13 Ergonomics Automating the retrieval of shopping carts is a good ergonomic solution. Ergonomics is by definition fitting the workplace to the worker. It means more than changing a workstation. It means that the whole environment is designed to fittheworker including directions, controls, printed material, warning signals, mental stress, work schedules, the work climate, fatigue and boredom, material handling, noise, vibration, lighting, mental capacity, the worker=machine interface, and the list could go on. At the present there is no Occupational Safety and Health Administration (OSHA) regulation addressing the hazards caused by poor ergonomic design and problems that result from these issues. Where there are goods and materials involved in the everyday business as in wholesale, retail, and warehousing sectors of the service industry, the potential for ergonomic issues is very real. When the potential for ergonomic-related injuries and illnesses exist, action must be taken to address and prevent these occurrences. This would include management commitment and employee involvement (employee involvement is critical in solving ergonomic-related problems); hazard identification and assessment; hazard control and prevention; and education and training. 13.1 IDENTIFYING HAZARDS Once musculoskeletal disorders’ (MSDs) hazards have been identified, the next step is to eliminate or control them. An effective hazard control process involves identifying and implementing control measures to obtain an adequate balance between worker capabilities and work requirements so that MSDs are not reasonably likely to occur. ß 2008 by Taylor & Francis Group, LLC. During the ident ifi cation and analysis of hazards , you should . Include in the haz ard ident ifi cation and analys is all of the employees in the problem jobs or those who repres ent the range of physical capabi lities of employees in the job. . Ask the empl oyees whether pe rforming the job poses physic al d ifficult ies, and, if so, which physi cal wor k activ ities or condit ions of the job they associate with the diffi culties. An ergonomics haza rd identi ficati on and analysis is a proces s for pinpoin ting the work-rel ated hazards or causes of MSDs. It involves examining the workplace condition s and individua l elem ents or tasks of a job to ident ify and asses s the ergonomic risk factors that are reason ably like ly to be causi ng or contr ibuting to the report ed MSD s. This is an importan t step for those of you whos e ergonom ics programs include early inte rvention when empl oyees report MSDs. Some speci fic wor kers need to be evalua ted since they may not be indicati ve of your average wor ker. This may b e especi ally true of wor kers perfor ming the same task as others. It is imperative that y ou look at sizes of wor kers or handic aps such as the follow ing: . Shorte st employees in the job, because they are likely to have to make the longest reaches or to have a working surfa ce that is too high . Tallest empl oyees because they may have to mai ntain the most excessive awkwar d postu res (e.g., leaning ove r the assembly line, reaching down wi th the arms ) while perfor ming tasks . Emplo yees with the smal lest hands because they may have to exert con- siderably more force to grip and operate hand and power tools . Employees who work in the coldest areas of the workplace because they may have to exert more force to perform repetitive motions . Employees who wear bifoc als because they may be exposed to awkward postures (e.g., bending neck back to see) An asses smen t tool such as is found in Figure 13.1 can b e used to evalua te worke rs in these catego ries. It is also a good idea to conduct a symptom or comfort survey. This allows the worker to tell you where they are experiencing pain or discomfort. They can also tell you what would make it easier to accomplish the work and often suggest very cost- effective solutions. You must remember that there are likely to be situations in which the physical work activities or conditions only pose a risk to the reporting employee. However, other employees who have performed the job for several years do not have (and ne ver have had) difficulties performing the physical work activities of the job. In this case, it might be concluded that the problem is limited to the injured employee . These efforts may include job–task breakdown, videotaping or photographing the job, job or hazard checklists, employee questionnaires, use of measuring tools, or employee symptom or discomfort surveys, are recognized ergonomic evaluation methods. ß 2008 by Taylor & Francis Group, LLC. Ergonomic hazard identification checklist Work