Hrv logger app

R‐R intervals (RRI) were assessed by means of the POLAR H10 chest strap (Polar Electro, Finland) with a RRI resolution rate of 1 ms, recorded with the HRV Logger App (HRV Logger, Marco Altini). The Polar H10 derives RRIs from an inbuilt ECG processor and has been validated against a 3‐lead ECG Holter, exhibiting equal precision during rest and more accurate RRI detection during exercise, thus suggesting valid RRI assessment (Gilgen‐Ammann et al., 2019 (link)). RRIs were imported to KUBIOS Premium (V. 3.5.0) to analyze HRV (Tarvainen et al., 2014 (link)). The RRI time series was visually inspected and the inbuilt KUBIOS filter (automatic correction) was applied when necessary (Lipponen & Tarvainen, 2019 (link)). RMSSD and LF‐HRV (Fast Fourier transform) as reliable indicators of CVA during slow‐paced breathing were assessed (Kromenacker et al., 2018 (link); Laborde et al., 2017 (link); Shaffer & Meehan, 2020 (link)). While RMSSD provides a global measure of CVA, LF‐HRV emphasizes the baroreflex‐related HR oscillations, expressing the unique respiration‐driven stimulation of the cardiovascular system during RB (Shaffer & Meehan, 2020 (link)).