, Volume 37, Issue 6, pp 755-762
Date: 27 Nov 2011

Ontogenetic model of gravity and weightlessness: Theoretical and applied aspects

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Abstract

The review discusses the previously postulated natural adaptive motor strategies evolving during the human life span and their link to sensory conditions, among which gravity and temperature play the predominant role. The initial FM strategy based on the dominance of fast-twitch motor fibers is characteristic of intrauterine immersion in the amniotic fluid and microgravity in a real space flight (G∼0). According to this paradigm, the process of parturition when the newborn experiences a sensory attack of Earth’s gravity (1G) and a lower temperature can be considered equivalent to an astronaut’s landing. This postnatal GE strategy is opposite to the FM strategy, because it decreases the motor unit (MU) firing and causes the activity of muscle fibers to slow down. The next SJ strategy appears in normal aging, which is expressed in further dominance of slow-twitch MU and discreet motor control, thus stimulating hypergravity (>1G). Cooling evokes similar adaptive reactions. The synergy of sensory inputs acting upon the motor system within the strategies suggests the possibility of their mutual substitution. For example, a moderate sensory cold attack may serve as a partial surrogate of gravity (∼0.2G), which could be used as a countermeasure for the unfavorable effects of a long-term space flight.

Original Russian Text © A.Yu. Meigal, 2011, published in Fiziologiya Cheloveka, 2011, Vol. 37, No. 6, pp. 130–138.