To decrease the influence of postural sway during spinal measurements, an instrumented fixation posture (called G) was proposed and tested in comparison with the free standing posture (A) using the DTP-3 system in a group of 70 healthy volunteers. The measurement was performed 5 times on each subject and each position was tested by a newly developed device for non-invasive spinal measurements called DTP-3 system. Changes in postural stability of the spinous processes for each subject/the whole group were evaluated by employing standard statistical tools. Posture G, when compared to posture A, reduced postural sway significantly in all spinous processes from C3 to L5 in both the mediolateral and anterioposterior directions. Posture G also significantly reduced postural sway in the vertical direction in 18 out of 22 spinous processes. Importantly, posture G did not significantly influence the spinal curvature.

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Power spectral analysis of heart rate variability (HRV) has been estimated by means of a Fourier transform method at rest in seven healthy men and three women, during a 30-minutes steady state cycle exercise test at 40%, 50%, 60%, 70% and 80% respectively, of maximal heart rate reserve (MHRR) defined as (HRmax -HRrest). Total power (P T ) of HRV was divided into three separate components (P HF , P LF , and P VLF ). All four indices for HRV decreased significantly with increasing exercise intensity. The fractional P VLF (%VLF), VLF/LF ratio, and VLF/HF ratio increased significantly with increasing exercise intensity. On the contrary, %LF and %HF decreased significantly with increasing exercise intensity.The following conclusions were made: (1) the contribution of parasympathetic activity to the power spectrum of HRV decreases with exercise intensity; (2) the change in %VLF, VLF/LF ratio, and VLF/HF ratio respectively, can be used as indices of change in sympathovagal balance during exercise; (3) the change in the LF/HF ratio cannot be used during exercise as an index of change in sympathovagal balance, since a change in vagal activity effects predominantly both numerator and denominator of the LF/HF ratio.

Authors present a hardware and software which enable to enlarge the practical application of the method of spectral analysis of R-R intervals variability, used for the evaluation of heart rate regulation in which autonomic nervous system and sympathetic and vagal effects play an important role. This developing method, applied and veri'ed by many authors, is at present realized with the help of expensive monitoring Jystems, the fact preventing its more general use. To solve the problem, the authors used a microcomputer measuring system, type TF-3, with telemetric transfer of values of R-R intervals, equipped with a special software including the procedures of measuring, jiltration and calculation of parameters of spectral analysis. The results of analyses make it possible to depict and quanti& the manifestations of factors influencing the variability of heart rate, including the sympathetic and vagal effects and their relationship during the speci'ed functional load, drug application etc.

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