Week 5 Lectures Flashcards
What is the relationship between injury risk, demand, and frequency/duty cycle
injury risk is proportional to task demand/ tissue capacity
at extreme demand, acute injury is likely
at extreme frequency/duty cycles, RSI likely
What are the major risk factors for MSIs
Force
Awkward posture
Repetition
Duration
Fatigue
Psychosocial
Hand-arm vibration
Identify measurement tools for force
How can we determine maximum force?
scale
dynamometer
pinch/power guages
EMG
pressure sensors
BORG scale - RPE
How can we determine maximum force?
- direct measure of individual/population
- literature
- HandPak: tool that provides maximum voluntary contraction values for sex, hand position, grip type, duration, grip diameter; Software developed to quantify acceptable forces and torques for occupational tasks placing demands on the forearm, wrist and hand.
Identify measurement tools for awkward postures
protractor
goniometry
captiv + imus
- captiv will display duration in awkward postures too.
video playback with manual angle measurement
- requires perpendicular camera angles
Identify measurement tools for repetition
counting
IMUS
post coding on CAPTIV
from video footage
average frequency (times/min): number of movement/cycle time
Identify measurement tools for duration
clock
IMUS
Identify measurement tools for fatigue
MAE-RCRA: maximum acceptable effort - recommended cumulative rest allowance
Fatigue ISO 11228-3/OCRA
Identify measurement tools for psychosocial hazards
Copenhagen psychosocial questionnaire
Psychologically health workplace standard
HSE work-related stress questionnaire
Radius: assess job-based risk of psychological harm
Identify measurement tools for hand-arm vibration
Accelerometers
What is Radius?
Identifies probability of risk factor being in the psychosocial workplace and the severity of risk factor (high vs low)
Facilitates conversations with workers on 18 specific job factors that can cause risk in workplace
What are the guidelines for a pressure sensor?
- Have worker exert the force on the object
* Must have same orientation and grip - Have worker exert the same force on the dynamometer.
- Repeat until measures are close together 3-5 times
What are some factors that affect ability to exert force?
- Internal vs external force
- Lever arm
- Force velocity
- Strength-endurance
- Rest time
- Tolerance of tissue
- Grip type
- Posture
- Grip size
- Gloves
What are some things to consider when choosing a measurement tool
- Accuracy
- Sensitivity
- Data collection
- Interference with task
- Portability
- Cost
- Availability
- are you trained in using it?
How can you determine limit values?
- Epidemiological studies
- Collecting data about human behaviour and trying to make associations within that data
- Cross sectional (going in at one point in time) and longitudinal studies (done over time)
- Prospective (looking forward in time) and retrospective studies (looking back in time)
- OR you can do intervention studies. Which would show which metrics improve when risk is lowered - Lab studies
- Bring people into laboratory situation, take physiological and biomechanical measures with representative subjects
- Meta-analysis of previous research - In vitro studies
- Strain tissue in a petri dish to check when tissue actually fails
Why is it hard to determine limit values?
Validity
–Type of work
–Age of worker
–Environmental conditions
–Organizational factors
–Combination of factors
Reliability
–Trained
–Instrumentation
What are the safe repetition guidelines?
Generally, if cycle time is less than 30 seconds, then may be at risk for injury
What are the force/torque guidelines for pinch and power grips?
1kg in pinch grip
4.5kg for power grip
for durations greater than 4 hours
What are SNOOK tables?
provide MMH design goals, in pounds of weight or force, that are deemed to be acceptable to a defined percentage of the population. This is done by comparing data for each of the specific manual handling tasks against the appropriate table.
What are the 5 steps for assessing for upper limb injury risk?
- observe the job
- task analysis (hierarchical task analysis)
- conduct whole body checklist on tasks (see worksafebc MSI checklists)
- conduct fatigue analysis on timeline (using established guidelines - ISO 112228-3)
- assess the task
List some assessment tools for the hand/wrist
RULA
SNOOK
HAND PAK
arm forcefield
List some assessment tools for the elbow
RULA
3DSSPP
Arm forcefield
List some assessment tools for the shoulder
RULA
3DSSPP
The shoulder tool
UTAH shoulder moment
arm force field
What is QEC
QUICK EXPOSURE CHECKLIST (QEC)
Halfway between checklist and assessment
Go through criteria, creates a score, and level of risk of task
RECOVERY ALLOWANCE ISO 11228-3
Muscle fatigue guidelines
Each 60 minute of consecutive repetitive work should include 10 minutes of recovery
When using guidelines, consider planned and non-planned breaks
Planned breaks
– Graph breaks (must be at least 10 min long to count)
– The last 60 min and 60 min before lunch break do not count
(adequate recovery)
Non-planned breaks
– Alternate tasks which don’t cause repetition to the joint
– Production wait times
- Re-design the task to ensure 10 min of recovery
What is MAE? How did Gibson and Potvin calculate maximum acceptable exertion (MAE) equation ?
maximum acceptable exertion - highest level of exertion (%) a person can safely sustain during repetitive tasks, and it’s often predicted using a formula based on duty cycle (DC), which is the proportion of time spent exerting effort within each cycle
Performed a meta-analysis of studies that looked at the maximum acceptable effort vs frequency in the upper limb
Duty cycle: percentage of time an
individual is engaged in the effort
(effective duration * frequency) / cycle time
- For example, if a worker performs 10 thumb push efforts
within each 65-s cycle and each effort is 0.55 s in duration - then = DC is (10 efforts/cycle × 0.55s/effort)/65 s per cycle,
or DC = 0.085 (8.5% of each cycle)
