振动锻炼和太空养心丸对60 d头低位卧床脑血流的影响

目的 通过观察和比较60 d头低位(HDT)卧床期间振动锻炼、中药太空养心丸对脑血流的影响,进一步明确不同对抗方式对失重不良影响的对抗效果. 方法 21名健康男性志愿者,随机分为对照组、振动组和中药组3组,每组7人.对照组仅-6°HDT卧床60 d,口服安慰剂;振动组和中药组在HDT卧床期间分别进行阻抗振动锻炼和口服太空养心丸.卧床前、卧床第30天、第60天测量右侧大脑中动脉的血流速度. 结果 对照组的收缩期血流速度(Vs)在卧床第30天较卧床前显著降低(t=3.44,P<0.05),并且在第60天进一步降低t=5.07,P<0.01);舒张期血流速度(Vd)、平均血流速度(Vm)在卧床第60天显著降低(t=2.61、7.20,P<0.05).振动组的Vs在卧床第30天显著降低(t=2.49,P<0.05),并且在卧床第60天进一步降低(t=3.49,P<0.01);中药组Vs、Vd和Vm有降低趋势,但未达显著水平. 结论 60d头低位卧床可引起大脑中动脉血流速度显著降低.卧床期间服用太空养心丸对改善脑血流有一定作用,而振动锻炼则对脑血流影响不大.     

利用非线性方法研究头低位卧床对心血管调控机制的影响(英文)

目的本研究旨在用非线性分析方法,探讨-6°头低位卧床试验对心血管调控机制的影响,并将对照组和中药组进行比较。方法 14名男性健康志愿者随机分入对照组和中药组,进行60d的头低位卧床试验。在试验前、中、后,运用非线性分析技术对心率变异、血压变异进行测试。结果志愿者心率水平在卧床开始后的前21d保持稳定,但从卧床试验的第41天起显著升高,且在卧床结束后亦未恢复至正常;趋向波动指数(DFAα1)于卧床试验开始后的第2天出现明显升高,且维持升高状态至试验结束后的第12天;混沌指数(chaos)在卧床过程中明显下降。卧床试验过程中组间对比发现:对照组心率变异的1/f以及血压变异的SDNN、LF/HF、DFAα1和1/f明显高于中药组,并且心率变异的DFAα2和血压变异的HF明显降低。结论在卧床试验后期机体出现迷走神经张力下降,迷走交感平衡升高;而中药可以减轻模拟失重对心血管系统的影响。     

60d-6°头低位卧床指端光电容积波的形态变化分析

目的 提出光电容积波(PPG)形态度量的6种新指标,用于分析中短期模拟失重引起的指端PPG的形态变化.方法 实验分为卧床前15 d(基准期)、-6°头低位卧床60 d(卧床期)与卧床结束后15 d(恢复期).21名男性健康志愿者随机分为对照组、阻抗振动组、中药防护组,每组7人.检查了卧床前第6天(-6 d)、卧床第52...     

长期头低位卧床实验全周期个体情绪变化过程研究

目的 在90 d头低位卧床(HDBR)条件下对个体情绪变化进行全周期追踪评估.方法 以完成90 d-6°HDBR实验的36名男性志愿者为对象,志愿者按照锻炼方案分为5组,测评全周期为135天,分预适应期(卧床前15天)、严格卧床期(HDBR 90天)、恢复期(卧床后30天)三阶段,评估进程中志愿者的焦虑、抑郁、心境状态...     

