Figure 4: Sequential change in frequency domain of heart rate variability measures of the control subjects and football players at rest. Nu: normalized unit. Data are presented as medians (25%~75%). #p<0.05 vs. baseline measurement; *p<0.05 vs. counterpart of the control; †p<0.01 vs. counterpart of the control (Friedman repeated measure ANOVA on ranks with post hoc Student-Newman-Keuls test). nVLFP: Normalized VLFP; nLFP: Normalized LFP; nHFP: Normalized HFP; LHR: Low-/Highfrequency power Ratio.