Author(s): GRONWALD, T., KOCK, H.2, RÖGLIN, L.3, MÖHLE, M.3, KIRCHER, E.4, HOOS, O.5, KETELHUT, S.6, Institution: MSH MEDICAL SCHOOL HAMBURG, Country: GERMANY, Abstract-ID: 398

INTRODUCTION:
The present study explored acute responses of heart rate (HR) variability (HRV) metrics and selected hemodynamic parameters during the recovery phase following two exercise bouts of different intensity. The main focus was to advance current research by incorporating the non-linear index alpha 1 of detrended fluctuation analysis (DFAa1), providing additional qualitative information about autonomic nervous system regulation and reorganization during passive recovery.
METHODS:
Recreationally active female (n=13) and male (n=13) participants (age: 24.8±4.0 years, body mass: 68.3±10.8 kg, height: 171.2±9.6 cm, habitual physical activity: 7.3±3.5 h/week) were included in the study. In a first session a graded exercise test was conducted to determine peak HR (HRPEAK) and peak oxygen consumption (VO2PEAK) for exercise intensity prescription. In a second and third session, participants completed an endurance training with moderate intensity (MOD) on a treadmill and an exergaming training with vigorous intensity (VIG) in a randomized and counterbalanced order. Before and up to 45 minutes after the respective exercise sessions, RR-interval and hemodynamic measurements (peripheral systolic, SBP; diastolic blood pressure, DBP; pulse wave velocity, PWV) were conducted (supine body position). Blood lactate concentration (BLC) was measured before and immediately after the exercise bouts.
RESULTS:
Internal load analysis of MOD vs. VIG revealed significant differences and appropriate prescription of intensity domains for mean %HRPEAK (~66% vs 86%), %VO2PEAK (~48% vs. 66%), as well as for blood lactate concentration (~1 mmol/l vs. 5 mmol/l). The present data showed significant main effects of time, intensity, and their interaction for all RR-interval outcomes, PWV, and SBP. Higher exercise intensity resulted in greater perturbations during recovery, delayed reorganization, and decreased values of linear HRV metrics. DFAa1 demonstrated a stronger correlated reorganization and overcompensation after VIG, with higher values throughout the evaluated recovery process.
CONCLUSION:
The present data suggests that VIG transiently delays the recovery of cardiac parasympathetic activity and the normalization of correlation properties of HR time series. Regarding acute early and delayed recovery processes, higher correlation properties may reflect more order (less complexity) and interaction of involved physiological subsystems, supporting the assumption of increased systemic control to process the demands of higher exercise intensity. The assessment of standardized post-exercise (e.g., submaximal test procedures, benchmark workouts) linear and non-linear HRV metrics could serve as a valuable tool for fine-tuning monitoring processes in endurance athletes. By evaluating recovery states, acute fatigue, and overreaching phenomena it can complement resting physiology analysis. This could potentially help to guide structuring micro-cycle programming tailored to individual cardiac reactivation patterns.