4d头低位卧床期间脑血流速度的改变

目的观察 4d头低位卧床模拟失重期间大脑中动脉血流速度的变化。方法 8名健康男性志愿者进行 4d - 6°头低位卧床试验。卧床前和卧床 4d结束时在倾斜床上进行 2次立位耐力检查 ,卧床前(卧位 )、卧床第 1、3、4天及起床后第 2天用经颅多普勒超声仪测量右侧大脑中动脉血流速度。结果 4d卧床结束时 ( 87.5 % )被试者立位耐力不良发生率较卧床前 ( 37.5 % )显著增加 (P <0 .0 5 )。大脑中动脉收缩期血流速度、舒张期血流速度和平均血流速度在卧床第 1、3天较卧床前均有降低趋势 ,但未达到显著水平 ,卧床第 4天均显著降低 (P <0 .0 5 ) ,起床后第 2天基本恢复。在卧床期间 ,平均动脉压及舒张压均显著升高 (P <0 .0 5 ) ,体重显著降低 (P <0 .0 5 )。结论 4d头低位卧床可引起大脑中动脉血流速度显著降低 ,立位耐力不良发生率增加。脑血流速度降低可能是失重 /模拟失重致立位耐力不良的机制之一     

15d-6°头低位卧床对女性最大咬合力及咬合速度的影响

目的 观察-6°头低位卧床(HDBR)对女性志愿者最大咬合力及咬合速度的影响.方法 应用T-ScanlI咬合力分析系统记录20名女性志愿者在4个时间点:卧床前、卧床第4天、第10天及恢复期第7天的最大咬合力以及达到最大咬合力所需时间,并对所得数据进行配对t检验分析.结果 女性志愿者最大咬合力在卧床后第4天[(2219....     

30d头低位卧床对男性牙龈色彩的影响

目的研究头低位卧床模拟失重对健康人牙龈颜色的影响。方法采用﹣6°头低位卧床模拟失重,在5个时间点:卧床前第3天(HDBR-3)、卧床第10天(HDBR 10)、卧床第20天(HDBR 20)、卧床第30天(HDBR 30)和恢复期第3天(HDBR+3)检测游离龈和附着龈的色彩。结果与卧床前相比,男性志愿者牙龈游离龈、附着龈的L*值在卧床第20天、30天显著升高(P<0.05),在卧床第10天、恢复期第3天无显著性差异;游离龈和附着龈的a*和b*值在卧床第20天、30天和恢复期第3天非常显著升高(P<0.01),在卧床第10天无显著性差异。结论失重环境可使人体游离龈、附着龈发生炎症反应。为降低失重对人体口腔软组织的影响,在航天员的日常训练和航天实验过程中应加强口腔组织的卫生防护。     

15d-6°头低位卧床对女性抑制功能的影响

目的 探讨-6°头低位卧床模拟失重对女性抑制能力的影响.方法 志愿者分为接受头低位卧床实验的卧床组和不参加卧床的对照组,采用数字Stroop任务测试两组志愿者在卧床实验前5天、卧床第5天、卧床第10天以及卧床后第5天的抑制能力,并采用贝克焦虑量表和Beek抑郁量表同步记录各测试时间点志愿者的抑郁和焦虑情绪.结果 卧床第...     

21天卧床对人体自发性压力感受器—心率反射的影响

目的研究模拟失重对人体自发性压力感受器－心率反射反应性的影响及其与立位耐力的关系。方法利用Ｆｉｎａｐｒｅｓ无创血压监测仪采集１５名男性青年２１天－６°头低位卧床期间及卧床前、后头高位倾斜试验时逐跳动脉血压信号，测量自发性压力反射反应斜率（ＰＲＳ）的变化。结果卧床期间，１５人中有１２人的平均ＰＲＳ值呈减小变化，其中有５人在卧床结束时未能完成２０ｍｉｎ头高位倾斜试验，其平卧位ＰＲＳ值１１４．８±２２．２ｍｓ／ｋＰａ较卧床前对照水平２０３．９±１９．５ｍｓ／ｋＰａ显著减小（Ｐ＜０．０５），并在头高位倾斜时进一步减小为６５．６±５．１ｍｓ／ｋＰａ。头高位倾斜试验完成者的平均ＰＲＳ值，在卧床前、后无显著变化。结论模拟失重可导致人体自发性压力感受器－心率反射反应性降低，其可能参与了立位耐力不良机制的产生。     

