to the load moment
•C: Direct compressive component reacting to upper
body weight and the load
Low Back Compressive Force Model
Measure
Body Weight [kg]
Average body weight for an even gender distribution is 75 kg
Load [kg]
Horizontal Distance [m]
Hands to lower back {L5 - S1 Joint}
Back Posture (Angle from Vertical)
Θ
Load = L
Muscle
Force
UBW = 0.5 BW
HB
Symbol
Value
BW
200
L
35.0
HB
15
θ
45
Sin θ
0.71
[lb]
[lb]
[in]
[°]
[--]
Low Back Compressive Force Model
Outcomes
Contributor
Back Posture
A = 3 (BW) sin θ
Load Moment
B = 0.5 (L*HB)
Direct Compression
C = 0.8 [(BW)/2 + L]
Estimated Compressive Force
Fc = A + B + C
Value [lbf]
Computation
3*(
200
) * (
0.71
)
424
0.5 * (
35.0
) * (
15.00 )
263
0.8 * {(
200
)/2 + (
35.0
115
Comparison Value: 700 lbf
)}
802
Utah Shoulder Moment Estimation
• Developed by Don Bloswick, PhD
(Professor at University of Utah)
• Used only as an estimation of
shoulder moment force.
• Applicable when the arm is raised or
lowered without sudden changes in
acceleration
Utah Shoulder Moment Estimation
Variable and Abbreviations
• BW = Body weight in
lbs.
• D = Horizontal distance
from the load to the
should joint.
• L = Load weight in lbs.
• A = Forearm angle in
degrees
• B= Upper arm angel in
degrees
A
B
D
Utah Shoulder Moment Estimation
Mb = Moment at the shoulder due to the
weight of the arm.
Mf = Moment at the shoulder due to the
weight of the load in the hands.
Mtask = Total moment at the shoulder.
Mcap = Moment capacity
•
•
•
•
Mb = 0.0115 x D x BW
Mf = 0.5 x D x L
Mt = Mb + Mf
% Max = Mtask / Mcap
Utah Shoulder Moment Estimation
% Max = Mtask / Mcap
Forearm
angle (A)
45
Upperarm
angle (B)
90
135
180
50%
Male
0
632
691
751
810
45
598
658
717
777
90
565
624
684
743
135
531
591
650
710
180
498
557
617
676
Heart Rate
• Heart rate is the most convenient
physiological measure of job stress.
• In many situation heart rate is closely
related to maximum aerobic capacity.
• This data is very easy to gather with
today’s technology.
Heart Rate
Shift Heart Rate
Work Classification
< 90 bpm
Light Work
91-100 bpm
Moderate Work
101-120 bpm
Heavy Work
> 120 bpm
Very Heavy Work
Heart Rate
• Obviously this upper range could not be
sustained for long periods of time.
• A work capacity level of 33 percent for an
eight-hour work shift has long been the
accepted guideline for jobs where wholebody fatigue is primary concern.
• Longer work shifts also necessitate a lower
work capacity requirement. The
recommended work capacity guideline drops
to 30.5 percent for a 10 hour shift and to 28
percent for a 12-hour shift3.
Rogers Muscle Fatigue Analysis
• Studies of physiological muscle fatigue
at different effort levels and holding
times provided the basis for this
assessment.
• Looks and muscular effort (static &
dynamic) in relation to recovery time.
• Variables include:
– Effort
– Duration
– Frequency
• Not appropriate if fatigue is not likely to
occur during the task.
