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Objective To investigate the effect of exposure to positive acceleration on heart rate variability (HRV). Methods A single-arm trial was conducted on 12 participants who have a flight duration of >300 h were subjected from a same training batch between July 23 and 25, 2023. They were exposed to overloading with a peak value of +3.5 and +4.25 Gz for a duration of 10 s respectively on a manned centrifuge. Heart rate, respiratory rate, and time-domain and frequency-domain indicators of short-term HRV under exposure to overloaded positive acceleration were collected, recorded and analyzed. Results Under the overloaded +3.5 and +4.25 Gz positive acceleration for 10 s: ① The heart rate was 135.42±14.78 and 143.92±14.47 beats/min, the respiratory rate was 23.57±4.09 and 26.80±4.71 breaths/min, respectively, and both rates were significantly higher than those before exposure (97.08±14.61 beats/min and 14.86±2.06 breaths/min, P < 0.01); ② The time-domain indicator, root mean square of difference between successive normal RR intervals (RMSSD), was 7.69±4.32 and 6.84±3.41 ms respectively under +3.5 and +4.25 Gz positive acceleration, and both rates were obviously lower than before exposure (13.14±6.37 ms, P < 0.05); ③ The frequency-domain indicator, high frequency (HF) was 20.53±8.80 and 16.04±7.19 ms2, respectively, and both were obviously lower than those before exposure of (44.07±24.67 ms2, P < 0.05); another frequency-domain indicator, low frequency (LF) was 38.07±19.72 and 42.46±17.08 ms2 respectively, but the values had no statistical difference with the value before exposure (26.33±19.10 ms2, P>0.05); ④ The LF/HF ratio of the 2 exposure doses was 4.02±1.52 and 5.32±1.86 respectively after expose, and 0.67±0.32 before exposure, and a significant increase was observed (P < 0.05). Conclusion Positive acceleration exposure significantly affects heart rate, respiratory rate, and HRV time- and frequency-domain indicators RMSSD, LF/HF, and HF. Our results suggest that the exposure leads to increased tone in human sympathetic nerve and significant increment in HRV. |
