Pavel Stejskal

Change in performance in response to training load adjustment based on autonomic activity.

The primary aim of this study was to assess performance (Perf) changes in response to a new training strategy. Specifically, based on spectral analysis of heart rate variability (SA HRV) to determine autonomic nervous system (ANS) activity, training doses were adjusted to maintain vagal activity at a high and relatively stable level during training preparation. Trained athletes (5 male and 5 female) aged 23.2±4.2 years voluntarily participated in the study. ANS activity was assessed during an orthoclinostatic test, and was represented by calculating HRV variables and a total score index. Over 17 weeks, improvement (1.4-8.5%) and deterioration (0.1-8.8%) in Perf were detected in 7 and 3 athletes, respectively. A relationship (rs=0.684; P<0.05) between the change in Perf (ΔPerf) and supine PHF during season was found. Supine HRV indices (PHF, PT, and MSSD) for the last 3 weeks of the HRV-adjusting period correlated (rs=0.636; 0.648; 0.648, P<0.05) with ΔPerf. Based on the results, a high and relative stable vagal activity during preparation may indicate a readiness to train or appropriate recovery that positively affects Perf. In conclusion, daily quantification of ANS activity by SA HRV seems to be a promising tool for the enhancement of Perf.

Vagal Threshold Determination. Effect of Age and Gender

Progressive increases in exercise intensity cause significant decreases in vagal activity (VA) until a critical point called the vagal threshold (TVA) is reached. This is where further increases in exercise intensity cause negligible change in VA. This study was designed to develop the algorithm for the TVA determination and to assess the effects of age and gender on its level. The sample consisted of 40 subjects who were divided according to age and gender into 4 groups with 10 subjects each: G1-Men age 25-31, G2-Men age 40-57, G3-Women age 24-28, and G4-Women age 43-56. The vagal responses were assessed by spectral analysis of the heart rate variability method while walking on a treadmill in a steady-state at intensities of 20-70% of the maximal heart rate reserve (MHRR). The mean intensity of 45% MHRR was suggested as the TVA level which is related neither to age nor gender. Heart rate related to TVA (TVA-HR) was affected by gender. High frequency power at TVA was influenced by age. The TVA-HR was considered to be a promising tool for the prescription of a safe level of physical activity for subjects with higher risks of health complications involving elevated sympathoadrenal activity during exercise.

Power spectrum of heart rate variability in exercising humans: The effect of exercise intensity

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 (PT) of HRV was divided into three separate components (PHf, Plf, and Pvlf). All four indices for HRV decreased significantly with increasing exercise intensity. The fractional Pvlf (%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.

Cardiac autonomic modulation before parachuite descent

Experiences resulting from multi-repetitions of parachute descents can reduce the changes in the cardiac autonomic modulation even in such a stressful situation as leaving the airplane.