[Effect of long-term hypokinesia on cardiac/bioelectric activity in healthy men]

Bioelectric activity of the heart was measured in 39 healthy men, aged 25 to 45 years, during their exposure to head-down tilt. The first experimental study which continued for 182 days (-4.5 degrees) was performed on 18 test subjects, and the second study which lasted for 120 days (-4.5 degrees) on 21 test subjects. Both studies included controls (15 subjects) and subjects who exercised during head-down tilt (16 subjects). In addition, the second study also included 4 test subjects who took drugs to modify metabolic shifts and 4 test subjects who were in the drugs + exercise regiment. Prolonged hypokinesia led to a heart rate increase, A-V conductance decrease, and repolarization phase (T-wave) changes. Except for heart rate variations, these changes developed beginning with the first weeks of exposure, plateaued during 1.5 to 2 months and then varied in a sinusoidal manner, coinciding with similar changes in blood neurotransmitters and electrolytes. T-wave changes correlated well with K, Mg and Ca variations in blood. Exercises performed during head-down tilt decreased significantly (1.5-2 times) the level of T-depression and accelerated the restoration of ECG parameters during readaptation. Corinfar taken for two weeks had a noticeably beneficial effect on electrophysiological processes of the heart. The above electrophysiological changes that developed in healthy men during prolonged hypokinesia were of functional, reversible character and disappeared within the 2-month recovery period.