The autonomic nervous system (ANS) is a crucial participant of the complex neuro-endocrine conservation of energetic homeostasis. Furthermore, ANS activity could serve as an indicator of appropriate physiological condition for aerobic training. Therefore, the major goal of this study was to explore whether parameters of HRV, as a marker of ANS-activity. are related to functionality and power of fat metabolism during exercise. n = 26 healthy trained men (age: 24,5 ±3,1 a; VO²max: 54 .7 ± 4,1 ml/(min*kg)) performed one graded treadmill running test to exhaustion (GXT: start: 6 km/h; every 3 min plus 1 km/h), a measurement of resting HRV during an orthostatic stress test and one Fatmax-Test (5 stages à 3 min, individual velocities) to determine the exercise intensity at which fat oxidation rate is maximal. Blood lactate and ventilation were measured during both exercise tests while RR-Intervals were recorded during the orthostatic stress test. Significant relations between parameters of the Fatmax-Test (Fatmax, Power@Fatmax, aVO2@Fafrnax, % VO2max@Fatmax) and HRV during the orthostasis test (RR, SDNN, RMSSD, LF, HF. Alpha1, SampEn) were assessed by bivariate pearson correlations, while the orthostatic shift in autonomic activity was test by student's t-test for paired samples. The high baseline HRV during supine rest indicating strong vagal activity was significantly (p < 0,01) shifted towards an enhanced sympathetic heart rate modulation during the upright position. During the GXT a maximal fat oxidation rate (FOR) of 40,4 ±10,1 g/h was attained at a velocity of 8,5 ± 0,8 km/h while eliciting 57 ± 6% of VO²max. Significant correlations between HRV-measures during supine rest and fat metabolism were only detected for RMSSD and Power@Fatmax (r = 0,42) and SampEn and Fatmax (r = -0.42). On the other hand, the upright position induced consistent significant (p < 0.05) positive correlations between % VO2max@Fatmax and time and frequency domain measures (SDNN: r = 0,46, RMSSD: r = 0,43. LF: r = 0,42. HF: r = 0.48). In addition, a moderate relation between SampEn and VO2@Fatmax (r = 0,55) and Power@Fatmax (r = 0,45) was detected. The results indicate, that possible interactions between vagal activity and complexity of HRV and fat metabolism during exercise can only be detected in a situation of mild orthostatic stress. This might be related to saturation effects of HRV-measures of vagal activity in relation to RR-intervals during supine rest of trained subjects. Further research is warranted to explore whether high vagal activity and complexity of HRV might play a beneficial rate for fat metabolism during exercise.
© Copyright 2011 Herzfrequenzvariabilität: Gesundheitsförderung - Trainingssteuerung - Biofeedback. Internationales Symposium am 29. und 30. Oktober.. Veröffentlicht von Feldhaus, Ed. Czwalina. Alle Rechte vorbehalten. / Übersetzt mit https://www.DeepL.com/Translator