Mental stress recognition using interpretable machine learning models with heart rate variability among Chinese university students

Figure 2 Significant differences in the heart rate variability parameters between the stress and control groups among Chinese university students. Significance level was set at P < 0.05. ^aP < 0.05; TSP: Total power spectrum; TDI: Time domain index; FDI: Frequency domain index; SDNN: Standard deviation of NN intervals; SDNN5: 5-minute mean of standard deviation of NN intervals; VLF: Very low frequency; TP: Total power; DPTI/SPTI: Diastolic/systolic pressure-time index of the heart; C1: Compliance of arterial vascular volume; AI: Augmentation index; EEI: Ejection elasticity index.