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PLoS One. 2018 Aug 30;13(8):e0203394. doi: 10.1371/journal.pone.0203394. eCollection 2018.

Ergonomic risk assessment of smartphone users using the Rapid Upper Limb Assessment (RULA) tool.

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Research Center in Back, Neck, Other Joint Pain and Human Performance (BNOJPH), Khon Kaen University, Khon Kaen, Thailand.
School of Physical Therapy, Faculty of Associated Medical Sciences, Khon Kaen University, Khon Kaen, Thailand.
Program of Production Technology, Faculty of Technology, Khon Kaen University, Khon Kaen, Thailand.
Department of Environmental Health Science, Faculty of Public Health, Khon Kaen University, Khon Kaen, Thailand.
School of Health Sciences (Physiotherapy) University of South Australia, iCAHE (International Centre for Allied Health Evidence), Adelaide, Australia.


The number of smartphone users globally is rapidly increasing. This study aimed to assess the level of ergonomic risk to smartphone users, and to evaluate the correlation between any self-reported musculoskeletal disorders and the level of ergonomic risk. Thirty participants completed a questionnaire, tailored specifically for smartphone users, to determine any musculoskeletal disorders. Participants were given a seated smartphone texting task and their postures were video recorded during the task. The video scenarios were evaluated by three independent researchers to determine the level of ergonomic risk using the Rapid Upper Limb Assessment (RULA) tool. RULA is an observation-based screening tool which has been widely used to assess the postural risk of IT device users. However, it has not yet been specifically utilized with smartphone users. The RULA tool scores identified ergonomics risks from using smartphones to text. Most smartphone users had a total RULA Grand Score of 6 for both sides (left side: 80.00%, right side: 90.00%), indicating the need for further investigation and changes (Action Level 3). Notably, no participants had acceptable RULA Grand Scores of 1 or 2. The correlation between musculoskeletal disorders and the ergonomic risk among smartphone users was determined using the Chi-Square test and Fisher's exact test; p<0.05 was considered statistically significant. There was a significant correlation between right RULA Grand Score and neck musculoskeletal disorder (χ2 = 9.424 at p value = 0.009) and right RULA Grand Score and upper back musculoskeletal disorder (χ2 = 31.717 at p value <0.001). RULA Score B (combination of neck, trunk and leg postures) and RULA Score D (combination of Score B, muscle use and force scores for group B) were also significantly correlated with neck musculoskeletal disorders (χ2 = 19.286 at p value<0.001 and χ2 = 9.310 at p value = 0.002 respectively). The RULA results identified the high ergonomics risk of smartphone users, this resulted from two key risk factors: posture and muscle use. The neck, trunk and leg postures had a combined effect on neck musculoskeletal disorders. Future investigations should consider these factors when designing ergonomic interventions for smartphone users.

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