PubMed · 15035139
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Mika Yamauchi, Takeshi Sugishita, Toshitsugu Sugimoto. 2004. [pQCT].. https://pubmed.ncbi.nlm.nih.gov/15035139/
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Low back pain (LBP) has been identified as one of the most costly disorders among the worldwide working population. Sitting has been associated with risk of developing LBP. The purpose of this literature review is to assemble and describe evidence of research on the association between sitting and the presence of LBP. The systematic literature review was restricted to those occupations that require sitting for more than half of working time and where workers have physical co-exposure factors such as whole body vibration (WBV) and/or awkward postures. Twenty-five studies were carefully selected and critically reviewed, and a model was developed to describe the relationships between these factors. Sitting alone was not associated with the risk of developing LBP. However, when the co-exposure factors of WBV and awkward postures were added to the analysis, the risk of LBP increased fourfold. The occupational group that showed the strongest association with LBP was Helicopter Pilots (OR=9.0, 90% CI 4.9-16.4). For all studied occupations, the odds ratio (OR) increased when WBV and/or awkward postures were analyzed as co-exposure factors. WBV while sitting was also independently associated with non-specific LBP and sciatica. Vibration dose, as well as vibration magnitude and duration of exposure, were associated with LBP in all occupations. Exposure duration was associated with LBP to a greater extent than vibration magnitude. However, for the presence of sciatica, this difference was not found. Awkward posture was also independently associated with the presence of LBP and/or sciatica. The risk effect of prolonged sitting increased significantly when the factors of WBV and awkward postures were combined. Sitting by itself does not increase the risk of LBP. However, sitting for more than half a workday, in combination with WBV and/or awkward postures, does increase the likelihood of having LBP and/or sciatica, and it is the combination of those risk factors, which leads to the greatest increase in LBP.
The paper describes a procedure for estimating the material parameters of biological soft tissue by fitting model prediction to experimental load-deformation data. This procedure minimizes the error between data and theoretical model prediction through systematically adjusting the parameters in the latter. The procedure uses commercially available software and is not specific to any particular model; nevertheless, for illustration purposes, we employ a six parameter fibril-reinforced poroelastic cartilage model. We are able to estimate any and all of these parameters by the procedure. Convergence of the parameters and convergence of the arbitrary initial stress relaxation to the data was demonstrated in all cases. Though we illustrate the optimization procedure here for unconfined compression only, it can be adapted easily to other experimental configurations such as confined compression, indentation and tensile test. Furthermore, the procedure can be applied in other areas of biomechanics where material parameters need to be extracted from experimental data.
PURPOSE: Different criteria are used to define the terms mid-stance (MST) and mid-swing (MSW) when describing the gait cycle. None of these definitions is universally accepted. This causes difficulties with the interpretation of gait analysis data and hinders the comparison between the different studies. The aim of the present study was to compare three definitions of MST and MSW by examining the gait of a group of healthy children. METHOD: A prospective comparison of three commonly used definitions of the MST and MSW events of the gait cycle. OUTCOME MEASURES: The timing of the temporal, kinematic and kinetic MST and MSW of the gait cycle. RESULTS: Thirty healthy 8 - 10-year-old children were studied. There was no consistent correlation between the timing of the chosen definitions of MST and MSW. However, there was a tendency for the timing of the temporal and kinetic MST and MSW to occur, respectively, at approximately 30 and 80% of the gait cycle. CONCLUSIONS: The temporal definition of MST and MSW as the midpoints in time of the respective phases of the gait cycle appears to be more appropriate than other definitions. The use of this definition may prevent misunderstanding and permit comparison of the results of the different gait analysis studies.