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 Table of Contents  
ORIGINAL ARTICLE
Year : 2019  |  Volume : 9  |  Issue : 2  |  Page : 135-142

Ergonomic posture analysis of different postures in laptop users at non-official places and related musculoskeletal disorders by rapid upper limb assessment method


1 Research Center for Environmental Pollutants, Department of Occupational Health, Qom University of Medical Sciences, Qom, Iran
2 Student Research Committee, School of Health, Qom University of Medical Sciences, Qom, Iran
3 Neuroscience Research Center, Department of Epidemiology and Biostatistics, Qom University of Medical Sciences, Qom, Iran

Date of Web Publication8-May-2019

Correspondence Address:
Abolfazl Mohammadbeigi
Neuroscience Research Center, Sholl of Health, Qom University of Medical Sciences, Qom
Iran
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/AIHB.AIHB_85_18

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  Abstract 


Background: Laptops are not ergonomically being designed as the same as a desktop computer and are not suitable for prolonged use. The current study aimed to assess the different postures laptop users, especially in non-official places, and its effect on musculoskeletal disorders (MSDs). Study Design: This was a cross-sectional study. Methods: One hundred and fifty university students were chosen that have continuous use of laptop for 5 years. Data were gathered by questionnaire (demographic data, laptop use-related questions and visual posture questions) and posture analysis using Rapid Upper Limb Assessment method. T-test, Chi-square and Spearman correlation coefficient tests were used in data analysis. Results: The mean of body weight in males and females was 77.58 ± 13.34 kg and 62.35 ± 10.67 kg, respectively. Two postures, including E (sitting on the sofa and put the laptop on the table) and F (sitting and working on an office chair and desk), were the most current postures by the users. Postures M and K had been as the most inappropriate postures, while postures D and G were defined as postures that are more appropriate. Conclusion: Laptop is using frequently as a popular device at home, dormitory or other non-official places. Due to nature of these places and inherent characteristics of laptops, it is not possible to make it adjust for the body based on ergonomic principals. Neck, upper and lower back, shoulder and wrist are organs that influence more by laptop based on body configuration.

Keywords: Ergonomic postures, laptop user, musculoskeletal disorders, Rapid Upper Limb Assessment


How to cite this article:
Heidari H, Soltanzadeh A, Asemabadi E, Rahimifard H, Mohammadbeigi A. Ergonomic posture analysis of different postures in laptop users at non-official places and related musculoskeletal disorders by rapid upper limb assessment method. Adv Hum Biol 2019;9:135-42

How to cite this URL:
Heidari H, Soltanzadeh A, Asemabadi E, Rahimifard H, Mohammadbeigi A. Ergonomic posture analysis of different postures in laptop users at non-official places and related musculoskeletal disorders by rapid upper limb assessment method. Adv Hum Biol [serial online] 2019 [cited 2019 Aug 18];9:135-42. Available from: http://www.aihbonline.com/text.asp?2019/9/2/135/257822




  Introduction Top


Nowadays, the development of technology along with the need to access information has resulted in use of personal computer to be inevitable.[1],[2] However, the nature of working with computer in one hand and does not paying attention to occupational health and their ergonomics principles during the work and prolong time spent with the computer, on the other hand, have led to the high prevalence and serious musculoskeletal disorders (MSDs) in computer and laptop users.[2],[3] The use of computers is growing quickly. Advances in technology and microprocesses, battery technology and increased storage capacity led to creating the small portable computers, which are lightweight means and capable of processing similar to desktop computers. Simultaneously, beside the improvement in the technical characteristics of laptops, much effort has been done to achieve ergonomically satisfactory laptop designs.[4] Many studies were done on the posture analysis of operators with visual display terminals (VDTs) and the prevalence of their MSDs. Most of them performed in official places.[5],[6],[7] However, a few studies have comprehensively evaluated laptop users in real and current conditions in non-official places, for example, at home.[8],[9]

Despite the advantages mentioned on the laptop, use of these devices associated often with considerable musculoskeletal risks for their users.[10] Based on ergonomic principles, laptops are not ergonomically designed the same as a desktop computer, and it may not be suitable for prolonged use.[4]

