Effects of backrest density on lumbar load and comfort during seated work / 中华医学杂志(英文版)

<p><b>BACKGROUND</b>Seated workplaces have greatly increased in China. Many researchers have found that seated work is a risk factor in the development of low-back pain. Backrest can reduce the load on the lower back by transmitting more of the weight from the upper body to the floor via the backrest so as to prevent low-back pain. To design a suitable chair backrest for seated office work, some backrest parameters must be optimized. In this study, the role of backrest density on lumbar load and comfort were investigated. The goal of the study was to help establish criteria with which backrests that alleviate and prevent low back pain during seated office work can be designed and selected.</p><p><b>METHODS</b>Twenty volunteers (10 men and 10 women) were seated in three backrest conditions (10 kg/m(3), 25 kg/m(3), and 40 kg/m(3)). Pressure data, including contact pressure (CP), peak contact pressure (PCP) and contact area were collected during 15-minute trial. Subjective data were collected after each pressure test.</p><p><b>RESULTS</b>Backrest density had a significant effect on backrest pressure variables. CP and PCP increased with increasing backrest density. Contact area decreased with increased density. In terms of user preference, the backrest with low density was most highly rated.</p><p><b>CONCLUSIONS</b>Backrest density plays an important role in lumbar load and comfort during seated work. During designing and selecting backrests, backrest density should be focused on so as to alleviate and prevent low-back pain during seated office work. Backrest density at 10 kg/m(3) got the lowest CP and PCP and largest contact area. Backrest with low density can reduce lumbar pressure and increase support contact area, which could raise comfort feeling. Backrest density at 10 kg/m(3) is better to maintain a balance between providing effective support and alleviating excess lordosis.</p>

Study on effect of backrest thickness to lumbar muscle fatigue during computer work / 中华劳动卫生职业病杂志

<p><b>OBJECTIVE</b>To investigate the relationship between backrest thickness and lumbar muscle fatigue so as to confirm the fitting backrest thickness.</p><p><b>METHOD</b>Twenty subjects coming from university seated at a computer workstation in three backrest thicknesses: 4, 7 and 10 cm. The time that the subjects reported the lumbar muscle fatigue was collected during each trial and subjective appraise was collected at the end of the entire protocol.</p><p><b>RESULTS</b>The MF value decreased and lumbar muscle felt fatigue in all three backrest thickness. Subject could feel fatigue more late [(45.0 +/- 10.8) min] and subject felt more comfort at 7 cm thickness.</p><p><b>CONCLUSION</b>It is better to relive computer worker lumbar muscle fatigue when the backrest thickness was kept on 7 cm. Work break was needed because one hour work could cause muscle fatigue.</p>

Risk factors of low back pain among the Chinese occupational population: a case-control study / 生物医学与环境科学（英文）

<p><b>OBJECTIVE</b>To explore the risk factors of low back pain among the Chinese occupational population in several major industries.</p><p><b>METHODS</b>A total of 7200 subjects (3600 cases and 3600 controls) were randomly sampled from a cross-sectional study, and they were investigated for individual and occupational factors of low back pain. The potential risk factors were first selected by using chi-square tests. Secondly, collinearity diagnosis proceeded by using the Kendall's rank correlation. Finally, binary logistic regression model was used for multi-factor analysis.</p><p><b>RESULTS</b>Collinearity diagnosis showed that there was a severe collinearity problem among the potential risk factors of low back pain. Logistic regression model included 20 variables with statistical significance. Bending neck forward or holding neck in a forward posture for long periods (OR=1.408) was the most important risk factor inducing low back pain in this study, followed by bending heavily with the trunk (OR=1.402), carrying out identical work almost for the whole day (OR=1.340). Additionally, sufficient normal break was a protective factor of low back pain.</p><p><b>CONCLUSION</b>Low back pain among the Chinese occupational population was associated with body height, occupation, work organization, physical work, working posture, and others. All these risk factors could be regarded as the indicators of low back pain, and some relevant preventive measures should be taken to reduce low back pain risk.</p>