Midterm practice quesions from each group

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Apr 3, 2024

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Group 20 Which of the following statements are TRUE? 1. In the Revised NIOSH Lift Equation, the larger the recommended weight limit (RWL) or the lower the lifting index (LI), the more protective the task is to workers. [TRUE] 2. Observing one cycle and/or 5 minutes of a task is adequate when measuring repetition or exposure of a task [FALSE] 3. When making a design to accommodate the 5th percentile female through the 95th percentile male, you are accommodating for 95% of the population [FALSE] 4. When calculating the Bloswick Shoulder Movement, the load should be divided in half if it is a 2-handed lift. [TRUE] 5. The human factors engineering approach to design is a cycle of creating, evaluating, and understanding. [TRUE] Group 21 Given below is a photo of a bricklayer in the middle of a task of building a wall. Inspect the image and answer the following questions: a) Perform a REBA analysis based on the joint angles/posture visible in the image. If any assumptions are made (even with respect to prior knowledge), please list them. Show all numbers and calculations used to get to your final REBA score. i) Assume that the load of each brick is 5 lb. ii) Assume Wrist Score = +1 and Coupling = +2. iii) Assume Activity Score = +2. b) List 2 musculoskeletal disorders which might occur from repeated occurrences of the task as it is. c) Based on the REBA analysis, which 2 muscle groups would you target the most in improvements? Give 1 reason for each.

Source Correct Answer: a) REBA analysis Neck: 2 Legs: 2 Trunk: 4 Posture Score A = 6 Force/Load Score = 0 Score A = 6 Upper Arm: 3 Lower Arm: 1 Wrist: 1 Posture Score B = 3 Coupling Score = 2 Score B = 5 Table C = 8 Activity Score = 2 Final REBA Score = 10, high risk, investigate and implement change

b) i) Chronic back pain could occur in the form of slipped discs and sciatica due to sustained back flexion accompanied by a relative lack of knee extension in the frontal plane. ii) Myofascial pain syndrome could occur due to a high degree of sustained neck extension with respect to the torso in the frontal plane. iii) Rotator cuff tendonitis, from working with arms elevated more than 60 degrees from the trunk (p. 438 in “Musculoskeletal Disorders” book in module 2) for long periods of time. iv) Bicep tendonitis can be caused due to repeated arm extension with a load in the frontal plane. c) Based on the REBA analysis, the 2 muscle groups which would need the highest priority are: ● Back: Due to the highest endpoint given as per the REBA analysis along with a very steep angle of flexion accompanied with an inappropriate hip hinge movement. ● Neck: Due to repeated neck extension occurring in every cycle of the task as well as a maximum REBA score given. Group 1 Q: Here is an Amazon worker who needs to carry different loads of different weights every day. As a matter of fact, after years and years of work, his back hurts consistently and he wants to know on average how much pressure his back feels each time he moves a

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load. Here is a graph of how he works daily and please find out how much back compressive force he experiences every time. Solution: Back Posture (A) = 3 * 160 * sin(30) = 240lb ; Load Moment(B) = 0.5 * 10 * 20 = 100lb ; Direct Compresion(C) = 0.8*(80+ 10) = 72lb; Hence the total back compressive force is A + B + C = 412lb. Q: Given that a person has a body weight of 150 pounds, they're lifting a load of 40 pounds at 67 degree angle, and the horizontal distance is 12" calculate the estimated back compressive force. A: 405 + 240 + 92 = 737 Q: A man weighing 160 lbs is picking up a box from the ground. The box weighs 20 lbs, and the man's back angle is 90 degrees from the vertical. He lifts the box with a horizontal distance of 20 inches. Calculate the total back compressive force. Based off the force, should changes be made to the action? A: BW = 160 lbs, LW = 20 lbs, HB = 20 inches Back = 3 * 160 * 1 = 480 Load = 0.5 * 20 * 20 = 200 Direct = 0.8[(160/2) + 20] = 80 Total Force = 480 + 200 + 80 = 760 lbs Yes, changes should be made to this action because the total estimated compressive force is 760 lbs, which exceeds the comparison value of 700 lbs. However, because this value is decently close to the comparison value, we can also have a more detailed analysis to this problem to see how different hand motions and actions affect the estimated compressive force. Question: Using the below picture of an endoscopic procedure as a reference, please list the relevant physical task demands for the procedure. An endoscopic procedure involves navigating a tube-like device called an endoscope through a patient’s gastrointestinal tract where a camera is attached at the end to gain visual insight.

