Research on Influence of Repeated Body Position Changes on Human Head-down Tilt Tolerance and Its Duration

Gong Xianwen; Liu Min; Wu Ping; Wu Bin; Sun Hongyi; Huang Weifen

doi:10.16289/j.cnki.1002-0837.2018.02.016

Abstract：Objective To verify the influence of a 5-day repeated body position change training on human headdown tilt(HDT) tolerance, and how long it will maintain. Methods Seventeen young healthy male subjects were trained with repeated position change once a day for 5 days. The HDT tolerance tests were carried out on the day immediately before the first training, the 1st day, the 7th day, the 14th day and the 28th day after the last training respectively, during which the subjective feelings and the symptoms, blood pressure, some cardiac parameters, the total peripheral resistance(TPR) and the salivary cortisol were monitored. Results Compared with the day before the first training, scores of subjects'sensation and symptom during the HDT tests after training increased but with no significance. The systolic blood pressure(SBP), diastolic blood pressure (DBP) and mean arterial pressure(MBP) during HDT test on the first day after training decreased significantly(P ＜ 0.05, P ＜ 0.01). The first 10 s of the SBP during HDT test, the three 10 s of the DBP and MBP during HDT test on the 7th day after training decreased but without significance. The supine SV on the 1st, 7th, and 28th day after training decreased significantly(P ＜ 0.05), while changes of other cardiac parameters were not significant. TPR during HDT test on the 1st day after training decreased significantly(P ＜ 0.05). TPR during HDT on the 7th day after training decreased, but only of significance in the second 10 s(P ＜ 0.05). TPR during HDT test on the 14th day changed insignificantly. The second 10 s of TPR during HDT test on the 28th day after training increased significantly. All the salivary cortisol changed insignificantly. Conclusion Five days repeated body position change training could improve the subjective sensations and the symptoms during HDT test. The HDT tolerance was improved by the decrease of the blood pressure which was realized by the decrease of the TPR. The influence of 5 days repeated body position change training on human HDT tolerance will maintain for about 1 week.