Area______________________________ Employees________________________ Date_______________________ Conducted by ____________________________ Reviewed by_______________________ Date_______________________ Answer the following question based on the primary job activities of the worker at this particular task. Use the following responses to describe how frequently the worker is exposed to the job conditions described below: Never—Worker is never exposed to the condition. Sometimes—Workers is exposed to the condition less than three times daily. Usually—Worker is exposed to the condition three times or more daily. Never Sometimes Usually If usually, list jobs to which answer applies here Does worker perform tasks that are externally paced? Is the worker required to exert force with their hands (e.g., gripping, pulling, pinching)? Does the worker stand continuously for periods of more than 30 min? Does the worker sit for periods of more than 30 min without the opportunity to stand or move around freely? Does the worker have to stretch to reach the parts, tools, or work area? Does the worker use electronic input devices (e.g., keyboards, mice, joysticks, track balls) for continuous periods of more than 30 min? FIGURE 13.1 Ergonomic hazard identification checklist. (Courtesy of the Occupational Safety and Health Administration.) (continued ) ß 2008 by Taylor & Francis Group, LLC. Never Sometimes Usually If usually, list jobs to which answer applies here Does the worker kneel (one or both knees)? Does the worker perform activities with hands raised above shoulder height? Does worker perform activities while bending or twisting at the waist? Is the worker exposed to vibration? Is the worker required to worker in unnatural body positions? Does the worker lift or lower objects between the floor and waist height or above the shoulder? Does worker lift, lower, carry large objects that cannot be held close to the body? Does the worker lift, lower, or carry objects weighing more than 50 lb? TERMS Primary job activities—Job activities that make up a significant part of the work or are required for safety or contingency. Activities are not considered to be primary job activities if they make up a small percentage of the job (i.e., takes up less than 10% of the worker’s time) are not essential for safety or contingency, and can be readily accomplished in other ways (e.g., using equipment already available in the facility). Externally paced activities—Work activities for which the worker does not have direct control of the rate of work. Externally paced work activities include activities which (1) the worker must keep up with an assembly line or an independently-operating machine, (2) the worker must respond to a continuous queue (e.g., customers standing in line, phone calls at a switch). FIGURE 13.1 (continued) ß 2008 by Taylor & Francis Group, LLC. While observing the job, employers record a descripti on of each task for use in later risk factor analysis as well as other information that is helpful in completing the analysis: . Tools or equipment used to perform task . Materials used in task . Amount of time spent doing each task . Workstation dimensions and layout . Weight of items handled . Environmental conditions (cold, glare, blowing air) . Vibration and its source . Personal protective equipment worn Hazards cannot be addressed efficiently without an accurate evaluation of the situation. The employee doing the job is one of the best sources of information; they are local process experts. Employees need to be involved in the identification, analysis, and control process because ‘‘no one knows the job better than the person who does it. ’’ Employees have the best understanding of what it takes to perform each task in a job, and thus, what parts of the job are the hardest to perform or pose the biggest difficulties. Workers can best tell what conditions cause them pain, discom- fort, and injuries. They often have easy and practical suggestions on how such problems can be alleviated. Involving workers can make the job process more efficient, and pinpoint the causes of problems more quickly. 