Here is another picture of the environment in which the procedure is performed for additional context. Answer: Force: ● The doctor must apply a constant force equal to the mass of the endoscope times the acceleration due to gravity throughout the exam in order to hold up the endoscope. ● The doctor’s positioning is causing a force on their lower body as they are standing throughout the exam. Repetition: ● The hand/fine motor movements to do with adjusting and moving the endoscope are continually repeated throughout the procedure.

Contact/Mechanical Stress: ● While there is a gap between the part of the device the doctor looks into and their eye, it is certainly valid to assume that there is frequent contact, even if accidental, resulting in force applied near the eye region. Awkward Posture: ● There is neck flexion at an angle far greater than the 15 degrees that would be considered comfortable. Environmental Factors: ● The procedure is often performed at a hospital. Operating/examination rooms often feature bright, acute lights for precise illumination. ● Hospitals are also kept fairly cold to control for humidity and bacterial growth. This answer requires outside information. Question: What is the role of risk assessment in human-centered design, improving task safety and tool usability? Moreover, what does it tell us about the relationship between affordance and design? Answer: Risk assessment is a crucial part of the design process as it helps engineers identify and mitigate hazards associated with a system (product or task). It involves evaluating the ergonomic factors within a task and the cognitive aspects of how the task is performed. Finally, the importance of affordances lies in the iterative process of design. We can re-design a tool or task by assessing risks and reducing or avoiding injuries. Group 2 A worker in a ping pong ball factory works an 8 hour shift with two 30 minute breaks scheduled in. They must squeeze each ping pong ball that comes off the assembly line to check that there are no leaks. The worker squeezes 10 balls with a pinch grip every 17 seconds, with each squeeze lasting 1 second. There is 15º of wrist extension during the squeeze. The worker has been performing this job for 11 years, and rates their exertion as a 2/10. Is this task dangerous for the worker? (HINT: use the Revised Strain Index) ANSWER: RSI with I = 0.2, E = 35.3, D = 1, P = 15º extension, h = 7

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IM = 2.62 (from table) EM = 0.1+0.25(E) = 8.9 DM = 0.76 (from table) PM = 1 (from table) HM = 0.042(H) + 0.09ln(H) + 0.477 = 0.95 RSI = 16.84, this task is VERY dangerous for the worker as the RSI > 10 Group 3: What research questions can be answered using motion capture analysis technologies (circle all that apply)? a. how fast is the movement required of the task? b. the amount of force exerted on the limbs throughout the task c. how long are certain positions held throughout the task? d. the joint angles throughout the task e. all of the above answer: a, c, d What kind of grip is strongest and can exert the most amount of force? a. power key b. hook grip c. power grip d. pulp-to-pulp prehension pinch answer: c Group 4: As an industrial designer, you have been tasked to design a tennis racket that minimizes the risk of injury and fatigue during gameplay. Your task is to analyze the physical demands of a tennis-related task and determine the maximum endurance time and suggested recovery time for the task. Task description: The task is to hit a tennis ball using a racket with a force of 50 Newtons. The individual has a maximum Voluntary Contraction (MVC) of 152 Newtons for their biceps.