Due to the inherent portability of laptops, users especially in non-official places are applying these devices in different postures, that some of them are unfavourable situations in terms of ergonomics basis. These situations include lie down on the ground or on a bed; sitting posture with a difficult situation on the furniture, chairs or on the ground; work with laptop on unspecified desk, etc. Awkward postures during prolong use of laptop will cause irreversible and chronic disorders in pressurised organs.[11],[12]

Many efforts have been made to determine the optimal VDT screen height regarding MSDs of the shoulder and neck region and visual strain. However, it may be in conflict to reduce MSDs while also reducing visual strain and the feasibility of these remains debatable.[13],[14]

Since laptops are designed to be movable, they are applied in a wide variety of configurations, some of which may encounter the user with risk of injury.[8] In a survey was conducted among laptop users aged 19–30 years, 77.3% of participants reported having discomfort in the neck, forearm, arm, wrist and shoulder after continuous work with laptop. The neck complaints were the highest percentage with 60.3%. Similar results have obtained in several studies, and the relation between neck and upper extremity strains and working with VDT have proved.[7],[15],[16],[17] Although some ergonomic interventions such as adjustable laptop stations or desks have introduced and effectiveness of them to decrease musculoskeletal strains, especially neck and shoulder discomfort have confirmed,[14],[18] they are not always available for all groups of people and their utilisations are unknown. Therefore, it is expected that in non-official places for example, at home, on bed, etc., the laptop users will be in riskier postures than others who work in official places. Therefore, in this study, current postures of laptop users and related musculoskeletal complaints in the non-official places were studied for identify the following purposes: (a) identify the more frequent postures took by laptop users in non-official places; (b) determination the prevalence of MSDs associated with each chosen posture; (c) posture analysis of each chosen posture and (d) introduce more appropriate and inappropriate postures which taken by users considering related MSDs.

It is expected that the results of this research can be helpful for selecting appropriate postures which have less effect on body organs and create less discomfort. The results also can be used for designing other ergonomic portable laptop stations which are adjustable and applicable for different places and body postures.


  Methods Top


Subjects

One hundred and fifty university students, including 72 males and 78 females aged from 18 to 38 years, were chosen randomly and participated in the study. All of them asked and ensured about the continuous use of laptop from 5 years ago.

Data collection

The required data were gathered across two methods including questionnaire and posture analysis. In the questionnaire part, a researcher-made questionnaire consisting of three parts (demographic data, laptop use-related questions and visual questions) was used. Experts in occupational health and epidemiology were confirmed the validity and reliability of the questionnaire before the study. Demographic data correspond with questions such as age, sexuality, height, weight and dominant hand (right handed or left handed). The second part of the questionnaire, laptop use-related questions, asked questions, for example, about hours per day and week spent usually with laptop, using separate mouse or keyboard during use of laptop, etc., Finally, in the third part of the questionnaire, visual questions, participants selected one or more configuration(s) when using laptop at home or other non-official places. Sixteen pictures of probable configurations of laptop users at non-official places were asked in this section of questionnaire [Figure 1]. Participants determined the frequency of taking each configuration while working with laptop in a six-scale closed question (at all, once a month, several times a month, once a week, several times a week and every day). Moreover, they revealed their discomfort in nine organs of body musculoskeletal system (Based on NORDIC questionnaire), including neck, shoulders, elbows, wrists/hands, upper back, lower back, one or both hips/thighs, one or both knees and one or both ankles/feet. A four-scale answer (negligible, mild, moderate and severe), to determine the severity of the discomfort in each configuration was raised. In posture analysis part, Rapid Upper Limb Assessment (RULA) method was used.
Figure 1: Different configurations of laptop users at non-official places. Description of configurations from A to P: (a) Sitting on two feet without the use of any fulcrum; (b) Lying on a bed with the twisting spine; (c) Sitting on the bed, so that the laptop is placed on an elevated level (pillow); (d) Sitting on the sofa with poor neck posture (no neck support, laptop on foot); (e) Sitting on the sofa and put the laptop on the table; (f) Sitting and working on an office chair and desk; (g) Sitting on the floor and leaning against the wall, and laptop is on foot; (h) Lying in a prone position on the ground and laptop on the floor; (i) Lying in a prone position on the ground with chest support (such as pillow) and laptop on the floor; (j) Lying prone on the floor and put the laptop at higher altitudes (e.g., on a pillow); (k) Sitting on the couch, neck supported with couch handle, and laptop placed on the abdomen and thighs; (l) Sitting on the floor without backrest and laptop located at the higher altitudes (for example, on a pillow); (m) Sitting on the floor without backrest and laptop located on the knee; (n) Sitting on the floor with a backrest and laptop located on legs tucked to the abdomen; (o) Sitting on the floor and leaning on the floor and using a laptop on a table without slope; (p) Sitting on the floor and leaning and using a laptop on a tilt table.

