Circadian variations in alertness, readiness for work and work efficiency

U organizmu čovjeka odvijaju se ritmički procesi različitih frekvencija odnosno perioda. Među njima za funkcionalno stanje čovjeka najvažniju ulogu imaju ritmovi čiji je period oko 24 sata (tzv. cirkadijurni ritmovi). Oni su utvrđeni na svim funkcionalnim razinama: od supcelularnog i staničnog nivoa preko organa i organskih sistema pa do organizma kao cjeline. U svakodnevnim prilikama ove su cikličke promjene u organizmu pod utjecajem ritmičkih promjena u okolini. Vanjski ritmički utjecaji potpomažu da se ritmičke promjene u organizmu bolje sinkroniziraju i da se organizam kao cjelina bolje prilagodi na svoju sredinu. Kod noćnog rada dolazi do inverzije ritma budnost/spavanje u toku dana; radnik mora raditi u ono vrijeme tijekom 24 sata kad je organizam u stanju deaktivacije, a spavati u ono vrijeme kad je obično budan i aktivan. Ove promjene u aktivnosti čovjeka predstavljaju dodatno opterećenje na koje se radnik mora prilagoditi da bi mogao dulje vrijeme raditi u smjenama. Tolerancija prema smjenskom (noćnom) radu povezana je s nekim karakteristikama radnika. Mjerenje tih karakteristika može poslužiti u utvrđivanju interindividualnih razlika u toleranciji prema smjenskom radu.Among various rhythmic processes with different frequencies (periods), which are present in the human organism, for normal functioning the most important are the rhythms with a cycle length of about 24 hours (termed circadian rhythms). Circadian rhythms have been confirmed at all levels of physiological functions: from subcellular and cellular mechanisms, to the organic systems and organism on the whole. In normal everyday circumstances the rhythmic processes in the human organism are synchronised with the rhythmic processes in the environment. The external rhythmic variations support internal synchronisation between various rhythms, and in that way make it possible for the organism to better adapt to the environment. The sleep-wake rhythm is inverted during night work: the worker has co work in the period of low activity level, and sleep during the day, when he is usually active and alert. In order to work in shifts the worker has to adapt to such disruptions of the sleep-wake pattern. Tolerance to shift work was found to be associated with some features of the worker. The measurement of such features could serve as determinate of interindividual differences in shift work tolerance level