Question: What is the individual’s maximum endurance time and suggested recovery time for hitting a tennis ball with a force of 50 Newtons? Assumptions and additional information: ● Assume the player is hitting the ball with the correct technique to minimize the risk of injury and fatigue. ● The player has an average fitness level and no pre-existing injuries. ● The tennis racket is of standard size and weight. ● Recovery time refers to the time required for the muscles to recover from fatigue and injury. ● Consider any other factors that may affect the player's endurance and recovery time. Solution: The task is to hit a tennis ball using a racket with a force of 50 Newtons. The individual has a maximum Voluntary Contraction (MVC) of 152 Newtons for their biceps. ((50N)/(152 N))*100 = 32.89% MVC 33% MVC has endurance of 2.0 min 2.0*60seconds/min = 120 seconds 33% MVC at 120" requires 800% or 8 times 120" in recovery time

120*8=960 seconds 960 seconds/(60seconds/min)=16 min. Group 6: How do exposure and risk relate/differ? A. They are synonymous concepts that describe events with awkward posture, high force, repetition, and psychological demand. (CommonMSD pg 24) B. Hazardous exposures will necessarily lead to risks in work. C. Lower back injury exposure and risk can be measured by Revised NIOSH Lift Equation, and upper extremities by Revised Strain Index. (Risk Assessment Design) D. Exposure to force, repetition, duration of exertion and posture are risk factors used in the calculation of risk assessment. (Risk Assessment Design pg 30) The option D is correct. A is wrong because the definition is only for exposure. B is wrong because with appropriate intervention, safe work space can be achieved even when exposures can be present. C is wrong because the assessment tools are only for measuring risk, not exposure. Mark ALL of the following that muscle force production is NOT influenced by: 1. Muscle fiber type 2. Age 3. Height and weight 4. Number of motor units activated 5. Velocity & Type of Contraction Answer: 2, 3 do NOT influence muscle force production Content: Week 3 slide 7 Difficulty: 5/10 (I struggle with mark ALL that are NOT because of the wording of the questions is tricky) Question: If the RWL is less than the actual weight of the object to be carried, what does this indicate and what need to be done in order to fix this?

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Answer: This indicates that lifting this object would be unsafe for the majority of workers. We must reduce the amount of control needed at the destination be redesigning the object or process of lifting said object. Two sample MCQs: 1. Which of the following is NOT a component of the Revised Strain Index (RSI)? A. Force B. Repetition C. Posture D. Temperature Correct answer: D. Temperature. The Revised Strain Index assesses the ergonomic risk associated with job tasks by evaluating the force, repetition, posture, and duration of exposure, but temperature is not considered a component of RSI. 2. Which of the following best describes the Revised Strain Index (RSI)? A. A tool for assessing the ergonomic risk associated with a job task B. A measure of the amount of stress experienced by an individual C. A method for evaluating the physical demands of a job task D. A technique for analyzing the financial impact of workplace injuries Correct answer: A. A tool for assessing the ergonomic risk associated with a job task. Group 7: Understanding and applying new content always has its challenges. One way to facilitate learning is for you to have to teach, or test, someone else on the material. Therefore, for this assignment, you will write a midterm exam question and answer. Please respond to this discussion by posting your question and the correct answer. If you are writing a multiple choice question, please provide all possible answers including the correct one AND indicate which answer is correct. We will check the questions and answers and "like" the ones that we think are clear, concise, accurate and appropriate given the content provided. At least one question will be included in the actual exam. Please see the rubric below for the grading structure.

GRADING CRITERIA POINTS Question relates to the content provided thus far 10 points Question is clearly written 10 points Level of difficulty is appropriate 10 points Answer options are plausible 10 points Correct answer is provided 10 points Midterm Exam Question: John is debating whether to train for a speed triathlon or continue recreational biking on his cruiser. In his decision, he would like to know the ergonomic costs of triathlon biking compared to recreational cruising biking. You have been hired as an ergonomics consultant to analyze his form in each mode. You have taken photos of his form in sport mode, seen below for your reference. a) Find his REBA score of the sports mode to determine the risk involved?

