V.C - I - Back & Ergonomics (Tracey) - NIOSH Lifting Equation, Epidemiology, Erector spinae, Loads on spine, Facet Joint Movements

Question 1

What is the study of peoples efficiency in their workplace known as?

Answer 1

This is known as ergonomics

Question 2

In this set of cards, we will be looking at how anatomy affects the work place Specifically going to look at the musculoskeletal disorders in the work place We will be looked at WRMSDs What does this acronym stand for?

Answer 2

WRMSDs - Work Related MusculoSkeletal Disorders

Question 3

Lots of research is being done into what can cause and prevent back pain but it has had little or no effect on decreasing the incidence of back pain The national institute for occupational safety and health (NIOSH) found in 1981 that 60% of lower back pain was due to overexertion NIOSH devised a lifitng equation to calculate the recommended lifting weight limit for a person What was this equation?

Answer 3

RWL = LC x HM x VM x DM x AM x FM x CM

• * LC - load constant
• * M - constant multiplier for each measurement
• * H - horizontal distance of hands
• * V - vertical distance of hand
• * D - vertical travel distance
• * A - angle of asymmetry
• * F - frequency of lifting
• * C - coupling classification On the next card we will state what each of these means

Question 4

• * LC - load constant
• * M - constant multiplier for each measurement
• * H - horizontal distance of hands
• * V - vertical distance of hand
• * D - vertical travel distance
• * A - angle of asymmetry
• * F - frequency of lifting
• * C - coupling classification On the next card we will state what each of these means

What do each of these measurements mean? This questions isn’t relevant to the LC and M constants

Answer 4

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Question 5

State what each measurement means again * H - horizontal distance of hands * V - vertical distance of hand * D - vertical travel distance * A - angle of asymmetry * F - frequency of lifting * C - coupling classification

Answer 5

H - horizontal distance of hands away from the midpoint between ankles V - vertical distance of hands from the ground D - vertical travel distance - difference between the original and end vertical distances A - angle of asymmetry - anglular measure between how far the object is displace from mid-saggital plane of workers body at beginning and end of lift F - frequency of lifting - number of lifts/minute in 15 minutes C - coupling classification - GOOD, FAIR or POOR - quality of handle to object coupling

Question 6

What does NIOSH stand for again and what did they find the maximum recommended weight limit for any person to carry?

Answer 6

The maximum RWL is 23 kg

Question 7

Health and Safety Executive (HSE) statistics (Great Britain) What trend did HSE find in MSDs since 2001/02?

Answer 7

Since 2001/02 there has been a downward trend of MSDs but in recent years, this trend has flattened out

Question 8

What is the main work reason mentioned to GPs for, or exacerbating, MSD?

Answer 8

Heavy lifting Keyboard work Manipulating materials

Question 9

What are the commonest occupations for MSD to arise?

Answer 9

Specialised construction Agriculture (farm workers) Human health and residential care (healthcare workers)

Question 10

What are the most common sites for MSDs to occur during work?

Answer 10

Most common - lumbar spine - weight bearing aspect of vertebral column and therefore at risk when heavy lifting 2nd most common - hand/wrist/arm - due to keyboard work

Question 11

The active stabilising mechanisms for the back include muscles, ligaments and the facet joints What muscle is the main limiter of flexion of the vertebral column?

Answer 11

The erector spinae muscles group due to eccentric muscle contraction Iliocostalis, longissimus, spinalis

Question 12

What type of skeletal muscles fibres are the erecotr muscle group predominantly said to be?

Answer 12

The erector spinae muscle group are predominantly Type 1 fibres - slow twitch Usually type 1 generate small forces but erector spinae must generate large forces due to short moment arm

Question 13

There are a lot of small intrinsic muscles helping to maintain back posture as well. What are these?

Answer 13

The transversospinales muscle group Multifidus Semispinalis Rotatores Levator costarum Intertrasversarii Interspinales

Question 14

Strong ligaments is an important mechanism for resisting load What is the benefits of having a curved spine to resist load?

Answer 14

This means that the spine can increase the lordosis or kyphosis in a response to load whereas a vertical spine would either be resist load or fracture

Question 15

What is the motion segment made up of? What happens to the parts of the IV disc during extension of the spine?

Answer 15

The motion segment is made up of half the vertebral body above, half the vertebral body below and the IV disc - this is the anatomical segment allowing for motion During extension of the spine, the vertebral bodies compress the posteior annulus fibrosus whilst the nucleus pulposus wlll move towards the anterior aspect of the disc This acts a self-limiting stretch mechanism as the nucleus pulposus movement makes the anterior annulus fibrosus more taught limiting further extension

Question 16

Vertebral column constantly subjected to stresses due to loads such as what? (try name four)

Answer 16

Body weight Tension in ligaments Compression due to extensor muscles Any external load Just the weight of the head in cervical region which is why the discs are thinner whereas fatter discs in thoracic/lumbar region

Question 17

Why is there constant compression of the vertebral bodies due to the extensor muscles? (erector spinae)

Answer 17

This is because the centre of gravity of the vertebral column is slightly anterior to the vertebrae therefore the erector spinae are constantly slightly tensed

Question 18

Under normal circumstances, what is the greatest compressive force of the IV disc and why?

Answer 18

Under normal circumstances the greatest compressive force of the IV disc is the erector spinae muscles This is because there moment arm is very short and therefore the forces required are great Short moment arm of the muscles of the back and therefore the forces required by the erector spinae to maintain extension if person bends over are very large

Question 19

What position is the load on the vertebra dramatically reduced?

Answer 19

When the person is lying supine

Question 20

Study found that there was almost 500 times the compressive force on the disc when peson flexes to lift something up compared to when standing upright When can the compressive forces on the disc actually be lowered if the person is supine?

Answer 20

Lifting the knees when the person is lying supine will allow the psoas major muscle to relax meaning they are not pulling on the lumbar spine hence the reduction in compressive forces

Question 21

Approximately what percentage of the population will suffer back pain at some stage?

Answer 21

60-80%

Question 22

Lets discuss the movements at the facet joints of the back and neck at different regions of the vertebral column State the angle of movement at the cervical region

Answer 22

Cervical region - * flexion - 25 degrees * extension - 85 degrees * lateral flexion - 40 degrees * rotation - 50 degrees

Question 23

Lets discuss the movements at the facet joints of the back and neck at different regions of the vertebral column State the angle of movement at the thoracic region

Answer 23

Thoracic region * flexion and extension - combined movements between 50-70 degrees * lateral flexion - 20-25 degrees * rotation - 30 degrees

Question 24

Lets discuss the movements at the facet joints of the back and neck at different regions of the vertebral column State the angle of movement at the lumbar region

Answer 24

Lumbar region flexion - 55 degrees extension - 30 degrees lateral flexion - 20-30 degrees in adults (60 degrees in children) rotation - almost 0