1. © SafetyNet Centre for Occupational Health & Safety Research Memorial University, 2012 Basic Ergonomics E RGO -T EAM A PPROACH TO P ARTICIPATORY E RGONOMICS Developed by: Scott N. MacKinnon, PhD Edited by: David M. Antle, MSc, PhD (candidate)

2. Ergonomics is the scientific discipline concerned with the fundamental understanding of interactions among humans and other elements of a system, and the profession that applies theory, principles, data, and methods to design in order to optimize human well-being and overall system performance. International Ergonomics Association 2 What is ergonomics?

3. Ergonomists contribute to the design and evaluation of tasks, jobs, products, environments, and systems in order to make them compatible with the needs, abilities, and limitations of people. International Ergonomics Association TaskOperator 3 What do Ergonomists do?

4. “Fitting the job to the worker” 4

5. Benefits of Ergonomics Ergonomics helps to prevent injuries Ergonomics has other benefits - Improves quality of work - Improves quality of life - Reduces fatigue and discomfort 5

6. Participatory Ergonomics (PE) PE is a general technique of empowering employees to control the design of their workplaces and plan their work activities. The premise is that workers are most familiar with their own work situation. The success of any OHS program relies, in part, on harvesting and nurturing the tacit knowledge of the key stakeholders. 6

7. PEOPLE ORGANIZATIONAL DESIGN TECHNOLOGY (From Hendrick, 1986) Environment 7

8. Ergonomics Awareness Training Recognize workplace risk factors for musculoskeletal disorders and understand general methods for controlling them. Identify the signs and symptoms of work-related musculoskeletal disorders that may result from exposure to such risk factors, and be familiar with the company’s health care procedures. Know the process the employer is using to address and control risk factors, the employee’s role in the process, and ways employees can actively participate. Know the procedures for reporting risk factors and musculoskeletal disorders, including the names of designated persons who should receive the reports. 8

9. Risk Recognition Regular workplace inspections Consultation with employees Task analysis Direct observation Accident/incident investigation Analysis of workplace injury records 9

10. Work-Related Musculoskeletal Disorders (WMSDs) Collective term for painful disorders brought on by acute or cumulative exposure to work activities. WMSDs can affect: - Muscles - Tendons - Nerves - Skeletal Tissue 10

11. WMSD are also known as: Repetitive motion injuries - RMI Repetitive strain injuries - RSI Cumulative trauma disorders - CTD Occupational cervicobrachial disorders - OCBD Overuse syndrome Regional musculoskeletal disorders - RMD Soft tissue disorders Upper extremity cumulative trauma disorders - UECTD Work related upper limb disorder - WRULD 11

12. Factors to consider when evaluating WMSDs: the area of the workplace where injury or pain is reported the occupation and job demands of the injured person length of shift worked (eg. night or day) the part of the body injured - examples include: back, neck or shoulder the nature of the injury - examples include: strain, sprain, or inflammation the type of accident - examples include: overexertion and physical stress in lifting the causes/mechanisms of the injury (eg. repetitive movement, heavy loads) 12

13. What causes WMSDs? heavy, frequent, or awkward lifting pushing, pulling or carrying loads working in awkward postures hand intensive work 13

14. How do WMSDs occur? WMSDs do not happen as a result of a single accident or injury. They develop gradually as a result of repeated trauma. Excessive stretching of muscles and tendons can cause injuries that only last a short time. But repeated episodes of stretching causing tissue inflammation can lead to long- lasting injury or WMSDs. 14

15. Muscle Injury A muscle contraction that lasts a long time reduces the blood flow. Consequently, the substances produced by the muscles are not removed fast enough and accumulate. The accumulation of these substances irritates muscles and causes pain. The severity of the pain depends on the duration of the muscle contractions and the amount of time between activities for the muscles to get rid of those irritating substances. 15