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Posture analysis by Rapid Upper Limb Assessment method

The RULA is an observation posture analysis method, which developed by McAtamney and Nigel Corlett in the University of Nottingham's Institute for Occupational Ergonomics.[19] RULA is a quick survey method for use in ergonomic investigations of workplaces, where MSDs are reported. The RULA method is a screening tool for evaluating biomechanical and postural loading of the body. It is ideal for sedentary workers such as computer workplaces that their work focuses on the neck, trunk and upper limbs. In addition, it can be conducted quickly, so multiple positions and tasks within the work cycle can usually be evaluated without a significant time and effort. The RULA worksheet is divided into two body segment sections on the labelled A and B. Section A covers the arm and wrist. Section B covers the neck, trunk and legs. This segmentation caused that any constrained postures of the neck, trunk or legs could influence the postures of the arms and wrists are included in the assessment. First, the postures' score of Group A (arm and wrist) should be assess and afterward Group B (neck, trunk and legs). For each region, there is a posture scoring scale and additional adjustments outlined on the worksheet which need to be considered and accounted for in the score [Figure 1] and [Figure 2].
Figure 2: Rapid Upper Limb Assessment scoring process.

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The body posture, force and repetition could be assessed by a single-page worksheet. According to this evaluation, for each body region in Section A (arm and wrist) and Section B (neck and trunk), the scores entered. After the data for each region is collected and scored, tables on the form are then used to compile the risk factor variables, generating a single score that represents the level of MSD risk. The final score is acceptable whenever it is either 1 or 2; needs to be investigating further, if it is 3 or 4; needs to be investigating and changing soon, if it is 5 or 6 and needs to be investigating and changing immediately, for the final score of 7.

Statistical analysis

After entering in SPSS statistical software (SPSS Inc., PASW Statistics for Windows, Version 18.0, Chicago, Illinois, USA), the data were analysed using descriptive statistics including mean, standard deviation and frequency. Moreover, to compare the MSDs in different postures and in participants based on demographic characteristics, t-test, Chi-square and Spearman correlation coefficient tests were used.


  Results Top


This study was done on people aging 18–38 years in two groups of males and females. The ranging of body weight of the participants was determined as 50–105 kg (mean ± standard deviation [SD]: 77.58 ± 13.34) and 43–93 (mean ± SD: 62.35 ± 10.67) for the males and females, respectively. The height of the participants was ranging from 155 to 200 (mean ± SD: 173.15 ± 11.95) for the males to 144–190 (mean ± SD: 163.35 ± 8.62) for the females. [Table 1] showed demographic characteristics of the participants and duration of working with laptop in terms of hours in a day and years, separately.
Table 1: Demographic characterisation of the participants

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The results of [Table 2] determined the total prevalence of taking each posture (16 postures) during use of laptop among participants (males and females). In addition, based on duration of continues work with laptop in terms of hours per day and selected postures, the results were shown for both the males and females. From the point of view of prevalence of users' postures during use of laptop in non-official places, the postures of E (sitting on the sofa and put the laptop on the table) and F (sitting and working on an office chair and desk) were the most current postures by users.
Table 2: Total prevalence and frequency rate of taking each posture during use of laptop (n=150)

