An example of RR interval time series (500 intervals) measured during supine rest and during low intensity exercise.

<p>An example of RR interval time series (500 intervals) measured during supine rest and during low intensity exercise.</p

Mean (95% confidence interval) for selected HRV indices at rest before (pre), and after 21 weeks of training (post) in the endurance, strength, combined strength and endurance training, and control group.

<p>HR, heart rate; SDNN, standard deviation of NN intervals; HFP, high frequency power; LFP low frequency power; LFP/HFP, ratio between LFP and HFP; CI_1–5, complexity index of multiscale entropy analysis over the scales of 1 to 5. Statistically significant changes were not observed.</p

Heart rate and heart rate dynamics during steady state exercise.

<p>Heart rate (HR, A), standard deviation of NN intervals (SDNN, B), high frequency power (HFP, C) and HR complexity index for the scales 1 to 2 (CI_1–2, D) measured at baseline (0) and after 10 and 21 weeks of endurance (E), strength (S) or combined strength and endurance training (SE) and in the control group (C). *significant change (P<0.05) compared to the baseline, **P<0.01, ***P<0.001.</p

Individual and the mean changes in the HR complexity index.

<p>The index for the scales 1 to 2 (CI_1–2) was measured during steady state exercise at baseline (pre) and after 21 weeks in the endurance training (E), combined strength and endurance training (SE), strength training (S) and the control (C) group. **significant change (P<0.01) compared to the baseline.</p