From Big Medical Encyclopedia

HYPODYNAMIA (hypodynamia; grech, hypo-+ dynamis force) — reduction of the muscular efforts spent for deduction of a pose, movement of a body in space and also to physical activity. As G.'s reasons can serve physical., fiziol, and social factors (decrease in weight load of a musculoskeletal system, an immobilization, stay in the closed rooms of small volume, a slow-moving way of life, etc.). In the conditions of hypogravitation (subgravitation) or zero gravity it is connected with relative reduction physical. efforts and a metabolic cost on active overcoming body weight and the moved objects.

Upon transition of the person from vertical position in horizontal the vector of gravity becomes perpendicular rather longitudinal axis of a body. Weight loading is distributed on rather big bearing area. It leads to reduction of local tension and deformations, decrease in the general muscular activity and a metabolic rate. Similar, though not identical, the state is observed at immersion of the person in water when vectors of the pushing-out force and gravity are opposite directed and at equality of specific weight of a body and liquid there is a «weighed» state excluding need of overcoming gravity due to muscular efforts. Therefore water immersion and a long bed rest reproduce the typical situation characteristic of G., and they can also be considered as approximate model of zero gravity.

Prevalence of a hypodynamia increases in modern conditions in connection with processes of an urbanization, broad implementation in daily activity of the person of vehicles, automation and mechanization of work. Reduction of a share of manual nonmechanized skills is followed by relative increase in number of the professions connected with performance of operator functions (control of mechanisms, control) and also shares of brainwork in life of modern society. Improvement of living conditions, increase of a role of modern means of communication (phone, radio, television) objectively promote distribution of more passive forms of carrying out leisure as social and intellectual needs of the population are more and more stoutly satisfied in the conditions of rather less mobile way of life. In this regard the problem G. develops into a problem social, the successful decision a cut depends on joint efforts of physicians (clinical physicians, physiologists, hygienists, etc.), psychologists, sociologists, and also representatives of the public and sports organizations.

In literature the term «hypodynamia» is often applied as a synonym of a tipokineziya (e.g., to the description of conditions of an immobilization, a bed rest, stay in the closed rooms of small volume). However value of these terms not always matches since the hypokinesia means the restriction of space characteristics of the movement which is not necessarily connected with reduction of muscular efforts. So, during the flights at big space space stations G.'s condition is not followed by a hypokinesia since there freedom of movements and full volume of movements remains. Expediency of differentiation of concepts G. and hypokinesias (see) is caused also by distinction of forms of manifestation of responses of an organism. Effects of a hypokinesia are shown preferential in development of such structural changes and functional reorganizations as a tutopodvizhnost of joints, disturbance of a motive stereotype, coordination of movements, etc. Reduction of muscular efforts at G. leads to development in an organism functional and morfol, changes which represent a kind of adaptation shifts (adaptation to reduced loadings) and are expressed preferential in the phenomena of a detrenirovannost and «an atrophy from inaction». It is possible to carry the following to the most specific of them: reduction of power exchange and food requirement, development of a detrenirovannost of cardiovascular system, in particular myocardium; dystrophy of muscular tissue; negative nitrogenous balance; reorganization of a lipometabolism with a tendency to increase in a share of a fatty component in body weight; atherosclerotic processes and demineralization of a bone tissue. As a result of all this the general reactivity of an organism changes, its resistance to infections decreases, astenisation develops, physical falls. working capacity and resistance to stressful influences (e.g., to overloads), decreases orthostatic stability, etc. As the active motive mode is among the important factors defining longevity it is assumed that G. accelerates process fiziol, aging. In the most acute form of an effect of G. are shown in the conditions of extreme influences, and also in the course of a readaptation of an organism to usual conditions after long restriction of a physical activity. Depending on specific conditions of emergence it can be combined with change of intravascular pressure of blood, with shifts in activity of afferent systems, and also with a hypokinesia. In particular, in the conditions of zero gravity, a bed rest and water immersion of G. is followed by reduction of intravascular pressure in a lower body. The krovenapolneniye of upper parts of a body relatively increases in these cases that eventually via the corresponding neurohumoral mechanism leads to disturbances of a water salt metabolism, decrease in volume of the circulating blood, development of dehydration of an organism (Henry's reflex — Gower). Connect development with change of hydrostatic pressure of blood nevrol, the symptomatology depending on disturbance of cerebral circulation and also disturbance of tonic properties of walls of veins of the lower extremities (contractility and distensibility).

Medical and preventive actions at G. are various. Major importance among them belongs to physical trainings. Character of a training changes - depending on specific conditions of emergence of G. (a gigabyte. charging, production gymnastics, recreational and to lay down. physical culture etc.). In G.'s prevention also the events held in nation-wide scale figure prominently (sport, tourism, promotion of mass participation in delivery of standards of the GTO complex, scientific and educational work, etc.). Compensation of deficit of weight loading in state of weightlessness is reached by exercises on special exercise machines (see), and also use of suits for constant carrying with the rubber shock-absorbers creating a static load in the direction of a longitudinal axis of a body. As auxiliary ways of prevention can serve: electrostimulation of muscles, use of hormonal drugs from group of anabolic steroids, and also addition in a diet of potassium, calcium, phosphates and vitamins which losses at G. increase. For cases when G. is combined with decrease in hydrostatic pressure of blood, various ways of a special training directed to normalization of activity of cardiovascular system and a water salt metabolism are recommended (vacuum chambers for the lower half of a body, occlusal cuffs for extremities, breath under excessive pressure, rotation on the centrifuge of small radius, etc.). Recovery of reduced volume of blood can be reached by means of hormonal drugs (vasopressin, 9 alphafluodrocortisones, etc.). In the readaptatsionny period apply the suits putting excessive pressure upon the lower half of a body, preventing deposition of blood and promoting its return to heart to maintenance of orthostatic stability. Positive preventive effect also some nonspecific actions — a hardening, uv radiation render breath by gas mixtures, oxygen-deficient, etc.

Bibliography Genin A. M. and Sorokin P. A. Long restriction of mobility as model of influence of zero gravity on a human body, in book: Probl, kosmich. biol., under the editorship of V. N. Chernigovsky, t. 13, page 9, M., 1969; Space Ziologiya's Bases and medicine, under the editorship of O. G. Gazen^O!.i M. Calvin, t. 2, book 1, page 324, M., 1975. bibliogr.' Tyavokin V. V. Gipodynamya and cardiovascular pathology, Saransk, 11)75, bibliogr.; Physiological problems of a detrenirovannost, under the editorship of A. V. Korobkov, M., 1970; Nu-podynamics andhypogravics, The physiology of inactivity and weightlessness, ed. by M. McCally, N. Y. — J*., 1968.

I. D. Pestov.