Author(s): MARTINS BERNAL, J., COUTO, N.M.S., FACIOLI, T.P., SANTOS, D., SOUZA, H.C.D., Institution: UNIVERSITY OF SÃO PAULO, Country: BRAZIL, Abstract-ID: 1406

INTRODUCTION:
COVID-19 has been associated with persistent alterations in the autonomic modulation of heart rate variability (HRV). However, it remains poorly understood whether disease severity during the acute phase affects the magnitude of these alterations. On the other hand, aerobic physical training (APT) has been proposed as a countermeasure to impairments in the autonomic modulation of HRV in different conditions; however, its effects are not yet well established in relation to COVID-19. Therefore, the objective of this study was to investigate the consequences of COVID-19 on the autonomic modulation of HRV according to disease severity and to evaluate the effects of APT on this parameter.
METHODS:
One hundred and sixteen individuals aged between 30 and 55 years were included, allocated into three groups according to the severity of the disease in the acute phase: Mild group (n=38); Moderate group (n=52) and Severe group (n=26). All groups had anthropometric and hemodynamic parameters evaluated before and after the 16-week APT period, as well as parameters of autonomic modulation of HRV analyzed using linear (time and frequency domain) and non-linear (symbolic analysis) methods obtained from R-R interval (iRR) recordings in the supine position for 30 minutes.
RESULTS:
Initially, all groups presented similar anthropometric and hemodynamic values. In contrast, the Moderate and Severe groups presented lower values for standard deviation of normal iRR (SDNN), root mean square difference between adjacent normal iRR (RMSSD), total variance, and high-frequency (HF) oscillations in absolute units, both compared to the Mild group. In turn, the Severe group, when compared to the other groups, also presented lower HF oscillations and higher low-frequency (LF) oscillations, but in normalized units. After the 16-week APT, all groups showed increases in HF oscillations and reductions in LF oscillations, both in absolute and normalized units. In this case, there were no further differences in LF and HF oscillations between the groups.
CONCLUSION:
Individuals who had COVID-19 and developed moderate to severe cases showed greater impairments in the autonomic modulation of HRV, characterized by increased sympathetic autonomic modulation and reduced vagal modulation. In turn, APT as a countermeasure appears to increase vagal autonomic modulation and reduce sympathetic autonomic modulation of HRV, regardless of the previous severity of COVID-19.