Manual Material Handling
How many spinal discs between each vertebrae?
1
How many people are currently experiencing low back pain?
1 in 7
Three worker capacities that require consideration when evaluating manual material handling tasks
1. Biomechanical capacity 2. Physiological capacity 3. Psychophysical capacity
Guidelines for risk reduction
1. Limit weight of load 2. Limit horizontal distance of lift 3. Limit vertical distance of lift 4. Optimize vertical location of hands 5. Limit asymmetric lifting 6. Optimize coupling 7. Maximize object stability 8. Maximize use of lifting aids
Women can support _______ less spinal compression force due to the smaller size of their vertebrae
17%
The compression tolerance of a spinal disk is between _____________
2-12kN
spinal anatomy - how many vertebrae?
24
In the UK, __________ of all reported accidents involved manual material handling and were associated with ____________ million workdays
27%, 12.3
Aerobic capacity is _________ lower at age 65 than at age 25
30%
Women have ______ lower aerobic capacities than men
30%
Wearing a single pair of gloves can reduce grip strength up to ____
40%
According to US department of labor, ________ of all back injuries due to lifting occurred in manufacturing settings
42%
Economic consequences range between _____________ dollars per year
45-54 billion
Lack of proper handles or handhold cutouts reduces strength by _____________
5-10%
Of all injuries attributed to overexertion, ______ occur during lifting
52%
What percentage of overexertion injuries during lifting are to the back?
56%
Breakdown of incidents causing back pain (2)
56% occurred while bending; 33% while twisting/turning; 27% while standing
Wearing two pairs of gloves at once can reduce your grip strength up to ______
60%
MSDs account for nearly ______ of doctor's visits per year in the U.S.
70 million
A person has a _______ chance of developing low back pain during their lifetime
70%
A survey of _____________ showed that lifting equipment was not available in _______________ of the cases
708 injury cases; 60%
Overexertion injuries account for _______ of musculoskeletal injuries occurring in the workplace
76%
Breakdown of incidents causing back pain
77% occurred while lifting; 16% while placing; 15% while carrying
Physiological capacity
As aerobic capacity increases, more oxygen can be sent to cells to create energy for muscles
Degenerative joint disease
As spinal discs compress, vertebrae come in contact, causing painful bone damage and the eventual fusion of vertebrae; Occurs over time; associated with aging.
Recommended handle dimensions
Be 4.5" or longer and 0.75"-1.5" wide Have at least 2" of clearance between the handle and the object Be of cylindrical shape to fit the hand Made of a non-slip material
lifting "power zone"
Below the shoulders and above the knees and close to the body
Recommendations to reduce weight of a load
Consider packaging material in smaller containers where possible Establish team lift policies in situations where loading exceeds recommended limits Use lifting aids where possible
Examples of transportation devices
Conveyors, Carts, Turntables, Hand trucks, Forklifts
Examples of lifting devices
Cranes, Lift/tilt/scissor tables, Vacuum lifting device, Self leveling tables, Tool balancers
Back belt Cons
Do not relieve stress to the spine or back muscles Do not reduce the severity of work-related injuries May give workers a false sense of strength
NIOSH advantages
Easy to apply Low cost Requires no special equipment Allows for quick comparison between tasks Can be used to guide and formulate ergonomics initiatives
NIOSH limitations
Evaluates two-handed lifting and lowering only Assumes worker is not in restricted workspace Does not apply to seated or kneeling workers
annulus fibrosus
Fibrous outer layer if the disc
Lifting a load with a high weight can cause
High compression in the discs of the back Higher strength requirements Higher energy expenditures Higher stresses on tissues and joints
Asymmetrical lifting results in:
High spinal disc compression, Reduced strength, Increased cardiovascular demands
Job Enlargement
Increasing the variety by combining jobs or adding tasks to a job
Recommendations for weight lifting
Modify lift so that it can occur within their power zone Perform heavy work tasks without bending, stooping, or reaching
Spinal stenosis
Narrowing of the spinal canal - most often in the lower back. Involves irritation or injury of the spinal cord or nerves.
NIOSH lifting equation origin
Originally developed by Waters at al. in 1981; revised in 1993
Herniated disk risk factors
Overuse, Exercise, Heavy lifting
Risk factors for back strains
Overuse, Overextension, Exercise, Heavy lifting
Examples of administrative controls
Providing safe lifting training Job rotation Job enlargement Adjustment of work schedules, work pace, or work practices Providing adequate recovery time
The NIOSH lifting equation assigns a ______________________ to a specific task
Recommended Weight Limit
Risk factors for back sprains
Repetition, Overextension, Sudden movements
Job Rotation
Rotating employees through different jobs
Which of these lifting techniques is safe?
