All data are presented as mean ± standard deviation from 10 consecutive heart cycles with a significance level of P-value <0.05. The collected data were analysed by two-way repeated-measures analysis of variance (ANOVA) using group and repetitive heart cycles as factors. The model allowed for different residual variations in the groups. Residuals were inspected for normality by QQ-plots and residuals versus fitted values and no reason to refute was found. Groups were then compared using post hoc Wald z-tests. No corrections were performed for multiple testing. Heart rate was compared between groups using a paired t-test. The data were analysed using Stata 13.0 (StataCorp LLC, College Station, TX, USA), and the statistical models were performed with support from Biostatistical Advisory Service, University of Aarhus, Denmark.