The authors evaluated the heart rate variability (HRV) in 206 subjects (100 girls and 106 boys) with a mean BMI of 21.3 ± 2.3 by spectral analysis using the Varia-Pulse TF3 system (SIMA MEDIA, Olomouc). All subjects were examined under standard condition in a supine position. As to HRV parameters the following were evaluated: R-R interval, MSSD (mean squared successive difference), total spectral power, spectral powers in three frequency zones (VLF, LF, HF) and the VLF/HF ratio. HRV parameters and sex: By comparison of the mentioned parameters in the whole group no significant differences were found between boys and girls. Girls at the age of 15 years had as compared with boys of the same age significantly higher parameters of HRV (MSSD, total power, VLF power, HF power). At the age of 19 years girls had significantly shorter R-R intervals and lower values of HRV parameters. HRV parameters and age (15 - 19 years): In boys the length of the R-R interval increased significantly with age, i.e. the heart rate declined. Parameters characterizing the total HRV (total spectral power and MSSD) as well as spectral powers in the very low frequency (VLF) and high frequency zones (HF) increased with age. In girls in the mentioned parameters no developmental trends were observed.

        Key words: heart rate variability, spectral analysis, development, sex, age, young people