b) Why could competitive biking be more risky than recreational biking? Select all that apply. A. Higher risk of crashing for competitive biking B. Trunk is bent at a larger angle in competitive biking C. Neck orientation is closer to neutral in recreational (upright cruiser) biking D. Biking recreationally (cruiser style) is more taxing in the long-term E. Repetitive motions are done at a higher frequency in competitive biking NOTE: Show c) only after answering b) c) With these improvements in mind, calculate the new REBA score of recreational biking with ideal posture. An example is shown for your reference

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d) What decision would you recommend to your client? Answers: a) Final REBA Score: 9 (see working) b) A, B, C, E c) Final REBA Score: 4 (see working) d) Remain in recreational (cruiser style) biking as the cost of sports style is too high Group 8: A worker at a car factory is responsible for securing the hood of the car onto the vehicle. He takes the hood, and then presses down while another worker drills the hood on. The worker has been experiencing wrist pain as of late, and we want to measure the RSI of the task. The worker estimates he uses a force of 5 out of 10 on the Borg CR-10 scale, places one trunk per minute, takes around 20 seconds to place the trunk, has a 45-degree flexion in his wrist, and works 8 hours per day. What is the RSI for this workers job? A) 9.75 B) 22.40 C) 24.95

D) 14.35 Correct Answer: C Q) A 200-pound man stoops over such that his back is parallel to the floor to pick up a 20- pound load. The horizontal distance between the load and his lower back is 15 inches. What is the estimated compressive lumbar force? Which component has the biggest value? A) BW = 200 lb L = 20 lb HB = 15” Theta = 90 Sin Theta = 1 A = 3 * 200 * 1 = 600 B = 0.5(20*15) = 150 C = 0.8 ((200/2)+(20)) = 86 Total = 846 lb The highest term comes from the back posture. When analyzing injuries, there are two main injury mechanisms. Sudden Force, or Volitional Activity. These two injury mechanisms result in their own categories of injuries, being Impact trauma, and overuse, respectively. Given that you have thankfully not had any sudden injuries, you’re not as concerned over sudden force injuries, resulting in impact trauma. Given that you are interested only in overuse injuries, please only select those that may result from an overuse injury. ● Nerve entrapment

● Low Back Pain ● Contusion ● Joint subluxation ● Myofascial pain Q: Using the University of Utah Back Compressive Force estimate estimation, what is the compressive force of a person weighing 150 pounds, carrying a load of 30 pounds, to a horizontal distance of 18 degrees? A: 804 pounds Group 9: Reaching down to touch your toes would cause _________ in the __________plane. a. Hyperextension; Sagittal b. Flexion; Sagittal c. Flexion; Frontal d. Hyperextension; Frontal Correct Answer: B Group 11: You are an industrial engineer trying to determine the total shoulder moment for a 180 lb worker lifting a 50 lb load that is 15 inches away from their shoulder (horizontal distance from shoulder to load). Answer the following based on the above information. 1. What is the total shoulder moment? (approximately) 1. 420 lbs (406 lbs ((15*25) + (0.0115*15*180)) 2. 781 lbs 3. 231 lbs 4. None of the above 2. Is this higher or lower than the criterion moment? 1. Higher (406 in-lbs > 270 in-lbs) 2. Lower

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3. Insufficient information *answers are bolded What does Taylor’s principle encompass? A) Arranging a hierarchical organization B) Dividing work in small separate and unique tasks C) Training workers to work efficiently in one best way D) All of the above Group 12:

Table 26, Mital & Kumar (1998): Mean and standard deviation of a 2.0cm chuck pinch (based on data from 17 males): 16.9 kgf, 7kgf *Conversion Factor: 1kgf = 9.8 N Part A) Calculate the maximum acceptable force for a 50th percentile, 60-year-old male performing 2.0-centimeter chuck pinches using the following data: 1. Exertion duration: 1.0 second 2. Frequency: 2000 efforts per shift 3. Shift length: 8 hours Assumptions: ● Table 26 is based on healthy, 24-year-old males at full strength exertion capability

