Effects of Physical Workload on Salivary Cortisol Level / 대한산업의학회지

OBJECTIVE: Workload is known to affect the hypothalamus-pituitary-adrenal axis. Although many studies had revealed that job stress related factors could affect the neuroendocrine system among blue-collar workers, these studies had limitations as they had not evaluated the workload by objective methods which took into consideration individual physiological differences. This study was conducted to evaluate the effects of physical workload adjusted job stress on cortisol regulation by using objective tools for workers having various job tasks. METHODS: Among 110 foundry workers, shipyard workers, and fine machine assemblers for whom saliva samples were obtained, 102 without any past history of conditions that could affect hormonal regulation such as diabetes, and hypertension were included in this study. Among the 102 study participants, 15 workers whose saliva for morning or afternoon or heart rate monitoring data was not attained were excluded from the final analysis. Workload was evaluated by RHR (relative heart rate) using a heart rate monitor, and job stress was evaluated by Karasek's Job Content Questionnaire. Saliva samples were gathered during 8 - 9 am and 5 - 6 pm, and salivary cortisol levels were analysed by radioimmunoassay. RESULTS: After adjusting several variables which could effect cortisol secretion including job stress, among the higher RHR group morning salivary cortisol level was increased (beta=60.32, S.E.=26.35, p=0.0266), afternoon salivary cortisol level was decreased (beta=-7.43, S.E.=29.73, p=0.8044), and salivary cortisol level difference between morning and afternoon was increased (beta=72.10, SE=35.50, p=0.0509). CONCLUSIONS: As physical workload increases morning cortisol level, which is caused by the effect of arousal, and decreases afternoon cortisol level, which is caused by exhaustion, physical workload enlarges the width of diurnal cortisol variance. Therefore, physical exhaustion due to excessive workload could have adverse effects on the neuroendocrine system.

Reliability and Validity of Questionnaire for Assessing Physical Workloads / 대한산업의학회지

OBJECTIVES: The aims of the study were to make a questionnaire for assessing physical workloads and to evaluate its reliability and validity. METHODS: A total of 220 workers (foundry workers 30, large vehicle assemblers 30, shipyard workers 75, and automobile manufacturers 80) completed a self-administered questionnaire and took examinations for physical work capacity and working heart rate. We excluded data with insufficient responses or incorrect physical work capacity and working heart rate. Finally, the data of 154 workers (70.0%) were used for our study. In order to evaluate the reliability and validity of the questionnaire, we used statistical analyses including the scaling assumption test and a comparison with the objective tool for physical workload which was evaluated by working energy expenditure. RESULTS: The items of the questionnaire in the same categories had close distribution in the evaluation of the scaling assumption. The item internal consistency was 0.41-0.73 for posture factor, and 0.62-0.79 for non-posture factor. The item discriminate validity was 100%. Cronbach's alphacoefficient of the total items was 0.73 (0.58 for posture factor and 0.74 for nonposture factor). In the correlation between working energy expenditure and questions, general physical activity (p=0.008), proportion of the workday with hands above shoulder (p=0.002), proportion of the workday with trunk bent (p=0.028), proportion of the workday with awkward posture (p=0.048), sweating after work (p=0.006), total scales (p=0.003) and Borg scale (p=0.011) all had statistical significance. CONCLUSIONS: Our questionnaire for assessing physical workloads demonstrated statistically significant reliability and validity. But the questions for the proportions of the workday with sitting work posture and with static posture should be modified via a larger study.