BACKGROUND: 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.
OBJECTIVE: 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.
METHOD: 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.
RESULTS: 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.
CONCLUSION: 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.