16. Tendon Injury Tendons consist of numerous bundles of fibers that attach muscles to bones. Tendon disorders are related to repetitive or frequent work activities and awkward postures. 16 Images courtesy Canadian Centre for Occupational Health & Safety http://www.ccohs.ca/oshanswers/diseases/tendon_disorders.html

17. Nerve Injury Nerves carry signals from the brain to control activities of muscles. They also carry information about temperature, pain, and touch from the body to the brain, and control bodily functions such as sweating and salivation. With repetitive motions and awkward postures, the tissues surrounding nerves become swollen and squeeze or compress nerves. Compression of a nerve causes muscle weakness, sensations of "pins and needles" and numbness. Dryness of skin and poor circulation to the extremities may also occur. 17 Image courtesy Canadian Centre for Occupational Health & Safety http://www.ccohs.ca/oshanswers/diseases/carpal.html

18. What are the signs and symptoms of work-related injuries? joint stiffness muscle tightness muscle “burning” pain through ends of range of motion redness and swelling of the affected area sensations of "pins and needles“ numbness skin colour changes decreased sweating of the hands localized “shooting” pain during effort 18

19. 3 Stages of Pain Stage 1 - gradual onset - aching and tiredness of the affected limb occur during the work shift - disappears with rest (overnight, weekend) - no reduction of work performance Stage 2 - aching and tiredness occur early in the work shift and persist at night - reduced capacity for repetitive work - rest does not make pain subside Stage 3 - aching, fatigue, and weakness persist at rest - inability to sleep and to perform light duties - medical treatment required 19

20. How can we prevent WMSDs? Job Design - mechanization - job rotation - work to rest ratios - job enlargement and enrichment - team work Workplace Design and Layout Tools and Equipment Design Worker selection - training - conditioning - posture 20

21. What are the workplace risk factors for WMSDs? What are the task risk factors? 21

22. Risk Factors Risk of injury depends upon: duration of exposure frequency of exposure intensity of exposure combinations of risk factors 22

23. A constrained posture involving various body segments and joints can increase the risk of injury, even if the loads you are working with are very light. Constrained postures: - reduce the ability for muscles to produce force - reduce the volume inside a joint and cause tissues to rub against each other, or bony structures, leading to injury - reduce blood flow increasing fatigue and discomfort and can damage nerves and tissue (eg. Carpel tunnel syndrome) Risk Factors Constrained postures 23

24. Risk Factors Repetition Workers performing highly repetitive tasks are at the highest risk for WMSDs. Tasks requiring repetitive movements always involve other risk factors for WMSDs such as fixed body position and force. A job task might require spending only a very small amount of time in a non-neutral posture but the worker may have to complete that same task several times in the course of a shift with this repetition potentially adding to the risk associated with the task. In addition, repetitive movements of light objects can result in injury caused by the cumulative load on the muscles, joints, and tendons over the course of a shift or a work week. 24

25. Risk Factors Force The force required to do the task also plays an important role in the onset of WMSDs. More force equals more muscular effort and consequently, more time is needed to recover between tasks. Since in repetitive work, as a rule, there is not sufficient time for recovery, the more forceful movements lead to fatigue much faster. The amount of force needed to produce fatigue depends on: - the weight of the tools and objects - tool placement in relation to the worker's body. - the shape of the tool - condition of repair of the tool. 25

26. Press Pinch (palm) Pulp Pinch Lateral PinchFinger Press Grasp 26 Images courtesy Canadian Centre for Occupational Health & Safety http://www.ccohs.ca/oshanswers/diseases/rmirsi.html

27. Risk Factors Pace of Work Pace of work determines the amount of time available for rest and recovery of the body between cycles of a particular task. The faster the pace, the less time is available and the higher the risk for WMSDs. When the worker has no control over timing and speed of work because of external factors like assembly line speed or quota and bonus systems, stress levels increase – as do errors. With higher stress level comes muscle tension causing fatigue and increased risk for WMSDs. 27

