We recorded RR intervals through the RS800CX HR monitor, which had a sampling rate of 1 kHz. The RR intervals were transferred to the Polar Precision Performance program (v.3.0, Polar Electro, Finland). The Polar HR monitor distinguishes all heart beats in the left ventricular cardiac muscle and records the data, transferring the signal to the computer through a wireless infrared methodology. The Polar ProTrainer software allows the visualization and the removal of the RR interval file in “txt” format.
Specifics of the HRV analysis have been supplied previously16 (link),17 (link) and were in accordance with the directives from the Task Force13 (link).
To study the parasympathetic regulation of HR we inspected the high frequency band of spectral analysis (HF: 0.15 Hz to 0.4 Hz) in absolute units in the frequency domain, RMSSD (root-mean square of differences between adjacent normal RR intervals) in the time domain and the SD1 Poincaré plot (standard deviation of the instantaneous variability of the beat-to-beat heart rate). We applied the Kubios® HRV v. 2.0 software to compute these indices18 .
Specifics of the HRV analysis have been supplied previously16 (link),17 (link) and were in accordance with the directives from the Task Force13 (link).
To study the parasympathetic regulation of HR we inspected the high frequency band of spectral analysis (HF: 0.15 Hz to 0.4 Hz) in absolute units in the frequency domain, RMSSD (root-mean square of differences between adjacent normal RR intervals) in the time domain and the SD1 Poincaré plot (standard deviation of the instantaneous variability of the beat-to-beat heart rate). We applied the Kubios® HRV v. 2.0 software to compute these indices18 .
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