Workload variations and its reflection in parameters of cognitive performance and cardiovascular system functioning in electricity distribution network controllers

Introduction
Expressed uneven workloads and unpredictability of their sharp increase under extreme situations are the characteristics of electricity distribution network controllers’ work. The aim was to reveal the variations in the workload of controllers and its reflection in parameters of cognitive performance and CVS functioning at the different working shifts.

Methods
Heart rate (HR), systolic (BPS) and diastolic blood pressure (BPD), perceived workload, fatigue, stress, tension using a 5-anchor scale were registered in 19 controllers after the 12-h shifts under their 2-day rotation during 5 months (N=913 subject-shifts). Short-term memory and attention switching were tested during a month (N=218 subject-shifts).

Results
Tension, fatigue and stress increased with an increase in a workload (p<0.000001); after the day shifts – also bloodcirculation intensified (Pillai’s test V=1.81, p<0.002); after the night shifts – the attention switching accelerated (p<0.05) reflecting its circadian rhythm. Workload depended on a shift-kind within 8-day cycle of their rotation (F=8.81, p<0.00007), at the second day shifts perceived higher than at the first ones (p<0.04); tension, fatigue and stress depended on a shift-kind (V=3.65, p<0.000001), but did not differ at the first and second shifts. At the day shifts the workload, tension, fatigue depended on a weekday (F=6.94;8.36;10.67, p<0.0001) decreasing on Saturday-Sunday; BPD, BPS/HR depended at p<0.05. After the easiest night shifts the short-term memory was the best, after the most loaded shifts – the worst one (p<0.05).

Discussion
The increase in workload is accompanied by increase in tension, fatigue, stress; at the day shifts - also by bloodcirculatory intensity and shows little effect on cognitive performance that meets the professional demand of the reliable human-operator work. Complications of cognitive performance are more pronounced after the night shifts. Evaluations of tension, fatigue and stress are less subjective compared to evaluation of workload and therefore are preferable for monitoring of controllers’ body state.