Hrv analysis software premium version 3.2.0

A portable telemetric HR monitor system was used to record the resting HRV (Polar team Pro, Polar Electro, Kemple, Finland). Each player was issued an HR sensor and HR strap for the entire duration of the training camp. Kubios HRV analysis software (Premium version 3.2.0., Kubios, Kuopio, Finland) was used to calculate LnRMSSD. Artifact correction was set at a medium threshold level, and the window width was set at 300 s with a window overlap of 50%. Smoothing priors set at 500 Lambda were used for detrending methods (Tarvainen et al., 2014 (link)). If the percentage of ectopic beats in daily measure were >5%, then the data was excluded from the analysis.

ECG lead set (SS2LB, Biopac Inc., Goleta, CA, USA) with a conventional lead II arrangement was used to record cardiac responses in a supine position. A data acquisition system (MP35, Biopac Inc., Goleta, CA, USA) was used to collect resting ECG signals for 10 min before warm up and 30 min immediately after the RSA and YYIR1 exercise protocols. The analog signals of ECG were transformed into digital signals by using an analog-to-digital converter with a sampling rate of 1000 Hz via the Biopac Student Lab system. The ECG waveforms were then filtered using Kubios HRV analysis software Premium version 3.2.0. (Kubios, Kuopio, Finland) to calculate the time-domain and frequent-domain HRV indices. The artefact correction of RRI was set at a threshold of medium level, and window width was set at 300 s, with window overlap of 50%. Smoothing priors set at 500 Lambda were used for the detrending method [30 (link)]. The area-under-the-curve of the spectral peaks within the range of 0.04~0.15 Hz and 0.15~0.40 Hz were set for LF and HF, respectively. The power spectra of RR intervals were calculated by means of Fast Fourier Transformation.