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The aim of this study was to investigate fluctuations in heart rate variability (HRV), which reflect autonomic nervous system (ANS) function and potential psychological and physical strain, among 24 health care workers during work and sleep during four consecutive extended work shifts. Data included 24/36/12 h of HRV measurements, two logbooks, and a questionnaire. A cross-shift/cross-week design was applied. HRV was measured during work, leisure time, and sleep. The HRV data included time-domain [mean RR, SD of normal to normal R-R intervals (SDNN), and root mean square of the successive differences (RMSSD)] and frequency-domain [low frequency (LF)/high frequency (HF) ratio] parameters. HRV parameters revealed significant differences among work, leisure time, and sleep. Mean RR, RMSSD, and SDNN values were lower and the LF/HF ratio was higher on the first versus last day of the work period; however, the differences were most prominent in the morning hours. The results indicate higher levels of cardiovascular stress on the first versus fourth day of the working period, and measurements at night indicate a satisfactory recovery from the extended shifts.

The aim of this study was to analyze the activity of the trapezius muscle and the arm acceleration during the course of a workday in office employees. It was examined if there are significant changes in trapezius muscle activity in the afternoon compared to the morning work period and relationships to the level of arm acceleration during lunchtime. Nineteen female office employees were recruited. A one hour period of the work in the morning, afternoon, and lunchtime were compared. The measures of the trapezius muscle activity and muscle rest time (TR) did not significantly differ between working in the morning (TR: median 10%; range 1%-49) or working in the afternoon (TR: median 18%; range 2%-34%). The 90th percentile of arm acceleration during lunch time significantly correlated with less trapezius muscle activity in the afternoon compared to the morning values (RT: Spearman R=0.80; p

This study compared subjective sleep and subjective health complaints among Norwegian oil rig workers, before and after a two week work period. The study also compared differences between two different work schedules. The workers worked either two weeks of day shift (n=90) or two weeks of a swing shift schedule (n=93), involving one week of night shifts, immediately followed by one week of day shifts. Overall, the workers reported significantly poorer sleep quality and more complaints of insomnia at the end compared to the start of the work period. However, there was no significant difference in terms of subjective health complaints. Furthermore, there were no clear differences in changes in sleep quality, insomnia or subjective health complaints during the work period between day- and swing shift workers. However, at the end of the work period a higher proportion of insomniacs were seen among swing shift workers compared with day workers. To conclude, sleep quality and complaints of insomnia became worse during the work period. However, there were few differences in changes in terms of sleep or subjective health complaints between day- and swing shift, suggesting that 12 h day shift affected sleep and health similarly to the schedule involving night work.

The aim of this study was to investigate self-reported health effects of extended work hours (10 h on/14 h off) for 21 d at work/21 d off, for 40 male tunnel workers in an Arctic area. A questionnaire obtaining information about demographics and subjective health complaints (SHC), including musculoskeletal, pseudoneurological, gastrointestinal, allergic, and flu-like complaints the last thirty days was distributed on day 14 of a work period. In addition questions on coping, psychological job demands, control, and social support were asked. The questionnaire was repeated three times during a nine months observation period. Twenty-six workers completed all three questionnaires. The prevalence of subjective health complaints did not change during the observation period. The prevalence of subjective health complaints was the same or lower than in a control group. There was a slight increase in self-reported job demands during the observation period. Coping, job control, and social support from colleagues and management were reported high and did not change. No association between this type of long work hours and changes in self-reported health was found in this study. However, this might have been a selected group of workers, and the same results may not be found in another population.

The purpose of the present study was to examine how an inserted break influences the cardiovascular and central nervous system responses during periods of mental work. Twelve males conducted two 20-min periods of mental work with a 3-min break between them. Cardiovascular and central nervous system responses were measured continuously. In comparison to the baseline, cardiovascular responses increased continuously even after the inserted break, while, on the con- trary, central nervous system activity did not significantly increase during the work periods but relaxed during the break. The work performance increased during the second work period. These results suggest that the inserted break proposed by VDT guidelines in Japan was effective in relax- ing the central nervous system but was insufficient to prevent the increase in cardiovascular load. The results also imply that taking rests frequently is important not only to maintaining perfor- mance but also to preventing cumulative physiological workloads.