Sex-specific effects of sitting vs standing on upper body muscle activity during text typing

A systematic review of research on sitting and working furniture ergonomic from 2012 to 2022: Analysis of assessment approaches

This study analyses which aspects of sitting and working furniture ergonomics that may be influenced and how they are assessed. To gather information on the types and assessment techniques connected with influencing furniture ergonomics, a systematic review of the literature was conducted. The papers in the systematic review were published between 2012 and 2022. The articles applied the Systematic Reviews and Meta-Analyses (PRISMA) statement guidelines to limit the 41 papers that were eventually included (N = 41) to those containing keywords like ergonomics, human factors, comfort, working furniture, Chair, assessment and evaluation. The research objective of this systematic review is to provide a comprehensive overview of sitting and working furniture and the main findings, obtaining common assessment techniques for this type of furniture and their suitability. According to the relevant studies, the publications were categorized by summarizing factors like region, gender, research methods, ergonomic assessment techniques and methods used, correlation between assessment techniques and methods, etc. Summaries of the data extracted from the included papers are provided and the applicability of some approaches are assessed. Only a small number of authors have evaluated the ergonomics of furniture used in homes. One of the research gaps is the paucity of research on gender segregation, secular trends, and cultural contexts. These studies heavily rely on quantitative research techniques, and the articles may lack credibility due to the homogeneity of the evaluation techniques. Finally, the authors offer some suggestions for the appropriate ergonomic analysis of furniture.

Musculoskeletal disorders risk assessment methods: a scoping review from a sex perspective

The evidence points to differences in the impact of musculoskeletal disorders (MSD) in males and females due to different exposure to risk factors and inherent characteristics. To identify risks associated with MSDs, ergonomic assessment is carried out by applying various methods. The aim of this scoping review was to determine to what extent ergonomic assessment methods consider sex-related factors and if they were found to do so, to determine the extent of this consideration. A total of 31 papers on 32 ergonomic assessment methods were analysed in the review. Of these 32 methods, only 6 considered sex as an assessment parameter or when interpreting the results. The results revealed that the limited consideration given to the sex factor in ergonomic methods, together with the different impacts of MSDs and their consequences according to a person's sex, supports the importance of including sex factors in ergonomic assessment methods. Practitioner summary: This scoping review determined to what extent ergonomic assessment methods consider sex-related factors and if they do so, to establish the extent of such consideration. Of the 32 methods analysed, only 6 considered a person's sex. The results revealed that only a limited consideration is given to the sex factor in ergonomic methods.

Effect of sit-stand workstation position and computer task on head and trunk postural sway and discomfort

Adjustable-height desks may provide musculoskeletal health benefits to offset the effects of prolonged sitting. One mechanism may be increased postural variability, here characterized by head and trunk postural sway. Linear acceleration of the head and trunk were measured while participants used computer workstations in seated and standing positions during keyboard and mouse tasks; secondary measures were discomfort and proprioception (head and neck repositioning error). Median accelerations of the head and trunk were 20-26% lower in mouse tasks compared to keyboard tasks (p < 0.01). There were no significant differences in sway parameters between seated and standing positions. Discomfort and proprioception were correlated; subjects who experienced increased neck discomfort after 1.5 h of computer work had almost twice the head and neck repositioning error. The results suggest that postural sway is more affected by different tasks (keyboard vs. mouse) than by different workstation configurations and that low proprioception acuity may relate to the development of discomfort.

The Effect of Cycling While Typing on Patterns of Upper Body Muscle Activation

OBJECTIVE

To investigate the effect of one's sex and pedaling intensity on upper body muscle activation patterns during typing while cycling.

BACKGROUND

Females are at a higher risk for computer work-related musculoskeletal disorders, and mobile workstations have been suggested to induce healthier muscular patterns compared with sitting. However, the neuromuscular characteristics of performing computer work in a cycling workstation have not been investigated.