13.2 ERGONOMICALLY RISKY ACTIVITIES 13.2.1 W ORK ACTIVITIES Some of the activities that put workers at risk of ergonomically related problems are as follows: . Exerting considerable physical effor t to complete a motion . Doing same motion over and over again . Performing motions constantly without short pauses or breaks in between . Performing tasks that involve long reaches . Working surfaces are too high or too low . Maintaining same position or posture while performing tasks . Sitting for a long time . Using hand and power tools . Vibrating working surfaces, machi nery, or vehicles . Workstation edges or objects pressing hard into muscles or tendons . Using hand as a hammer . Using hands or body as a clamp to hold objects while performing tasks . Wearing gloves that are bulky, too large, or too small ß 2008 by Taylor & Francis Group, LLC. 13.2.2 MANUAL MATERIAL HANDLING Since material handling is common in this sector, specific attention should be paid to the following: . Objects moved are heavy. . Horizontal reach is long (distance of hands from body to grasp object to be handled). . Vertical reach is below knees or above the shoulders (distance of hands above the ground when the object is grasped or released) as in Figure 13.2. . Objects or people are moved significant distance. . Bending or twisting during manual handling. . Object is slippery or has no handles. . Floor surfaces are uneven, slippery, or sloped. Each of these items presents certain potential risk factors. When evaluating any risky activities, the risk factors in the section need to be considered as contributors to potential ergonomic problems. 13.3 ERGONOMIC RISK FACTORS Ergonomic risk factors are the aspects of a job or task that impose a biomechanical stress on the worker. Ergonomic risk factors are the synergistic elements of MSD hazards. The following ergonomic risk factors are most likely to cause or contribute to an MSD: Overhead work FIGURE 13.2 Reaching above the shoulders is an ergonomic hazard. (Courtesy of the Occupational Safety Health Administration.) ß 2008 by Taylor & Francis Group, LLC. . Force . Vibration . Repetition . Contact stre ss . Awkward postu res . Cold tem perat ures . Static postures 13.3.1 DESCRIPTION OF R ISK FACTORS 13.3.1.1 Force Force refers to the amoun t of physi cal effor t that is required to accom plish a task or motion. Tasks or mot ions that requi re appli cation of higher force place higher mechanical loads on musc les, tendon s, ligament s, and join ts. Tasks invol ving high forces may cause musc les to fatigue more quickl y. Hi gh forces also may lead to irritation, infla mmation, stra ins and tears of musc les, tendon s, and other tissues. The force required to complete a movement increases when other risk factors are also involved. For example, more physical effort may be needed to perform tasks when the speed or acceleration of motions increases, when vibration is present, or when the task also requires awkward postures. Force can be internal, such as when tension develops within the muscles, ligaments, and tendons during movement. Force can also be external, as when a force is applied to the body, either voluntarily or involuntarily. Forceful exertion is most often associated with the movement of heavy loads, such as lifting heavy object s on and off a conveyor , deli vering heavy packa ges, pushi ng a heavy c art, or movi ng a pallet. Hand tools that invol ve pinch grips requi re more forceful exertions than those that allow other grips, such as powe r grips . 13.3.1.2 Repetitio n Repetition refers to perfor ming a task or seri es of motions over and over again with little varia tion. When motions are repeated frequently (e.g., every few seconds) for prolonged perio ds (e.g., severa l hours, a work shif t), fatig ue and strain of the muscle and tendons can occur because there may be inadequate time for recovery. Repetition often involves the use of only a few muscles and body parts, which can become extremel y fatigued while the rest of the body is little used. Table 13.1 shows the frequency of repet ition and length of task cycles that are associated with increased risk of injury in repetitive motion jobs. 13.3.1.3 Awkward Postures Awkward postures refer to positions of the body (e.g., limbs, joints, back) that deviate significantly from the neutral position while job tasks are being performed. For example, when a person’s arm is hanging straight down (i.e., perpendicular to the ground) with the elbow close to the body, the shoulder is said to be in a neutral position. However, when employees are performing overhead work (e.g., installing or repairing equipment, grasping objects from a high shelf) their shoulders are far ß 2008 by Taylor & Francis Group, LLC. from the neutral position . Other examp les incl ude wrists bent while typing, bendin g over to grasp or lift an object , twist ing the back and torso while movi ng heavy objects, and squat ting. Awkw ard po stures often are signi fi cant contr ibutors to MSDs because they incre ase the work and the musc le force that is requi red. 13.3.1. 