Within the limits of researches of medical and biologic problems of work on a rotational basis in regions with extreme climatic conditions, the concept of suboptimal strategy of adaptation as "incomplete adaptation" (IA) has been developed. A basic IA at work on a rotational basis makes synchronisation infringement of functions which develops at a change of time zones at cross-meridian migrations, and as a result of occurrence of climatic stress at cross-latitude migrations. The condition of IA is characterised by reactive anxiety, inversion of inter-hemisphere domination, infringement of circadian rhythms, boundary shifts of the hormonal status, the lowered physical and intellectual working capacity, features of psycho-somatic tiredness. In modelling experiments, it is shown that chronic infringement of circadian rhythms at IA has the expressed "acute" form which then later passes into the hidden form. In the phase of hidden form, functional reserves of the organism decrease and the risk of diseases increases.