Physical training intervention in female shift workers: II. The effects of intervention on the circadian rhythms of alertness, short-term memory, and body temperature

Abstract

The effects of a physical training intervention on the circadian rhythms of alertness, short-term memory performance (SAM-test) and oral temperature (t ₀) were studied in 75 nurses and nursing aides working irregular shifts in a hospital. Measurements were made every two hours during the days of one morning and two night shifts. In the training group (T), fatigue decreased significantly during the night but not during the day compared to the control group (C). No significant changes were found in the circadian rhythms of the SAM-test and t ₀ between the groups, but inside the T group, performance in the SAM-test improved significantly during the day and night shifts, and the mesor and amplitude of t ₀ decreased during the day of a morning shift. The results suggest that physical training can induce changes in the circadian rhythms of shift workers which may be interpreted as an adaptation to shift work.