4 Static Postures Static postu res (or ‘‘ static loading ’’ ) refer to physi cal exert ion in which the same posture or position is held througho ut the exertion. The se types of exertions put increased loads or forces on the musc les and tendons, which contribut es to fatigue. This oc curs because not moving impe des the blood flow that is needed to b ring nutrients to the musc les and to carry away the was te product s of muscle metaboli sm. Exampl es of stat ic postu res include gripp ing tool s that cannot be put down , holding the arms out or up to perfor m tasks , or stand ing in one place for prolo nged periods. Antifatigu e mats are helpfu l for cashiers who must stand in one place for long periods of tim e as seen in Figure 13.3. 13.3.1.5 Vibration Vibration is the oscillatory motion of a physical body. Localized vibration, such as vibration of the hand and arm, occurs when a specific part of the body comes into contact with vibrating objects such as powered hand tools (e.g., chain saw, electric drill, chipping hammer) or equipment (e.g., wood planer, punch press, packaging machine). Whole-body vibration occurs when standing or sitting in vibrating envir- onments (e.g., driving a truck over bumpy roads) or when using heavy vibrating equipment that requires whole-body involvement (e.g., jackhammers). 13.3.1.6 Contact Stress Contact stress results from occasional, repeated, or continuous contact between sensitive body tissue and a hard or sharp object. Contact stress commonly affects TABLE 13.1 Repetition and Body Area Body Area Frequency Repetition per Minute Level of Risk Very High Risk if Modified by Either Shoulder More than 2.5 High High external force, speed, high static load, and extreme posture Upper arm=elbow More than 10 High Jack of training, high output demands, and lack of control Forearm=wrist More than 10 High Long duration of repetitive work Finger More than 200 High Source: Courtesy of the Occupational Safety and Health Administration. ß 2008 by Taylor & Francis Group, LLC. the soft tissue on the fingers, palm s, forearms, thighs, shins, and feet. This contact may create pressure over a small area of the body (e.g., wrist, forearm) that can inhibit blood flow, tendon and muscle movement, and nerve function. Examples of contact stress include resting wrists on the sharp edge of a desk or workstation while performing tasks, pressing of tool handles into the palms, especially when they cannot be put down, tasks that require hand hammering, and sitting without adequate space for the knees. 13.3.1.7 Cold Temperatures Cold temperatures refer to exposure to excessive cold while performing work tasks. Cold temperatures can reduce the dexterity and sensitivity of the hand. Cold temper- atures, for example, cause the worker to apply more grip force to hold hand tools and objects. Also, prolonged contact with cold surfaces (e.g., handling cold meat) can impair dexterity and induce numbness. Cold is a problem when it is present with other risk factors and is especially problematic when it is present with vibration exposure. FIGURE 13.3 The use of antifatigue mats for those workers who must stand in static positions for periods of time. ß 2008 by Taylor & Francis Group, LLC. Of these risk factors, force (i.e., forceful exertions), repetition, and awkward postures, especially when occurring at high levels or in combination, are most often associated with the occurrence of MSDs. Exposure to one ergonom ic risk factor may be enough to cause or contribute to a covered MSD. However, most often ergonomic risk factors act in combination to create a hazard. Jobs that have multiple risk factors have a greater likelihood of causing an MSD, depending on the duration, frequency, and=or magnitude of exposure to each. Thus, it is important that ergonomic risk factors be considered in light of their combined effect in causing or contributing to an MSD. Table 13.2 depicts tasks and their risk factors. TABLE 13.2 Tasks and Their Risk factors Physical work activities and conditions: Ergonomic risk factors that may be present (1) Exerting considerable physical effort to complete a motion (i) Force (ii) Awkward postures (iii) Contact stress (2) Doing same motion over and over again (i) Repetition (ii) Force (iii) Awkward postures (iv) Cold temperatures (3) Performing motions constantly without short pauses or breaks in between (i) Repetition (ii) Force (iii) Awkward postures (iv) Static postures (v) Contact stress (vi) Vibration (4) Performing tasks that involve long reaches (i) Awkward postures (ii) Static postures (iii) Force (5) Working surfaces are too high or too low (i) Awkward postures (ii) Static postures (iii) Force (iv) Contact stress (6) Maintaining same position or posture while performing tasks (i) Awkward posture (ii) Static postures (iii) Force (iv) Cold temperatures ß 2008 by Taylor & Francis Group, LLC. [...]