Performance and alertness on 8 h and 12 h rotating shifts at a natural gas utility

Ergonomics. 1993 Oct;36(10):1177-93. doi: 10.1080/00140139308967987.


An 8 h/5-7 day shift schedule was compared with a newly instituted 12 h/2-4 day schedule in this, our second worksite study of extended workshifts. Workers completed a performance/alertness test battery, and a questionnaire on sleep patterns and other personal habits, 2-4 times a week on all shifts. After 10 months adaptation to the 12 h shift schedule, there were decrements in performance/alertness attributable to the extra 4 h on the extended shift. There were also reductions in sleep across the workweek which were most apparent on 12 h night shifts. The results are consistent with our first worksite study of 12 h shifts and indicate extra caution should be exercised when scheduling critical activities for extended workshifts, especially extended night shifts.

MeSH terms

  • Adult
  • Arousal*
  • Attention*
  • Circadian Rhythm*
  • Employee Performance Appraisal
  • Fossil Fuels*
  • Humans
  • Male
  • Middle Aged
  • Reaction Time
  • Work Schedule Tolerance*


  • Fossil Fuels