28. Risk Factors Temperature and Environment Temperature and humidity affect the worker performing repetitive work. When it is too hot and too humid, the workers tire more quickly and become more susceptible to injury. Cold temperatures decrease the flexibility of muscles and joints increasing the likelihood of injury. Noise creates cognitive stress and can negatively impact on work tasks and perceptions of fatigue and discomfort. 28

29. Risk Factors Vibration Vibration affects tendons, muscles, joints, and nerves. Workers using vibrating tools may experience numbness of the fingers, loss of touch and grip, and pain. 29

30. Risk Factors Personal Factors age sex previous trauma job experience morphological - strength - aerobic fitness - anthropometry (body shape) nutrition vitamin and mineral deficiency disease processes - rheumatoid arthritis - diabetes mellitus - renal dialysis - thyroid abnormalities hormonal factors - diurinal variations - menstruation - oral contraceptives - pregnancy 30

31. Risk Factors Measuring Cumulative Loading Injuries do not usually occur from exposure to 1 event Cumulative exposure to risk factors over days, weeks, months or years add up to produce WMSDs 31

32. Cumulative Loading Some examples of jobs where cumulative loading can lead to injury are: 1) Typing on a keyboard, where the force required to strike the key is very low but can still lead to injury from long hours of continuous typing, particularly if the upper limb, wrist, and hands are held in an awkward posture increasing strain on tissues. 2) Packing a shelf or pallet with 5 lb (2.2 kg) boxes where the load may be light but repeated lifting many times throughout a day can lead to fatigue, pain, and potential injury. 32

33. The Effect of Fatigue on Injury Tolerance Soft Tissue Tolerance TIME SPINAL LOAD Soft Tissue Tolerance: Fatiguing Effects Vertebrae Compressive Strength: ↓ by ~ 30% with 10 loading cycles ↓ by ~ 50% with 5000 loading cycles 33 Brinckmann P, Biggemann M, Hilweg D. (1988). Fatigue fracture of human lumbar vertebrae. Clinical Biomechanics, 3 (Suppl. 1), s2-s23.

34. Manual Materials Handling (MMH) activities - lift, lower, carry, push, and pull characteristics - static or dynamic - coordinated efforts from multiple joints and body areas 34

35. MMH Considerations for WMSDs The amount of effort associated with completing a particular task, such as lifting and carrying an object, determines, to a significant degree, the strain that will be placed on joints, muscles, and tendons. Effort is determined not only by the weight of the object being lifted or moved by the force required to push or pull, but also by: - the distribution of that weight between joints, muscles, and tendons - the distance between the object and the joint in question - the distance or height an object must be lifted to, moved, carried, pushed, pulled, etc - the amount of bending or twisting of joints during actions (particularly for the back) 35

36. MMH Considerations Always try to get your body in a desirable lifting posture. In most jobs the work space will influence how the load is manipulated. A desirable posture has the back kept upright and the knees bent. In this posture most of the vertical displacement of the load will be done with the strong leg musculature. Load characteristics, such as size and shape, prevent us from adopting this posture – so we have to learn how to minimize the negative effects a less than desirable posture will have on our bodies. 36

37. Minimizing the Effects of the Load on Your Body Keep the load close to your body!! This significantly reduces the ability of a load to bend your back and stress your arms. The closer you keep the load to your body the less effort, strength, and energy you have to spend in performing the task. The amount of muscular effort and the risk of injury increase as the location of the load moves away from the joint centre, or centre of the body. To illustrate, try holding a book by your side for 3 minutes. Now try holding the same object for the same period of time at arm’s length straight out from your body. MMH Considerations 37

38. MMH Considerations Volume of the load Just because a load is light doesn’t mean it can’t add unbearable stresses to your back and shoulders. A large volume means that the load can’t be held near your body. Some loads do not have their mass evenly distributed making it difficult to hold and control the load. 38

39. How wobbly or unstable is the load? If the mass is not solid, such as a pail of water, then the load can shift while you are transporting it. This rocking motion makes the load much more difficult to handle. MMH Considerations 39

