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Biomedical subjects

Iu A Koriak

Publications and source records attributed to Iu A Koriak.

10 recordsLinked to original sources
PubMed1997

[Skeletal muscle reaction in man to a decrease in gravitation].

Functional characteristics the triceps surae muscle were studied in sex subjects exposed for 7 days to decreased unweighting induced by "dry" immersion (DI). After DI, the maximal voluntary contraction was a significant reduced by 33.8%, and the electrically evoked tetanic contraction (Po), and the twitch tension (Pt) was not significantly changed (8.2 and 9.9%, respectively). The force deficiency increased by 44.1% (P < 0.01). The twitch time-to-peak did not change, and to half-relaxation decreased by 5.3%. The Pt:Po ratio was decreased by 8.7% (P < 0.01) after "dry" immersion. The muscle surface action potential increased by 18.8% (P < 0.01), and a decrease of the amplitude and the area by 14.6% (P < 0.05), and 2.8% (P < 0.01), respectively. A comparison of the electrical and mechanical alterations recorded in the muscle suggests that due to decreased functional demands there may be an alteration not only in peripheral processes associated with the contraction, but also in the central (motor) command to the acting apparatus. We suppose that among peripheral sites, intracellular processes of contraction play the major in the contractile impairment recorded during "dry" immersion.

Action Potentials↗
PubMedDate not supplied

[The effect of long-term bed-rest head-down-tilt hypokinesia on the functional properties of the human neuromuscular apparatus].

An influence of 120-days antiorthostatic (-6 degrees) hypokinesia (ANOH) on the functional properties of human m. triceps surae (TS) was investigated. After ANOH the maximal force and the maximal voluntary contraction of TS decreased on the average by 45.5% and 33.7%, respectively, and the maximal twitch response force--by 36.7% (P < 0.05-0.01). The value of force deficit increased on the average by 60.2% (P < 0.001), while a relative increase of the TS force contraction decreased in response to pair irritation (P < 0.05-0.01) as well as the velocity properties of TS after ANOH (P < 0.05-0.001). The rate of absolute (c.u.) tension development fell significantly in response to electrical nerve irritation and during voluntary contraction, while the force-velocity muscle properties according to relative (%) parameters remained unchanged. The fatiguability index of TS constituted the average 0.61 +/- 0.02 after ANOH as against 0.80 +/- 0.03 prior to it (P < 0.05). It is postulated the alterations of contractile properties of TS are due both to atrophic processes, muscle length change, condition of sarcoplasmic reticulum and to changes in the state of the central nervous system.

Adult↗
PubMedDate not supplied

[A comparison of the contractile properties of the muscles of the lower extremities in man].

The physiological features of two antagonistic muscle groups, the dorsiflexors and plantar flexors of the ankle, have been compared in 11 healthy subjects aged 15-17 years (+/- SE; 16 +/- 1.2 years). Contractile properties of plantar flexors of the foot, namely of tibialis anterior (TA) and extensors triceps surae (TS) have been estimated by mechanical parameters of voluntary and electrically evoked contractions. All test subjects exhibited tolerance to supramaximal force of electric stimulation of n. tibialis and n. peroneus profundus at a frequency of 150 impulses.s-1 (for TS) and 150 impulses.s-1 and 250 impulses.s-1 (for TA). TA displayed high velocity and force-velocity properties (p < 0.05-0.001); TS had high force parameters (p < 0.05-0.01). The magnitude of force deficiency observed during voluntary contraction of these muscles is lower in TA and higher in TS (p < 0.05). The results permit supposing that differences in contractile properties of the muscles under study depend on a various specific contribution of peripheral and CNS factors.

Adolescent↗