Figure 3. Differences in (A) RMSSD, (B) SDNN, (C) HF(ms2), (D) LF/HF, (E) SampEn and (F) DFAα1 of heart rate variability (HRV) between the hydrogen-rich water (hw) and placebo water (pw) trials across the experimental timeline. RMSSD = Square root of the mean squared differences between successive RR intervals, SDNN = Standard deviation of RR intervals, HF(ms2) = high‑frequency power, LF/HF = Ratio between LF and HF band powers, SampEn = Sample entropy, DFAα1 = in detrended fluctuation analysis, short term fluctuation slope, Before = before exercise, During = in motion, After = within 5 minutes after exercise, After10min = 10min after exercise. *p < 0.05.