METHOD

Twenty-two participants (10 females) completed a 60-min computer typing task while pedaling on a cycle ergometer at two different intensities (25%, 4% heart rate reserve). Surface electromyography (EMG) was recorded from seven muscles of the upper body. Effects of time, sex, and intensity were assessed for muscle activation (RMS), activation variability (CV), and normalized mutual information (NMI) via generalized estimating equations.

RESULTS

With time, neck/shoulder CV increased in males during higher pedaling intensity, whereas in females it decreased during lower intensity. In females, RMS of neck/shoulder and NMI of neck/shoulder muscle pairs were lower, whereas forearm RMS was 34.2% higher with higher intensity cycling compared with lower intensity. Lower back RMS decreased 28.3% in the initial half of the task in females, but in males it increased 14.4% in the later half.

CONCLUSION AND APPLICATION

Cycling workstation showed a sex- and intensity-specific EMG response. These differing responses should be considered when implementing the use of cycling workstation and may be important for preventing/managing sex-specific muscle fatigue and musculoskeletal disorders.

Impact of a 10-min typing task in the development of trapezius myalgia: a preliminary observational study

Objectives. Computer use, as in typing, might contribute to trapezius myalgia (TM) development by increasing upper trapezius (UT) muscle fatigue. The purpose of this study is to investigate whether 10 min of performing a typing task by a population at risk would show significant changes in surface electromyography (sEMG) and pressure pain threshold (PPT) measurements. Supported and unsupported forearms postures are compared. Methods. Sixteen asymptomatic volunteers with minimum daily use of a computer of 5 h were randomized into two groups: fully supported forearms (n = 8) and unsupported forearms (n = 8). The protocol consisted of 10 min of a typing task, and the workstation was set according to the usual participant profile. sEMG and PPT readings were collected from both UT muscles. Results. PPT and sEMG readings were not significantly different among the two groups. Supported forearms had less reduction of PPT and a smaller increase in electrical activity. Conclusions. Ten minutes of typing seems insufficient to observe any significant changes that could lead to TM development.

The Speed of Optic Flow Stimuli Influences Body Sway

Optic flow is a perceptual cue processed for self-motion control. The aim of this study was to investigate whether postural control is modulated by the speed of radial optic flow stimuli. The experiments were performed on 20 healthy volunteers using stabilometry and surface electromyography (EMG). The subjects were instructed to fixate a central fixation point while radial optic flow stimuli were presented full field, in the foveal and in the peripheral visual field at different dots speed (8, 11, 14, 17 and 20°/s). Fixation in the dark was used as control stimulus. The EMG analysis showed that male and female subjects reacted to the stimuli with different muscle activity (main effects for gender, muscle and laterality: p < 0.001). The analysis of the center of pressure (COP) parameters showed that optic flow stimuli had a different effect on the left and right limbs of males and females (main effects of laterality: p < 0.015; interaction effects of gender and laterality: p < 0.016). The low speed of optic flow stimuli (8 and 11°/s) evoked non-uniform directions of oscillations especially in peripheral stimulation in all subjects, meaning that optic flow simulating slow self-motion stabilizes body sway.

The effect of walking and stationary work on the acute back pain, muscle activation, posture and postural control of older women

Back pain is associated with activity such as walking or assembly line work that involves upper-body movement. However, no single study has explored the effect of these tasks on back pain, spinal angles and balance in an older adult female population. This study investigated changes in back pain, postural sway, upper-, lower- and full-spine angle and EMG activation of trunk muscles following 30 minutes of walking and a modified quiet standing task. Fourteen older adult females (62 ± 11yrs) with low to moderate chronic back pain were recruited as participants. Findings demonstrated that following these activities, increased acute back pain and upper-spine flexion occur although acute back pain was not clinically significant; postural control and muscle activation remained unchanged. This suggests that walking and modified quiet standing can lead to subtle acute back pain in older females that could be due to an increased upper spinal flexion rather than muscle fatigue. Practitioner summary: Back pain and postural problems are common in older adults. Older adult female participants experienced increased back pain and greater upper-spine flexion following 30-minute walking and standing with trunk rotation, but the practical importance was less clear. However, balance was unaffected, suggesting no increase in fall risk. Abbreviations: CBP: chronic back pain; MQS: modified quiet standing; QS: quiet standing; RPE: rating of perceived exertion; TD: trapezius descendens; TT: trapezius transversalis; TA: trapezius ascendens; ESL: erector spinae longissimus; C7: seventh cervical vertebrae; T7: seventh thoracic vertebrae; T10: tenth thoracic vertebrae; T12: twelfth thoracic vertebrae; L2: second lumbar vertebrae; S2: second sacral vertebrae; AP: anterior-posterior; ML: medial-lateral; SWAYtot: total postural sway; M: mean.

