Table 4.

Inter-correlations (Pearson’s R values) of physiological biomarkers of stress

	1	2	3	4	5
1. HR reactivity	–
2. HR recovery	0.88**	–
3. SDNN reactivity	− 0.18	− 0.32†	–
4. SDNN recovery	− 0.30	− 0.39*	0.49**	–
5. Alpha-amylase change	− 0.19	− 0.07	− 0.32†	− 0.01	–
6. Cortisol change	0.14	0.11	0.07	0.04	0.19

HR heart rate, SDNN standard deviation of NN intervals

*p < 0.05, **p < 0.01, ^†p < 0.09