Ogutu Jack, Park Woojin
Department of Applied Engineering, Safety & Technology, Millersville University, Millersville, PA, USA.
Department of Industrial Engineering, Seoul National University, Seoul, Korea.
Work. 2015;52(1):19-30. doi: 10.3233/WOR-141946.
Few studies have investigated mathematical characteristics of the discomfort-time relationship during prolonged static posture holding (SPH) on an individual basis. Consequently, the discomfort-time relationship is not clearly understood at individual trial level.
The objective of this study was to examine discomfort-time sequence data obtained from a large number of maximum-duration SPH trials to understand the perceived discomfort-posture holding time relationship at the individual SPH trial level.
Thirty subjects (15 male, 15 female) participated in this study as paid volunteers. The subjects performed maximum-duration SPH trials employing 12 different wholebody static postures. The hand-held load for all the task trials was a ``generic'' box weighing 2 kg. Three mathematical functions, that is, linear, logarithmic and power functions were examined as possible mathematical models for representing individual discomfort-time profiles of SPH trials.
Three different time increase patterns (negatively accelerated, linear and positively accelerated) were observed in the discomfort-time sequences data. The power function model with an additive constant term was found to adequately fit most (96.4%) of the observed discomfort-time sequences, and thus, was recommended as a general mathematical representation of the perceived discomfort-posture holding time relationship in SPH.
The new knowledge on the nature of the discomfort-time relationship in SPH and the power function representation found in this study will facilitate analyzing discomfort-time data of SPH and developing future posture analysis tools for work-related discomfort control.
很少有研究在个体层面上调查长时间保持静态姿势（SPH）期间不适与时间关系的数学特征。因此，在个体试验水平上，不适与时间的关系尚不清楚。
本研究的目的是检查从大量最大持续时间的SPH试验中获得的不适-时间序列数据，以了解个体SPH试验水平上感知到的不适与姿势保持时间的关系。
30名受试者（15名男性，15名女性）作为有偿志愿者参与了本研究。受试者采用12种不同的全身静态姿势进行了最大持续时间的SPH试验。所有任务试验的手持负荷是一个重2千克的“通用”盒子。研究了三种数学函数，即线性、对数和幂函数，作为表示SPH试验个体不适-时间曲线的可能数学模型。
在不适-时间序列数据中观察到三种不同的时间增加模式（负加速、线性和正加速）。发现带有附加常数项的幂函数模型能够充分拟合大多数（96.4%）观察到的不适-时间序列，因此，被推荐作为SPH中感知到的不适与姿势保持时间关系的一般数学表示。
本研究中发现的关于SPH中不适-时间关系性质的新知识以及幂函数表示，将有助于分析SPH的不适-时间数据，并开发未来用于控制与工作相关不适的姿势分析工具。