Squat lift, not stoop lift
Types of back injury
Strain, Sprain, Spinal stenosis (Disc herniation/Degenerative joint disease)
spinal stenosis symptoms
Tingling, numbness, and weakness to severe pain and paralysis. Cramping and numbness in legs, back, neck, and arms
Asymmetric lifting occurs when there is:
Twisting, Lateral bending, Asymmetric placement of hands, Asymmetric center of mass, Lifting with one hand
Object stability recommendations
Use manual material handling tools (i.e. pallet trucks, hand trucks, etc.) to move awkward or dangerous objects Contain objects in rigid containers for lifting where possible
Lifting Index and ranges
Used to determine recommended action >3: Unacceptably Hazardous - Engineering Changes Required 1-3: Requires Task or Administrative Changes 0-1: Acceptable
Cracks in the spinal disc occur...
With age and with exposure to manual material handling
Sprains in the back occur when...
a ligament is overstretched or torn
Strains in the back occur when...
a muscle or the tendon that connects it to a bone is overstretched or torn.
Factors that influence aerobic capacity
age, gender, fitness, nature of work
frequency of lift
an important risk factor related to the prevalence of low back pain
nerve impingement can occur in the spinal disc when...
as pressure increases, fluid from the nucleus pulposus seeps through the outer layer
Biomechanical capacity
calculated by measuring the forces and movements on body joints and soft tissues, concerns compressive and sheer force
Label each of the curves in the spine (ignore last one, it's sacral)
cervical, thoracic, lumbar
Engineering controls
changes to job design, workstation layout, and tool use to reduce employee exposure to ergonomic risk factors
______________________ on the spinal discs caused by ____________________ can cause back injury
compressive forces; poor lifting position
Contents can shift during a lift, which as a result...
drastically changes loads to the body
Lifting loads near floor level can result in ________________________ in the lower back.
high compressive forces
Sagging objects or unstable contents present...
higher risk of injury
Which image is better and why?
image (B) because the reduced moment arms result in 18% less disc compression force
A combination of heavy loads with frequent ___________________________ will result in physical fatigue and greater risk of injury
lifting, walking, and carrying
What are the names of the 3 natural curves in the spine?
lumbar, thoracic, cervical
Administrative controls
management-dictated work practices and policies to reduce or prevent exposures to ergonomic risk factors
NIOSH assumptions
maximum compressive force: 3.4kN Working height: 75cm Physiological criteria: 9.5 kcal/min Psychosocial criteria: lifts should be acceptable for 75% of female workers and 99% of male workers
(In a survey) Lifting equipment was available but not used in __________ of the cases because the equipment was:
more than 30% Not practical to use Not deemed necessary Not working Too time consuming to use
A team can handle ____________ than one person could alone, but __________ than the sum of an individual's capacity
more weight, less weight
A worker's strength is influenced by their
motivation and willingness
Overexertion injuries are linked to
physical and psychological stress
Aerobic capacity increases with...
physical fitness
Calculations for the NIOSH equation are performed twice, once for the ________________________ and once for the _______________________
point of origin; point of destination
Scissor lifts ________________________________________________ , eliminating the need to reach for the object
raise and lower the height of the work surface
Lifting above the shoulder results in __________________ and _____________________ in the lower back
reduced strength; concentrates compressive forces
Things that reduce grip:
slippery surfaces and pinch grip
Use _________ to lift smaller loads.
squat lift
As the horizontal distance between the load and the hands increases, ___________________________________ and __________________________________________.
strength decreases; spinal disc compression increases
Ligament
strong bands of inelastic fibrous tissue that connect bone to bone
L4/L5
the area where most lower back injuries occur (bottom disc)
Overexertion injuries occur when...
the load of a job exceeds the capacity of the worker
Herniated disk occurs when...
the outer ring of an intervertebral disc is torn, allowing the soft central portion to leak or bulge out.
Recommendations for asymmetrical lifting
turntable inserts allow the worker to easily reach the items without having to rotate or twist the body
NIOSH lifting equation
used to determine maximum recommended weight of lift based on calculations of compressive forces in the L5/S5 discs of human cadavers
the spinal disc is strongest in __________________ and weakens with age
young adults
