A STUDY OF ADAPTIVE REACTIONS OF THE CARDIORESPIRATORY SYSTEM IN PSYCHOEMOTIONAL STRESS CONDITIONS.

The article presents modern data on the physiological mechanisms study of the stress resistance development, which occurs in medical students in the dynamics of studying in higher educational institution in junior courses (1-3 courses). The adaptive reactions of the cardiorespiratory system in conditions of psychoemotional load were studied. Results showed that development of adaptation syndrome in those conditions greatly depends on speed of formation and intensity level of intersystem integration in cardiorespiratory system. That relation is revealed most of all on the background of physical activity (load on bicycle ergometer to the full). The variability of stages of adaptation development was found out. In first group of students the first stage of adaptive syndrome is characterized by activation of non-specific adaptive mechanisms (1st year of studies), that is naturally replaced by second stage - specific adaptive reactions, when the intellectual work capacity increases on the background of rationalization of its autonomic supply. In second group of students the second variant of adaptation development occurs - non-specific adaptive mechanisms (1st stage) on the 2nd year of study are changed by the stage of specific adaptation (2nd stage), that is accompanied by excessive psychophysiological indexes. On the 3rd year of study it leads to the depletion of adaptive capabilities (3rd stage). In third group of students the stage of activation of non-specific adaptive mechanisms was rapidly changed by their depletion, that was accompanied by decrease of intersystem integration and intellectual workability. Therefore, the formation of adaptive optimum occurs only in 40% of students. The majority (60%) of students-young women show either the initially insufficient adaptive capabilities, or excessive adaptation. Both insufficient and excessive adaptation naturally leads to psychological and autonomic disorders followed by appearance of psychosomatic neurotic manifestations. The prospects of future research from our point of view should lie in further investigation of gender peculiarities of adaptive reactions development up to psycho-emotional stress that develops in conditions of studying in university. That will make an opportunity to reveal the features of mechanisms of resistance formation depending on gender.

Ligament creep cannot be predicted from stress relaxation at low stress: a biomechanical study of the rabbit medial collateral ligament.

In normal daily activity, ligaments are probably subjected to repeated loading rather than to repeated deformation. The viscoelastic response to repeated loading is creep; this effect has significance for ligament reconstructions, which potentially "stretch out" over time. However, most experimental studies have examined the viscoelastic response to repeated deformation, stress relaxation. We hypothesized that the creep of a ligament could be predicted from its stress-relaxation behaviour. Left and right medial collateral ligaments of eight skeletally mature rabbits were subjected to either creep or stress-relaxation testing under comparable conditions. The time-dependent increase in strain (creep) and reduction in load (relaxation) from the tests were modelled with use of the quasilinear viscoelastic theory and generalized standard linear solid modelling. Ligaments were found to creep distinctly less than would be predicted from relaxation tests. Although the reason for this behaviour remains unknown, we speculate that it is due to the progressive recruitment of collagen fibres during creep.