... Courtesy of the Occupational Safety and Health Administration 13. 4 PHYSICAL WORK ACTIVITIES AND CONDITIONS The physical work activities and conditions include the following: Physical demands of work Workplace and workstation conditions and layout Characteristics of objects that are handled or used Environmental conditions Table 13. 3 shows the physical work activities and workplace conditions that... Using hand as a hammer (i) Contact stress (ii) Force (12) Using hands or body as a clamp to hold object while performing tasks (i) Force (ii) Static postures (iii) Awkward postures (iv) Contact stress (13) Gloves are bulky, too large or too small (i) Force (ii) Contact stress Manual material handling (lifting=lowering, pushing=pulling, and carrying) (14) Objects or people moved are heavy (i) Force (ii)... physical effort to complete a motion Doing the same motion over and over again Performing motions constantly without short pauses or breaks in-between Maintaining same position or posture while performing tasks Sitting for a long time Using hand as a hammer Using hands or body as a clamp to hold object while performing tasks Objects or people are moved significant distances Layout and condition... your program and procedures, sign and symptom identification, and types of injuries and illnesses Second, train some of the workforce in ergonomic assessment so you will have teams of both management and labor to evaluate ergonomic hazards and make recommendations for controlling the potential risk factors on the jobs in your workplace With proper training you will have an educated workforce who can... rates Reduction in total lost-workdays and lost-workdays per case Reduction in job turnover or absenteeism Reduction in workers’ compensation costs=medical costs Increases in productivity or quality Reduction in reject rates Number of jobs analyzed and controlled Number of problems solved 13. 8 EDUCATION AND TRAINING Education and training can be used in variety of ways The foremost is to train all employees... (distance of hands from body to grasp object to be handled) (i) Force (ii) Repetition (iii) Awkward postures (iv) Static postures (v) Contact stress (continued ) ß 2008 by Taylor & Francis Group, LLC TABLE 13. 2 (continued) Tasks and Their Risk factors (16) Vertical reach is below knees or above the shoulders (distance of hands above the ground when the object is grasped or released) (i) Force (ii) Repetition... people moved are heavy Object is slippery or has no handles Environmental conditions Cold temperatures Temperature extremes and humidity Vibration Noise Illumination Colors Source: Courtesy of the Occupational Safety and Health Administration 13. 5 LIMITS OF EXPOSURE To determine the real risk, you need to look at the duration, frequency, and magnitude (i.e., modifying factors) of the employee’s... hazard, and last, identify and evaluate MSD hazards when you change, design, or purchase equipment or processes in problem jobs 13. 6.1 IDENTIFY CONTROLS There are many different methods you can use and places you can go to identify controls Many employers rely on their internal resources to identify possible controls These in-house experts may include the following: Employees who perform the job and. ..TABLE 13. 2 (continued) Tasks and Their Risk factors (7) Sitting for a long time (i) Awkward posture (ii) Static postures (iii) Contact stress (8) Using hand and power tools (i) Force (ii) Awkward postures (iii) Static postures (iv) Contact stress (v) Vibration (vi) Cold temperatures (9) Vibrating working surfaces, machinery, or vehicles (i) Vibration (ii) Force (iii) Cold temperatures... with the above-mentioned physical aspects Employers should examine a job in which an MSD has occurred to identify the physical work activities and workplace conditions and then evaluate the risk factors to make an assessment of the work environment ß 2008 by Taylor & Francis Group, LLC TABLE 13. 3 Physical Work Activities and Conditions Physical aspects of jobs and workstations Physical demands of work . perfor m tasks , or stand ing in one place for prolo nged periods. Antifatigu e mats are helpfu l for cashiers who must stand in one place for long periods of tim e as seen in Figure 13. 3. 13. 3.1.5. performing work tasks. Cold temperatures can reduce the dexterity and sensitivity of the hand. Cold temper- atures, for example, cause the worker to apply more grip force to hold hand tools and objects down wi th the arms ) while perfor ming tasks . Emplo yees with the smal lest hands because they may have to exert con- siderably more force to grip and operate hand and power tools . Employees