Rogers Muscle Fatigue Analysis
Category Scores Grouped by Priority for Change in the Order
of Effort, Continuous Effort, Duration and Frequency
Low (L)
Moderate (M)
High (H)
Very High (VH)
111
123
223
323
112
132
313
331
113
213
321
332
211
222
322
4xx
121
231
x4x
212
232
xx4
311
312
122
131
221
Awkward Postures
Excessive Force
Personal
Repetitive Motions
MSD Risk
Factors
Contact Stress
Static Postures
Risk Depends On Magnitude,
Frequency and Duration
Wrist MSDs - Reps & Force
20
16.6
15
Odds
Ratio
10
5
2.9
1
2.7
0
Control
group
Force
Reps
Force +
Reps
Ergonomic Risk Assessments
The goal of an ergonomic
risk assessment is to
identify factors that may
increase the likelihood of
a worker developing a
musculoskeletal disorder
(MSD).
Standardized
Ergonomic
Risk
Assessment
Quantitative Assessment
Problem Solving:
The Problem Definition
The ___________ employees are
experiencing fatigue or
discomfort in ___________ due
to_________ .
Problem Solving Matrix
Physical Demands
• Physical Demands Analysis provides an
overview of physical, environmental and
psychosocial stressors within a particular
job classification or task.
Used in Functional Testing
Examples:
stoop, lift, push, pull, carry,
walk, climb, drive, sit, reach
forward, etc.
Physical
Demands
Physical
Demand
Photo Documentation
•Quick reference for job
requirements for:
•HR
•Physicians
•Therapists
Functional Testing Protocol
#
Required Test
Passing
1
Static Grip Strength Dominant (stop 1)
75 lbs
2
Static Grip Strength Non-Dominant (stop 1)
75 lbs
3
Lift 0 “ to 45”
55 lbs
4
Reaching Task Utilizing BTE ER
Completion of Test
5
Single Arm Lift (Right & Left Hands)
20 lbs
6
Lateral Pinch (Right & Left Hands)
15 lbs
7
Finger Press (Right & Left Hands)
25 lbs
8
Dynamic Push Shoulder Level
45 lbs
9
Dynamic Pull Shoulder Level
45 lbs
10
Simulated Work Task (Bolt Box) for 3 minutes
Completion of Task
11
Bilateral Carry
35 lbs
Functional
Testing
In Summary
• Physical Demand Assessments
• Functional Testing
– Used to document physical requirements of essential
job tasks
– Used for post-offer testing
– Used for return-to-work
• Ergonomic Risk Assessments
• Qualitative
– Used to give a quick “snapshot” of overall status
– Used to identify areas for more in depth analysis
– Used to compare and rank jobs
• Quantitative
– Used to quantify ergonomic risks
– Used to resolve ergonomic issues
– Used for before and after comparisons
Assessment Objectives
• Ergonomic Risk Assessments
• Reduce ergonomic risk factors and
prevent injuries from occurring
• Choose the correct analysis tool
• Quantify the ergonomic risks
• Physical Demand Assessments
• Hire individuals with the physical
capabilities to perform the job safely
• Test injured individuals to confirm
legitimacy of the injury claim and return
to work status.
Speaking From Experience
Make Sure:
• Ergonomists are certified by the BCPE
• Help you develop a process not a
program.
• Don’t just provide data but provide
solutions.
• Involve employees in the problem
solving process.
Other Ergonomic Assessments
•
•
•
•
•
•
•
•
Liberty Mutual Tables
ACGIH for Hand Activity Level
WISHA Hand-Arm Vibration Analysis
MSD Analysis Guide (MAG)
Time Motion Studies
Work Recovery Cycles
3D Static Strength Prediction Program
Biomechanical Analysis
Remember
• Your results are only as good as the
data used to calculate them.
• There are many ergonomic analysis
tools, make sure you choose tool and
an expert that will provide the data you
need for your desired outcome.
• Prove you’re success with numbers
and dollars.
ErgoMethods Has
One Objective
All employees
perform their job
without pain or
discomfort and that
all employees reach
their retirement in a
physical condition
that enables them to
enjoy it!
Mark A. Heidebrecht, MSE, ACSM, CEA
14610 S Kaw
Olathe, KS 66062
913-393-2773
mark@ergomethods.com
www.ergomethods.com