21d头低位卧床期间脑底动脉血流动力学的变化

目的观察21d头低位卧床期间脑底动脉血流动力学的变化。方法6名健康男性志愿者,年龄24.8±6.1岁,进行了21dHDT-6°卧床试验。HDT前、HDT第10天及卧床结束时进行了3次立位耐力检查。HDT前(坐位)、HDT即刻(D0)、第1、3、7、10、21天用经颅超声多普勒(TCD)测量了双侧大脑前(ACA)、中(MCA)、后动脉(PCA)的血流动力学指标。结果卧床第10天和卧床结束时,受试者立位耐力比卧床前显著降低(P<0.05）。卧床第3天和第21天的右侧MCA的V     

重力应激正自发性压力感受器—心率反射反应性的评定

为探讨重力应激下自发性压力感受器－心率反射反应性的评定方法，观察了１０人＋６５°头高位倾斜与８人－６．６７ｋＰａ下体负压作用下，以及１５人１６ｄ－６°头低位卧床期间ＢＲＳ的变化。     

Cardiovagal baroreflex and aortic hemodynamic responses to isometric exercise and post‐exercise muscle ischemia in resistance trained men

Arterial stiffness is associated with reduced baroreflex sensitivity (BRS) and resistance training; thus a potentially increased cardiovascular risk in resistance‐trained (RT) individuals. The effects of resistance training on arterial stiffness and BRS have been evaluated at rest, but cardiovascular abnormalities that are not shown at rest may be revealed during recovery after exercise. Aortic systolic (aSBP) and diastolic blood pressure (aDBP), stroke volume (SV), augmentation index (AIx), vagal activity, BRS responses to isometric handgrip (IHG), and post‐exercise muscle ischemia (PEMI) were evaluated in 10 RT and 10 untrained (UT) men (21±1 years). Resting aDBP and AIx were lower in RT compared with UT. Heart rate recovery, BRS, and vagal reactivation during PEMI were similar in both groups. Increases in aSBP (13±11 mmHg), AIx (5±10%), and SV (12±12%) during IHG further increased during PEMI (8±14 mmHg, 12±6%, and 10±8%). Increases in aDBP from rest to PEMI were higher in RT (17±9 mmHg) compared with UT (7±8 mmHg). The lower resting aDBP and the enhanced response to PEMI suggest beneficial adaptations in RT men. Wave reflection, aortic SBP, and cardiovagal BRS responses to IHG and PEMI are not affected by resistance training in young healthy men.     

21 d-6°头低位卧床期间运动训练对动态姿态平衡的影响

目的探讨21 d-6°头低位卧床和卧床运动训练对动态姿态平衡和控制功能的影响. 方法 10名健康男性青年被试者分为卧床对照组和卧床训练组,每组5人,卧床期间训练组每天进行2次、每次30 min逐级增加负荷的头低位功率自行车训练;分别于卧床前和卧床后21 d进行了动态姿态平衡和双膝等速肌力的测试. 结果与卧床前相比,对照组动态本体感觉得分和运动控制适应能力明显降低,双膝相对峰力矩明显降低,同时伴有腘绳肌与股四头肌峰力矩屈/伸比值的明显增加;训练组动态本体感觉得分和运动控制适应能力明显高于对照组,而腘绳肌与股四头肌峰力矩屈/伸比值无明显改变. 结论 21 d-6°头低位卧床运动训练能够明显改善卧床后动态姿态平衡及其动态运动适应功能.     

