Direct measurements of upper arm elevation among female hairdressers with special reference to exposure variability

摘要

The aim of the present study was to describe upper arm postures and movements among female hairdressers, with special emphasis on the variability between hairdressers, between days within hairdresser, and between tasks included in hairdressing. In total, 28 female hairdressers from 13 salons participated in the study. Data on upper arm postures relative to the line of gravity were collected for 4 consecutive working days using inclinometers attached to both upper arms. In order to discriminate work with customers from other tasks, the hairdressers noted customer on and off times in a diary. Customer work (CW) was defined as washing, cutting, colouring, styling and serving customers. Other tasks, i.e. auxiliary work (AW) included sweeping the floor, washing towels, unpacking deliveries, and breaks. For a number of posture variables, mean values and variance components within and between subjects were estimated for the whole work and for CW and AW separately in one-way random effect models using restricted maximum likelihood (REML) algorithms. Exposure variability was expressed in terms of the standard deviation (SD=square root of the variance) between subjects (SDBS) and between days (SDBD). The median posture for the right arm was on average 22.0° (SDBS=3.6° and SDBD=3.4°) during the full workday, during CW it was 23.3° (SDBS=4.6° and SDBD=3.9°), and during AW 21.0° (SDBS=3.6° and SDBD=3.9°). The hairdressers worked with the right arm elevated more than 60° 6.5% (SDBS=2.8% and SDBD=2.0%) of the time. Divided per task it was 9.0% of the CW-time (SDBS=4.8% and SDBD=3.4%), and 3.7% of the AW-time (SDBS=1.7% and SDBD=2.4%). Thus, posture variability between days within hairdressers was in the same order of magnitude as that between hairdressers. This suggests that “typical” work days do not exist. Precise exposure estimation for an individual hairdresser requires measurements during more than one day. The variable “time with arms above 60°” showed good contrast between customer work and auxiliary work, and may thus be a candidate for task-based modelling of job exposure.