The Evaluation Effect of AwkwardPosture on the Performance of the Musculoskeletal System

IE342 – Human FactorStudents: Khadija Mughrbil 1333162Heba Gogandy 1334978Instructor: Eng. Wafa

The Evaluation Effect of Awkward Posture on the Performance of the Musculoskeletal SystemFaculty of Engineering-girl’s campusLab 6 – IE342

Table of ContentsIntroduction..............................................................................................................................2Objectives.................................................................................................................................2Instrument................................................................................................................................3Experiment Procedures............................................................................................................3Results of the Experiment........................................................................................................4ANOVA test...............................................................................................................................7Mean, standard deviation and percentile..................................................................................8Conclusion................................................................................................................................8

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The Evaluation Effect of Awkward Posture on the Performance of the Musculoskeletal SystemFaculty of Engineering-girl’s campusLab 6 – IE342

INTRODUCTION

This lab report will discuss how wrong working postures or an awkward working posture can

affect the worker and the work, in many different ways. Awkward posture is one of the most

important factors that lead to musculoskeletal disorders as well as a heavy physical workload.

Ergonomics defines the term ‘awkward posture’ as a deviation of a joint from the preferred

neutral position, in other word, performing a task with different body parts (e.g., back, joints)

twisted or bent backward or forward rather than in the neutral position (the normal position of

body parts), causing transient discomfort and fatigue. Awkward posture is the result of a

mismatch between the workplace design and the dimensions of the human body and can lead to

musculoskeletal problems, particularly lower back disorders.

Various methods and techniques are used to evaluate the impact of awkward posture on the

performance of the musculoskeletal system. These methods are divided broadly into two types:

Firstly objective measures of performance, physiology (e.g., heart rate, muscles activity, blood

pressure) and force on body parts; and secondly assessment tools for subjective measures,

including the Rapid Upper Limb Assessment Tool and this is what is used in this lab. RULA is

one of the most common methods used to evaluate the musculoskeletal risks of poor posture in

upper body parts, particularly the neck, trunk and upper limbs. This method easily calculates the

rating of musculoskeletal loads in tasks that present a risk of neck and upper-limb loading. This

report will represents the objective, instruments used, procedures of the experiment, results and

conclusion.

OBJECTIVESThe objectives of this laboratory experiment are as follows:

1. To gain knowledge about awkward postures

2. To learn about common methods (performance, physiological and subjective) used

to assess the effect of awkward posture on the musculoskeletal system and its

performance

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The Evaluation Effect of Awkward Posture on the Performance of the Musculoskeletal SystemFaculty of Engineering-girl’s campusLab 6 – IE342

3. To understand how to implement the RULA method as a common technique to

assess musculoskeletal risks while performing a task

4. To learn how to compare the musculoskeletal risks of two different working postures and to educate students about musculoskeletal risks posed by these working postures

INSTRUMENTA wooden plate and two uprights have small wooden plates with 12 bolts for each upright plate

and each bolt has nuts and washers (see Figure 1).

The wooden plate simulates the assembly task because this type of task is common in many

different factory jobs, particularly in the industrial sector, and the operator can assume an

awkward posture to perform this type of task. Two types of hand tools (10-inch Crescent

wrench and screwdriver) are used to fix the bolts to the wooden plate. In addition a mobile

application (Heart Rate) used to measure the heart rate.

Figure 1 the wooden plate

EXPERIMENT PROCEDURES The experiment procedures are as follows: 1. Participants are given a brief introduction to the experiment in order to familiarize them with the procedure.

2. They are provided with instructions and advise on how to assemble the wooden plates.

3. The participants are then asked to take the records of their heart rate at resting level and at the end of each minute while performing the assembly task.

4. Next the participants start the assembly task in three different postures (three conditions): first at standing posture, secondly at sitting posture in the neutral posture and thirdly at awkward posture in which the back is leaned forward without the knee bent. In each posture

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The Evaluation Effect of Awkward Posture on the Performance of the Musculoskeletal SystemFaculty of Engineering-girl’s campusLab 6 – IE342

the participant needs to fix 12 bolts on both upright plates (see Figure 1) within the 5 min of allotted time.