● Write your answer in N. Part B) How much would it change if you designed for a 25th percentile, 24-year-old female? Solution Part A: ● MAE Frequency (Exertions/Minute) = 2000 efforts per shift / 8 hours * 1 hour/60 minutes ○ = 4.17 exertions/minute ● Duty Cycle (%) = 4.17 exertions/minute * 1 second/exertion *1 minute/60 seconds ○ = 6.95% ● MAE = 1 - (DC – 1/3600) ^0.24 ○ = 1 – (0.0695 – 1/3600)^0.24 ○ = 0.473 ● Max Strength = (Mean - Z-score* Standard Deviation) * % Strength Exertion Capability (60 year old man) ○ = (16.9kgf * 9.8N/kgf – 0) * 0. 75 ○ = 124.22 N ● Max Acceptable Force = MAE * Max Strength ○ = 0. 473* 124.22N ○ = 58.756N Part B: The same calculations for MAE; Max. strength calculations change due to changes in percentile, age, and gender. ● Max Strength = (Mean - Z-score* Standard Deviation) * % Strength Exertion Capability (24 year old female) ○ = 0.62 * (16.9 kgf * 9.8N/kgf – 0.67 * 7.0kgf * 9.8N/kgf) ○ = 74.188N ● MAE = ○ 0.473 (from part A) ● Max Acceptable Force = MAE * Max Strength ○ = 0. 473* 74.188N ○ = 35.09N Group 14:

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Problem: Consider the following scenario: Sarah works in a warehouse where she is responsible for moving heavy boxes from one location to another. The boxes weigh anywhere between 50-70 pounds, and she has to lift them from the ground – usually done so by bending over – onto an elevated trolley and move them several times a day. Sarah has been working in this position for several months now and has noticed that she is experiencing pain in her back and shoulders. She has also noticed that her colleagues who work in similar positions are experiencing similar problems. They have all been taking pain medication to manage the pain, but this has not helped them in the long run. What aspects of this scenario should be redesigned to minimize Sarah and her colleagues’ back pain? Choices: a. Task b. Equipment c. Environment of Work Station d. All of the above e. None of the above Solution The correct answer is D . This is because - Task Redesign: Instead of bending over, she should bend down with her knees to lift the boxes. She could also implement mechanical assistance, to help lift the boxes onto the trolley (this also contributes to equipment redesign). - Equipment Redesign: There are ways to improve the task by having ergonomic tools to make the task easier. For example, lift tables can help reduce the strain on the back while lifting and moving heavy boxes. Having anti-fatigue mats to lessen the legs and the foot also helps since the workers are standing for long periods of time. - Environment Redesign: All the workers need to move heavy boxes from the floor to an elevated surface. The workplace can implement adjustable workstations to maintain proper posture and reduce the risk of musculoskeletal disorders.

Group 17: Which is NOT a Physical Risk Factor for Musculoskeletal Disorders? ● Repetition ● Awkward Posture ● Environmental: Vibration, Temperature, Lighting ● Sudden Force <- Correct Answer A chocolate factory worker cranes his neck downwards to pipe fine chocolate details. What REBA neck position is the worker most likely in? 1. 50 flexion sagittal 2. 50 flexion transverse 3. 50 exterior transverse 4. 50 exterior sagittal ANSWER: 50 flexion sagittal Which factor does NOT lead to adding a point to the REBA assessment? A. 1 more body part being held for longer than a minute B. Quick and sudden changes that happen once in a while C. Repeated small-range actions (more than 4x per minute) D. Actions causing rapid large-range changes in posture or unstable base (Correct answer highlighted ) Bob’s job is mainly static and lifts less than 4.4lbs. They have their upper arms in 20° of extension with no support and lower arms are working across the midline of the body. Their wrist is 16° of flexion, is bent, and twisted in midrange. Their neck is 15° in flexion with no twist or bend. Their trunk is 10° in flexion with no twist or side bend. Their legs are not supported. What is their final score according to RULA? Final Score: 3

