Effect of Lower Body Negative Pressure on the Heart Rate Variability

The R-R intervals were measured in 25 female volunteers aged 21–34 years after exposure to lower body negative pressure (LBNP). A number of advantages of information entropy (h) as an index of cardiovascular performance were revealed. With h used as a controlled variable, it was possible to ensure individual targeted changes in the functional state (FS) during LBNP. It was found that an individual exposure to LBNP caused regular changes in h and FS. Equations for targeted changes in human FS were derived.__________Translated from Fiziologiya Cheloveka, Vol. 31, No. 4, 2005, pp. 61–64.Original Russian Text Copyright © 2005 by Gerasimov, Ignatov.