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The results of posture analysis and obtained RULA scores at each selected posture are summarised in [Table 3]. The results also determined action category of each posture based on RULA assessment method. Based on obtained final score in RULA method [Table 3], postures M and K had maximum value (final score = 7), and these two postures are defined as more inappropriate postures that must be changed as soon as possible to prevent MSDs and discomfort. Accordingly, postures of A, B and L put in the next order (final score = 6). In contrast, postures D and G were defined as more appropriate postures (final score = 3) and postures C, E, F, H, I, O and P put in the second order (final score = 4).
Table 3: Results of posture analysis and rapid upper limb assessment scores at each selected posture

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Musculoskeletal complaints accompanied by taking each posture brought in [Table 4]. Moreover, the relationship between chosen posture and discomfort of each body organs is showed.
Table 4: The incidence and comparison of musculoskeletal disorders in different parts of the body based on the chosen postures

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[Table 5], [Table 6], [Table 7] considered and analysed obtained results in [Table 4] to introduce more appropriate and inappropriate postures among studied postures that can reduce and increase MSDs and complaints, respectively. In addition, as shown in [Table 7], a comparison was made between two evaluation methods in this research, determination of prevalence of MSDs by Nordic questionnaire and posture analysis by RULA method and to compare priority of appropriate and inappropriate postures, as well as common postures detected by both evaluation methods.
Table 5: Order of the appropriate posture based on their effects on the musculoskeletal disorders in different body areas

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Table 6: Order of the inappropriate posture based on their effects on the musculoskeletal disorders in different body areas

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Table 7: Comparison of awkward and appropriate postures determined based on two evaluation methods

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  Discussion Top


Nowadays, laptop transforms to a popular device, especially among young people and university students. On the other hand, some properties such as easy to use, portability and light weighting make it applicable not only in official or occupational places but also for non-official ones such as at the home. The findings of the present study showed that nearly 75% of men and women, which were in young groups, used laptop at home more than 1 h/day (only pleasure times at home). The amounts were 43% for the participants with more than 3-h use and 27% for more than 5-h use. These relations, which were the same for both the men and the women, emphasised that laptop users may be exposed to musculoskeletal risks over the occupational and non-occupational exposures and places.[8]

On the other hand, considering history of continuous work with laptop and age of participants [Table 1], it is indicated that probably laptop is introduced into pleasure times of people after age 18 years or more (nearly aging of university students) and then gradually increased.

The prevalence of users' postures during use of laptop indicated that the duration of laptop use was as a determining parameter to chosen posture. During longer periods, users may adjust their posture and the configuration they are working in.[6] Therefore, postures of B, D, E and L (for men) and C, L and N (for women) were the more current postures, when laptop users worked <1 h. These postures are awkward postures that cannot be maintained for long-term periods. The main reason for this can be neck- and back-induced discomfort resulting from the height of the display, which is normally lower than recommended. In addition, the connection of the display and keyboard can be another reason for upper extremities discomfort.[20],[21]

As the same way, postures of N, O and F (for men) and F, C and I (for women) were more repeated postures for working duration of 1–3 h. In fact, in postures of O and F, laptop locates directly on a table and in postures of N and C, the laptop status is so that the eye height is somewhat corrected by the users. In another study among laptop users (n = 300), 28.7% (86 participants) took postures similar to postures of G, L, C and M (generally sitting on the floor and put the laptop on the legs) and 24% (72 participants) took postures similar to posture of F (use a laptop on an official desk).[15] However, the posture of I was one of the worst and inappropriate postures which taken usually by the women more than men. For continuous 3–5 h working with laptop, current and more selected postures were E, I and M (for men) and E, L and F (for women). This finding revealed that probably women keep their body in normal status more than men during continuous work or long times either by locating laptop on a table or by correction of eye height. For continuous working more than 5 h, both of the men and women chosen rather ergonomic and appropriate postures (O and F) to diminish musculoskeletal discomfort. Similar to our findings, it is indicated in other studies that small changes in posture, especially those of the head and neck which tend to be more static, can have a considerable effect on comfort and the risk of MSDs over long periods of exposure.[4],[12],[22]