Below are some descriptions of NIOSH Lifting Index, choose the wrong statement: a. Load constant is 23 kg. b. The higher RWL is, the safer the job is c. LI needs to be calculated before calculating RWL. d. Lifting closer to the body is safer than lifting further from the body. Answer : C. Correct procedure is: Observe task -> Determine task variables -> Compute Multipliers -> Compute RWL -> Compute LI Alex is a 150 lb factory worker who carries unit loads of 25 pounds. For the job, they are frequently bending down to pick up and transfer these loads. His current task requires

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him to bend 3/4 of the way from standing, vertical position, carrying loads at a distance of 18 inches from his hands to his lower back. Using the University of Utah back compressive force estimate, estimate the total lumbar compressive force acting on Alex. Round to the nearest tenth if applicable. Correct Answer: 691.6 (exact) Other correct answers: would take correct answers within range of 691.6-700.8 to account for students who used the full value for sin(67deg) in their calculation, rather than the provided .9 Group 18: Using the below values, calculate the REBA score. Which of the following is true? Right Arm: Upper Arm Position: 40 degrees Unsupported, shoulder not raised, upper arm not abducted Lower Arm Position: 90 degrees Wrist Position: Neutral Power Grip and Reasonable Handle Neck Position: 20 degrees Trunk Position: 47 degrees Legs: 55 degrees Load is > 22lbs Non static, large changes in posture. a. REBA score = 6; this is a medium risk task b. REBA score = 6; this is a high risk task c. REBA score = 7; this is a medium risk task

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d. REBA score = 7; this is a high risk task e. REBA score = 8; this is a medium risk task f. REBA score = 8; this is a high risk task Answer: Neck Score: +2 Trunk position: +3 Legs: +1 Posture Score A: 4 Force/Load Score: 2 Score A: 4 + 2 = 6 Upper Arm: +2 Lower Arm: +1 Wrist: +1 Posture Score B: 1 Coupling Score: 0

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Score B: 0 + 1 = 1 Activity score: +1 Score A = 6, Score B = 1, Table C score = 6. Final REBA Score = 6 + 1 = 7. This is a medium risk task. (c) is correct. Group 22: Think about the action of a person lifting up a heavy box. What plane(s) of the body is the person moving along while performing this action? What kind of concurrent exposures should you consider when assessing how this task may affect the person long term? Answer: The person is moving along the sagittal and frontal planes. I would be concerned about repetition and force resulting from the weight of the box. Two simpler questions: Where does the revised strain index pertain to? What important related task does it not cover? It covers the upper extremities, but does not work on typing/computer tasks What percentage of the female population should accept a recommended weight limit (RWL) task? a: 99% b: 85% c: 75% d: 50%

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When an individual is holding a bowel of soup in the palm of their hand while walking. Which of the following best describes the position of the hand when conducting this movement: A.Pronation B.Flexion C.Supination D.Two of the above Correct Answer: C. Supination Group 23: Question: Explain at least 2 different risk assessment tools. Possible Explanation: NIOSH Lift Equation - estimates the risk of low back injury. Examines variables such as object weight (w), horizontal location of hands (H), vertical location of hands (v), object vertical travel distance (d), asymmetrical angle (a), hand coupling (c), frequency of lifting (f) and task hours per day (hr). In combination with the use of tables to get multipliers, the values are used to calculate a recommended weight limit (RWL). The lifting index (LI) is then calculated by the ratio of object weight to the RWL. An LI<1 is protective, LI>=1 and <2 may poses risk to some workers, LI>=2 and <3 poses a significant risk to many workers, and LI>= 3 is a significant risk to most workers. Rapid entire body assessment (REBA) - a final REBA score is used to assess the level of risk of a task and the urgency for which action should be taken. This assessment examines the employee's neck, trunk and leg position to get a total posture score. Arm and wrist analysis is done to get another posture score. Force/load and coupling and added to each respectively before using those values to be a combined score from table c. This is added with an activity score to obtain a final REBA score. A score =1 is at negligible risk, 2 or 3 at low risk, 4 to 7 medium risk, 8 to 10 high risk, and 11+ is a very high risk activity.

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Midterm practice quesions from each group

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