Changes of the individual heart rate variability under stress for college students with different level of resilience

Objective To study the changes of heart rate variability (HRV) in the Trier Social Stress Test (TSST) among the college students with different level of resilience. Methods Connor-Davidson Resilience Scale (CD-RISC) were used to test the resilience of 160 students in a Military Medical University, and according to the test results, 11 male students with high resilience and 11 students with low resilience were selected to participate the TSST experiment. The test were done according to the TSST standard procedures, heart rate (HR) and HRV were recorded 3 times (before and after the 1st and 25th minutes of TSST). Results ①The low-resilience group’s HR and HRV index were lower (including HRV VLF, LF and HF) than those in high resilience group(P<0.01). ②Compare with the HR baseline values, the HR peaked within the 1st minute of TSST and gradually reduced. The HR ((6.09±8.87)/min) evidently increased in the low-resilience group at the 1st minute (P<0.05). The VLF and HF powers of HRV in the high-resilience group were lower on the 1st minute and significantly higher on the 25th minute (VLF=(15.61±11.81)Hz, HF=(5.48±7.99)Hz, P<0.05). The LF ((84.92±13.30)Hz) power was significantly higher on the 1st minute and peaked on the 25th minute ((89.72±14.93)Hz, P<0.01). The LF/HF ratio (3.43±0.76) increased on the 1st minute and then gradually decreased (1.26±0.23, P<0.01). The VLF, LF and HF powers of HRV in the low-resilience group were significantly higher on the 1st minute. The VLF and LF power continued to increase and they peaked on the 25th minute, whereas the HF power significantly decreased to a minimum on the 25th minute (P<0.01). Within the 1st minute of the experiment, the LF/HF ratio (0.45±0.27) decreased and then gradually increased (1.91±0.40, P<0.01). Conclusion Under stress, individuals with higher resilience have higher HRV to cope with stress effectively and recover quickly. Key words: Heart rate variability; Resilience; Stress