Confiabilidade da variabilidade da frequência cardíaca durante caminhada e repouso em diferentes posturas

Abstract

Heart rate variability (HRV) is a non-invasive method of autonomic nervous system (ANS) evaluation that reflects the ANS influences on cardiac rhythm. HRV is widely used and can be recorded in different conditions (e.g. exercise, rest, supine, seated, standing) depending on the application intended context. However, several physiological and environmental factors affect HRV values and may affect its reliability. HRV reliability and associations with physiologic and behavioral aspects were previously investigated, in different populations, recording conditions, and temporal scales. However, the traditional ways of reliability and associations investigation may have underestimated the measurement errors or sensibility of HRV, by using only two days in reliability comparisons and by using only one day in correlational analysis. Thus, the present study recorded HRV for five days, in four experimental conditions (walking, supine rest, seated rest, and standing), in a sample of 34 healthy young adults (19 men, ~22±4 years). Aerobic fitness (VO2max), bod fat percentage (Fat%), and habitual physical activity (EE, and MVPA) were also recorded for correlational analysis with five days mean of HRV measures. Good to moderate reliability was achieved during supine rest and walking recordings, while moderate reliability was achieved during seated and standing recordings. Except for SampEn, and DFAα1 nonlinear HRV metrics, that presented poor reliability in almost all recording conditions. VFC associations with VO2max, Fat%, EE, and MVPA were observed in all recording conditions, with higher correlations during walking. HRV reliability values of the present study were lower than the previously reported, while magnitude of associations in present study were higher than the previously reported. The studied population and the number of recording days seems to be the main factors impacting on reliability values, while the averaging of five-day recordings of HRV seems to be a superior method to improve sensibility of associations in this population. SDNN and HF during supine rest, RR and LF during walking recordings showed to be the best alternatives for the daily monitoring of HRV, while SampEn and DFAα1 didn’t presented adequate reliability for this purpose.