5. The accuracy and the actual time required to complete the task are recorded.

6. Finally immediately after completing each condition in the 2- to 3-minute break between each task condition, the participants are asked to complete the Borg-CR10 scale (see Figure 2).

0 Nothing at all “No P”0.30.5 Extremely weak

Just noticeable1 Very weak1.52 Weak Light2.53 Moderate45 Strong Heavy67 Very strong8910 Extremely strong “Max P”11ϟ

● Absolute maximum Highest possible

Figure 2 Borg-CR10 rating scale range

RESULTS OF THE EXPERIMENTThe heart rate, RULA assessment and Borg assessment of the participant is shown below for the standing, sitting and awkward postures:

Standing posture

Table 1 standing posture heart rate

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Time/min Heart rate/

0 641 712 683 754 68

The Evaluation Effect of Awkward Posture on the Performance of the Musculoskeletal SystemFaculty of Engineering-girl’s campusLab 6 – IE342

Figure 2 standing posture RULA sheet

The participant used the Borg range and ranked the task as extremely weak just noticeable.

Conclusion of standing posture: The average heart rate 69.2 bpm. The risk of the task according to the RULA sheet is 2 which means that the posture is acceptable.

Sitting posture

Table 2 sitting posture heart rate

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Time/min Heart rate/0 601 642 633 694 65

The Evaluation Effect of Awkward Posture on the Performance of the Musculoskeletal SystemFaculty of Engineering-girl’s campusLab 6 – IE342

The participant used the Borg range and ranked the task as nothing at all.

Conclusion of standing posture: The average heart rate 64.2 bpm. The risk of the task according to the RULA sheet is 3 which means that the posture is acceptable.

Awkward posture

Table 3 awkward posture heart rate

Time/min Heart rate/0 611 742 743 76

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Figure 3 sitting posture RULA sheet

The Evaluation Effect of Awkward Posture on the Performance of the Musculoskeletal SystemFaculty of Engineering-girl’s campusLab 6 – IE342

4 73

Figure 4 awkward posture RULA sheet

The participant used the Borg range and ranked the task as moderate task.Conclusion of standing posture: The average heart rate 71.6 bpm. The risk of the task according to the RULA sheet is 4 which means that the posture is somehow acceptable and may need some improvements.

ANOVA TESTIn order to determine if there is significant deference between the three postures, the team conducted the ANOVA test as shown in figure 5, with H0: µ1= µ2 =µ3 and H1: µ1≠ µ2≠ µ3

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The Evaluation Effect of Awkward Posture on the Performance of the Musculoskeletal SystemFaculty of Engineering-girl’s campusLab 6 – IE342

From the results of the ANOVA test, the P value is 0.077 which is greater than α (0.05). This means we cannot reject H0 and we conclude that the three postures does not have significant difference.

MEAN, STANDARD DEVIATION AND PERCENTILEThe mean and standard deviation of each posture is shown in table 4 below:

Table 4 Mean and Standard deviation

0 1 2 3 4 Mean Standard deviationP1 64 71 68 75 68 69.2 4.08656P2 60 64 63 69 65 64.2 3.27109P3 61 74 74 76 73 71.6 6.02495

To calculate the percentile, the formula X=μ + Zσ will be used to find the 5th, 50th, and 95th percentile. The following table shows the calculations:

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The Evaluation Effect of Awkward Posture on the Performance of the Musculoskeletal SystemFaculty of Engineering-girl’s campusLab 6 – IE342

Table 5 Percentile

5th 50th 95thX (P1) 62.47761 69.2 75.92239X (P2) 58.81906 64.2 69.58094X (P3) 61.68896 71.6 81.51104

CONCLUSIONThis was the sixth lab report, and it discussed the effect of awkward posture on the performance of the musculoskeletal system. The evaluation methods used are divided broadly into two types: Firstly objective measures of performance, physiology (e.g., heart rate, muscles activity, blood pressure) and force on body parts; and secondly assessment tools for subjective measures, including the Rapid Upper Limb Assessment Tool (RULA) and Borg assessment. This lab report represented the objective of this experience, the instruments used, experience procedures, results of the experiment and finally concluding of results.

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