According to the results of posture analysis, postures M and K defined as more inappropriate postures that must be changed as soon as possible to prevent MSDs and discomfort. Neck, back and wrist are experienced inappropriate situation in these configurations. Postures of A, B and L put in the next order (final score = 6). In contrast, postures D and G were defined as more appropriate postures (final score = 3) and postures C, E, F, H, I, O and P put in the second order (final score = 4). Consistent with our findings, neck, wrist and shoulder were determined in another study as more prevalent organs considering MSDs.[15]

Taking different body postures during use of laptop can engage different parts of the musculoskeletal system, so that, in some cases such as posture I, all of nine of studied body organs influenced and participants experienced pain and discomfort in these regions [Table 4]. Either since the importance of the presented results in this table to introduce most appropriate or inappropriate postures from several body statuses studied in this research, it is necessary to argue in detailed through the complementary next tables. Therefore, as shown in [Table 5], the MSDs induced by postures H, B and E were less than other ones. In other words, the related posture categories of these postures were 8 (i.e., based on discomfort and sensed pain by the participants, these postures had least effect in 8 of 9 of studied regions of musculoskeletal systems). The only exception was in the case of elbow. It means that these postures have more impact on elbow.

Posture of O with posture category of 6 locates on next priority. Other priorities detected in [Table 5] by details. On the other hand, as presented in [Table 6], postures I (Lying in a prone position on the ground with chest support) and then M (Sitting on the floor without backrest and laptop located on the knee) were determined as worst body status considering damage of musculoskeletal system. In these configurations, the neck must be tolerated more mechanical load on cervical joints. Similar results have obtained in several studies.[5],[13],[14]

Comparison of the appropriate and inappropriate postures determined in this study by two evaluation methods (posture analysis by RULA and questionnaire survey by NORDIC) showed that the most inappropriate postures are I and M, respectively. Based on the obtained final score in RULA method, postures of M, K, A, B, L, J and N were selected in three first priority by the participants. Regardless of determined priority, postures of M, L, J and N identified as awkward postures in both of the assessment techniques. Similarly, postures of H, E, D, O and C were determined as more appropriate postures in this investigation. It should be mentioned that these postures were not the most appropriate postures based on ergonomic principles, necessarily (these were more appropriate postures from the current postures chosen by the participants in this study). The studies of the more current postures were taken by the laptop users can be introduced as a limitation of this study. It is strongly recommended that some other studies may be needed by other postures to verified appropriate and comfortable postures for laptop users in non-official places.


  Conclusion Top


Based on our results, postures M; Sitting on the floor without backrest and laptop located on the knee, and K; Sitting on the couch, neck supported with couch handle and laptop placed on the abdomen and thighs were defined as more inappropriate postures, and emergency changes are required for preventing of MSDs. In contrast, postures D; Sitting on the sofa with poor neck posture (no neck support, laptop on foot) and G; Sitting on the floor and leaning against the wall, and laptop is on foot were defined as more appropriate postures. Based on our analysis, postures I (lying in a prone position on the ground with chest support) and M (sitting on the floor without backrest and laptop located on the knee) were determined as worst body status considering damage of musculoskeletal system. Moreover, neck, upper and lower back, shoulder and wrist are organs that influence more by laptop based on body configuration.

Declaration of patient consent

The authors certify that they have obtained all appropriate patient consent forms. In the form the patient(s) has/have given his/her/their consent for his/her/their images and other clinical information to be reported in the journal. The patients understand that their names and initials will not be published and due efforts will be made to conceal their identity, but anonymity cannot be guaranteed.

Acknowledgement

The authors are very grateful for research Vice-Chancellor of Qom University of Medical Sciences with Grant Number of 95725, as well as all subjects who participate in the study.

Financial support and sponsorship

This study was financially supported by Qom University of Medical Sciences.

Conflicts of interest

There are no conflicts of interest.



 
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  [Table 1], [Table 2], [Table 3], [Table 4], [Table 5], [Table 6], [Table 7]



 

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