Postural and Muscular Responses While Viewing Different Heights of Screen

Effects of laptop screen height on neck and shoulder muscle fatigue and spine loading for office workers

BACKGROUND

Due to the unfavourable neck-shoulder muscle loads caused by poor posture, the people who use the laptop for a long time may face the risk of neck and shoulder injuries.

OBJECTIVE

The purpose of this study investigates the impact of the screen height on the muscle activation of head flexion, neck and shoulder, and the cervical spine torque to provide the favorite screen height for laptop user.

METHODS

Twelve healthy young participants completed a15-minute task of the reading at the four different screen heights. sEMG signals of the splenius capitis (SC) and upper trapezius (UT) were measured and calculated the root mean square (RMS) and mean power frequency (MPF) to determine muscle fatigue. The different height of laptop users was simulated and the forces on the spine of users at different screen heights were analyzed by Jack.

RESULTS

Adjusting the height of the laptop screen can effectively reduce head flexion and muscle activity of SC and UT, and has a positive effect on reducing fatigue of SC, but has no significant effect on UT.

CONCLUSIONS

Adjusting the height of the laptop screen can delay the occurrence of SC muscle fatigue to a certain extent. The joint analysis of sEMG spectrum and amplitude reports that the screen heights of D15 and D45 have the highest and the lowest frequency of fatigue, respectively. At the same time, the moment of spineT1/T2 and spineL4/L5 decrease with the increase of screen height.

Ergonomic evaluation of the risk factors causing pain in the upper part of the body among IT professionals in India

BACKGROUND: In developing countries, the recent increase in computer-related work has considerably increased the occupational complaint of pain. OBJECTIVE: To examine the effects of workstation design, posture and ergonomic awareness on the prevalence of pain for a year in the upper part of the body (eyes, hands, arms, shoulders, lower back, and upper back) among IT professionals in India. METHOD: To investigate the association of risk factors with the prevalence of pain in different body parts, a newly designed online questionnaire titled “A Questionnaire based on ergonomics for IT Professionals” was developed. The psychometric properties of this questionnaire were tested. 110 computer office workers were recruited from IT companies from major cities in India. RESULTS: The confirmation of reliability and lack of redundancy of items was provided by the calculation of internal consistency (Cronbach’s alpha 0.804) and cross-validation. 60% of participants was male. Mean age was 29.73±6.09 years. The prevalence of pain for a year in the upper part of the body was 38.2%. The frequently reported pains were in the neck (22.7%), lower back area (22.7%), and eye strain (21.8%). CONCLUSION: It was identified that long working hours, excessive usage of smartphones, lack of exercise, incorrect workstation adjustments, and incorrect posture were the risk factors for the prevalence of pain.

Using evidence to support the design of submarine control console workstations

PURPOSE

This paper outlines an approach to develop practical guidelines to support the design of submarine control console workstations.

METHOD

Guideline development was undertaken for 13 physical design criteria, provided to the research team. Data was gathered from four sources: a systematic literature review, relevant standards, population specific anthropometric data, and user focus groups. The systematic review included risk of bias, quality assessment and evidence synthesis.

RESULTS & CONCLUSION

The systematic review retrieved 43 relevant articles in relation to seven of the 13 design criteria. Very few high-quality studies were identified. The combined evidence available from each of the four data sources was collated and used to provide a set of guidelines for each of the 13 criteria, highlighting the importance of the use of multiple data sources. This approach has applicability beyond this study where the need exists to collate evidence sources beyond the scientific literature.

Effects of Cervical Flexion on the Flexion-relaxation Ratio during Smartphone Use

[Purpose] The purpose of this study was to measure the cervical flexion-relaxation ratio (FRR) and intensity of neck pain and identify the differences according to postures adopted while using smartphones. [Subjects] Fifteen healthy adults with no neck pain, spinal trauma, or history cervical surgery participated in this study. [Methods] The activity of the cervical erector spinae muscle was recorded while performing a standardized cervical flexion-extension movement in three phases (flexion, sustained full flexion, extension). And neck pain intensity was recorded using a visual analog scale (VAS) with values between 0 and 10. Postures held while using a smartphone are distinguished between desk postures and lap postures. The FRR was calculated by dividing the maximal muscle activation during the extension phase by average activation during the complete flexion phase. [Results] No significant differences were found in the FRR between desk posture, lap posture, and baseline, though the intensity of the neck pain increased in the lap posture. [Conclusion] The FRR could be a significant criterion of neuromuscular impairment in chronic neck pain or lumbar pain patients, but it is impossible to distinguish neck pain that is caused by performing task for a short time. Prolonged lap posture might cause neck pain, so the use of smartphones for a long time in this posture should be avoided.