40. A sideways bend or twist in your lower back reduces its ability to produce force and increases the risk of overexertion of the soft tissues of the trunk. MMH Considerations 40

41. Keep your body square to your work or load If your feet, hips, and the load you are manipulating are all facing the same direction, you have a more neutral spine posture without excessive bending or twisting. If you want to turn the load, it’s best to shuffle and pivot your feet to maintain neutral back/spine postures. MMH Considerations 41

42. Avoid low and high lifts, pushes, pulls Keeping the direction of the exerted force near the middle of your body is important. As the load or the force moves away from the middle of your trunk you become less stable and prone to slips and trips. High or low exertions are not mechanically efficient. Muscles are not in an optimal position to produce force and one often has to use the smaller, weaker muscles and awkward joint positions to complete the task. MMH Considerations 42

43. Avoid moving when vision is obstructed If you can’t see obstacles, even ones expected to be within your workplace, then trips and collisions will occur. Vision provides important information to the brain about postures and how to implement safe movement strategies. MMH Considerations 43

44. Use handles or a secure, symmetrical grip whenever possible Handles will ensure you apply force evenly to the load you are handling. Handles require less muscular effort for both the arm and back muscles, so you will feel less fatigue at the end of a shift or rotation. MMH Considerations 44

45. Be careful in confined and restricted spaces! Activities in confined or restricted spaces often result in injury. Confined or restricted spaces will force you to alter your mechanics or adopt awkward postures. Anytime you have to reach to exert a force you will likely be bending or twisting your spine. NEVER intentionally bend or twist your spine when performing a manual materials handling activity. MMH Considerations 45

46. Psychological (psychosocial) Factors Psychological factors also contribute to fatigue and risk of injury at work. Issues such as working hours, job demands, job control, social support, and job security all impact on perceived workload, which in turn impacts on the employees’ health. Perceived workload can impact on the attention employees pay to bodily sensations and pain sensitivity. Psychological stressors can influence work behaviours and impact biomechanical loads through changes in posture, movements, and exerted forces. Gathering information on psychosocial factors requires careful interview techniques with employees to get their perspectives and explanations. 46

47. Review of WMSDs Hazard Identification with Ergo-Team What are the key physical factors that impact on WMSD risk associated with the selected tasks? For example: - different weights? - distance the load must be moved? - the frequency of lifting? - the position of the trunk, neck, shoulder, forearm, wrist, and hands? - positions that are further from neutral posture? 47

48. Review of WMSDs Hazard Identification with Ergo-Team (cont’) What are the key psychosocial factors that impact on WMSD risk? For example: - control over the work pace? - opportunities to adapt the work and for workers to use their own strategies to make work easier or reduce fatigue/discomfort? - whether workers feel like they have input into work design and organization? - whether they share work tasks between them in a particular way? 48

49. What are some changes to the work organization that could improve the work tasks? For example: - Are the heights of the load origin and destination adjustable? - Can you add some mechanical aids? Conveyer belts, etc. - Can you change the spatial layout of the line? - Can the employees switch tasks throughout the day so that each can do an ‘easier’ job some of the time? - Are there potential problems that could come from changing the organization of the equipment or job (production slow- downs or increases upstream/downstream)? Review of WMSDs Hazard Identification with Ergo-Team (cont’) 49

50. Kroemer, K.H.E., Kroemer, H.B., Kroemer-Elbert, K.E. (2001). Ergonomics: How to Design for Ease and Efficiency (2 nd Ed.). New Jersey: Prentice Hall. Konz, S., Johnson, S. (2000). Work Design: Industrial Ergonomics (5 th Ed.). Arizona: Holcomb Hathaway. Wilson, J.R. & Corlett, E.N. (Eds.) (1998). Evaluation of Human Work: A Practical Ergonomics Methodology (2 nd Ed.). Philadelphia, PA: Taylor & Francis. Ergonomic Resources 50