Ergonomic Design of Manual Assembly Workstation Using Digital Human Modeling

Background

Manual assembly workers are exposed to risk factors of musculoskeletal disorders. The most important risk factor among the workers is static and awkward posture. This study aimed to the ergonomic design of manual assembly workstation using Digital Human Modeling (DHM).

Methods

This cross-sectional study was conducted among manual assembly workers. Data was gathered via 1) demographic/occupational questionnaire, 2) The Persian version of the Nordic General Questionnaire (P-NMQ), 3) Rapid Upper Limb Assessment (RULA) using Kinect sensor, 4) Hierarchical Task Analysis (HTA), 5) Idea Rating Sheet (IRS), 6) Anthropometric data of the participants, 7) CATIA software and RULA technique.

Results

The results of the evaluations showed that in the design of most workstations of assemblers in Shiraz electronics industries, complete ergonomic principles were not observed, and the implementation of targeted ergonomic interventions in them is necessary.

Conclusion

The prevalence of musculoskeletal symptoms is high among manual assembly workers. The RULA technique showed that the designed manual assembly workstation using DHM effectively could improve the subjects' awkward postures.

Shear-wave elastography for assessment of trapezius muscle stiffness: Reliability and association with low-level muscle activity

Purpose

Shear-wave elastography has been recognized a useful tool for quantifying muscle stiffness, commonly reported as shear modulus, however the reports on reliability are often limited to test-retest correlations. In this study, we explored the reliability of shear-wave elastography for assessment of the trapezius muscle stiffness and its relationship with low-level muscle activity.

Methods

Twenty participants were included in a two-session experiment. Measurements of shear modulus and muscle activity were performed at rest and during low-level activity, induced by shoulder abduction without additional external resistance.

Results

Good to excellent intra-session repeatability (ICC > 0.80) and moderate inter-rater and inter-session reproducibility (ICC = 0.66–0.74) were observed. Typical errors were acceptable (7.6% of the mean value) only for intra-session measurements in resting conditions, but not acceptable for all conditions with low-level muscle activity (10.2–16.6% of the mean value). Inverse relationships between shear modulus and muscle activity at 40° and 60° of shoulder abduction (r = -0.53 and -0.57) were observed on a group level. We also found higher shear modulus in males compared to females, for the parallel probe position compared to the perpendicular position (in relation to muscle fiber orientation), and for the dominant side of the body compared to the non-dominant side.

Conclusions

This study showed an inverse relationship between muscle activity in low-level range and shear modulus on a group level, suggesting inherent passive stiffness could account for a larger portion of the variance (compared to muscle activity) in shear modulus when the muscle activity is low. Our results imply that shear-wave elastography can be used in research exploring muscle stiffness, however, caution is needed since only intra-session examination in resting conditions showed acceptable within-participant typical errors. The secondary analyses of the study showed higher shear modulus for males, for the non-dominant side of the body and for the parallel orientation of the ultrasound probe.

Considering sex and gender in ergonomics: Exploring the hows and whys

At the 2018 IEA conference, the Gender and Work Technical Committee organized three symposia with over 20 presentations. Overall, these contributions positioned ergonomics as a theoretical and pragmatic approach developing innovative methods to integrate sex/gender analysis into the construction and evaluation of interventions. This special issue of Applied Ergonomics includes diverse approaches to the consideration of sex and gender in ergonomics, including methods in accident analysis, musculoskeletal disorders, work-family interactions, work schedule analysis, prevention programs and evaluation of interventions. The contents are summarized in this introduction.