Table 3. Results of mixed ANOVA with the associated p values of the HRV at REST, T0, T12, T24 in relation to morning and evening session of HIIT related to M-types and E-Types. Effect of time M-Type vs E-Type Interaction Morning Training HR rest (bpm) p < .0001 p < .0001 n.s. Ln RMSSD (ms) p < .0001 p = .0005 n.s. Ln LF power (ms2) p < .0001 p < .0001 n.s. Ln HF power (ms2) p = .0140 p = .004 n.s. LF (n.u.) p < .0001 p < .0001 n.s. HF (n.u.) p < .0001 p < .0001 n.s. α1 DFA p < .0001 p < .0001 n.s. Evening Training HR rest (bpm) p < .0001 n.s. n.s. Ln RMSSD (ms) p = .003 n.s. n.s. Ln LF power (ms2) p < .0001 n.s. n.s. Ln HF power(ms2) p = .038 n.s. n.s. LF (n.u.) p = .011 n.s. n.s. HF (n.u.) p = .007 n.s. n.s. α1 DFA p = .0002 n.s. n.s. HR: heart rate; RMSSD: square root of the mean of the sum of the squares of differences between adjacent normal R–R intervals; LF: low frequencies; HF: high frequencies; DFA: detrended fluctuation analysis; n.s.: not significant