AFTER-EFFECTS OF NIGHT WORK ON PHYSICAL PERFORMANCE CAPACITY AND SLEEP QUALITY IN RELATION TO AGE

The after-effects of night work on physical performance capacity and s leep quality were studied. Ten younger (age less-than-or-equal-to 34 y ears) and eight older (age > 34 years) experienced shift workers were examined. Subjects performed cycle ergometer tests at an exercise inte nsity requiring 70% of the individual maximal oxygen uptake. Two condi tions were studied: a baseline condition, i.e. the last day of a 4 day s-off period, and a recovery condition after a period of seven consecu tive night shifts, i.e. the second day-off after the night-shift perio d (32 h after leaving the night-shift period). Sleep quality of the sl eep period preceding the test was also measured for both conditions. D uring the recovery condition the endurance time (i.e. time to exhausti on) was reduced by an average of 20% (-160 s, P < 0.05) for the older shift workers only. In both age groups exercise ventilation, heart rat e, oxygen uptake, perceived exertion and sleep quality remained unaffe cted. These findings support the hypothesis that the aging shift worke r is faced with increasing complaints, even after the night-shift peri od. However, to clarify the mechanisms responsible for these after-eff ects of night work, further extensive studies must be designed.