Control room operators in a nuclear power plant participated in this on-site study to test the belief that keeping busy helps sustain alertness. Since circadian rhythms strongly affect alertness, the study was designed to account for different times of the 24-hour day.The participating reactor operators worked rotating 8-hour shifts in the control room. Every 20 minutes they reported their alertness and their workload during the preceding period. These ratings were obtained throughout three of each shift, for a total of nine shifts and 560 pairs of ratings. Reduced alertness ratings (2 and 3 on the 9-point alertness scale) occurred only during the early morning hours. For these hours, results indicated a significant positive relationship between alertness and workload, with lower alertness ratings tending to occur following 20 minutes of low workload.
Roger Jensen, R.C., (2015). Field study confirms the belief that keeping busy helps control room operators sustain alertness during the night shift. Procedia Manufacturing, 03, 1297-1304. doi:10.1016/j.promfg.2015.07.276