Bed rest affects ventricular and arterial elastances in monkeys: implications for humans

METHODS: Experimental data were obtained from five chronically instrumented rhesus monkeys exposed to 96 h of 10 degrees head-down bed rest (HDBR) and another 96 h of 80 degrees upright control separated by 9 d of ambulatory recovery in a counter-balanced, crossover experiment design to test the hypotheses that: 1) headward and footward fluid shifts would increase systemic arterial (Eart) and left ventricular end-systolic (Ees) elastances; and 2) changes in Eart and Ees would be related in magnitude and direction. Ees and Eart were calculated from measurements taken during five observation periods for initial 2-h and 4-d exposures to HDBR that produced headward volume shifts, and acute exposure to graded levels of lower body negative pressure (LBNP) designed to produce orthostatic volume shifts. RESULTS: There was no effect of HDBR on Ees and Eart for any observation period (initial 2-h, 4-d, or LBNP). Eart increased in a similar pattern during the 4-d exposure to both control and HDBR. Ees increased with increasing LBNP levels for both control and HDBR while Eart remained unchanged. CONCLUSION: Our data are consistent with the notion that elevated Eart may represent an adaptation to physical inactivity that is associated with cardiovascular deconditioning.     

Orthostatic tolerance and hormonal changes in women during 120 days of head-down bed rest

BACKGROUND: Women will be included as mission specialists in the upcoming International Space Station program. This paper describes the changes in volume-regulating hormones and determines the degree of degradation in orthostatic tolerance in a group of women after 120 d of bed rest. The aim of this study was to test a countermeasure program to be used by women during long-duration spaceflights. METHODS: For 120 d of -6 degrees head-down bed rest (HDBR), eight healthy women were assigned either to a no-countermeasure (No-CM, n = 4), or to a countermeasure (CM, n = 4) group. In the countermeasure group, exercise began after 2 wk, pharmacological agents were given during the 1st and 3rd mo, and the "Centaur" suit was worn on the last day of bed rest and during the day time for several days after bed rest. Diet supplements were taken during the 1st and 4th mo of HDBR. Tilt tests were run before and after HDBR. RESULTS: After the HDBR, none of the CM subjects, had pre-syncopal or syncopal symptoms during tilt tests: BP was well maintained in the CM group, while heart rate and BP changed in the No-CM group. In plasma, atrial natriuretic peptide (ANP) increased in both groups and remained high throughout HDBR, while aldosterone increased and remained elevated in the No-CM group. Natriuresis was decreased during HDBR. CONCLUSION: The CM protocols used during this study were efficient and prevented orthostatic intolerance for the four CM subjects. It would be necessary to obtain more data regarding this set of CM protocols on female subjects to lead to statistical and formal conclusions.     

Baroreflex sensitivity during static exercise in individuals with Down Syndrome

INTRODUCTION: Individuals with Down syndrome (DS) have altered heart rate (HR) and blood pressure (BP) responses to orthostatic challenges and isometric handgrip (IHG) exercise, suggesting possible alteration in baroreflex sensitivity. PURPOSE: This study investigated baroreflex sensitivity (BRS) as a potential mechanism contributing to chronotropic incompetence during IHG in persons with DS. METHODS: Heart rate and BP were continually recorded in 12 individuals with DS and 10 controls, at rest and during 2 min of IHG, at 30% of maximal voluntary contraction (MVC). Spontaneous BRS was derived via the sequence method. RESULTS: No differences were seen in HR at rest between groups. Systolic BP (SBP) was significantly lower in the DS group at rest (106.1+/- 2.9 vs 116.5+/- 3.9 mm Hg, P < 0.05) and during IHG (123.9+/- 4.6 vs 150.1+/- 5.3 mm Hg, P<0.001). A significant group-by-task interaction was found for both change in HR and change in SBP with IHG, because of an attenuated HR and SBP response to IHG in participants with DS (P<0.05). When controlling for resting SBP, the DS group had a lower BRS at rest (16.0+/-1.7 vs 21.2+/-4.2 ms.mm Hg, P< 0.05) and during IHG (7.8 +/-1.0 vs 12.1+/- 2.6 ms.mm Hg, P< 0.05). CONCLUSIONS: Individuals with DS have lower BRS at rest and during IHG than controls and this may be related to their attenuated HR response during perturbation.     

Baroreflex control of heart rate during heating in subjects with low orthostatic tolerance

BACKGROUND: Heat stress induces a reduction of orthostatic tolerance. The cardiovascular responses, including the cardiac baroreflex response to heat stress, were examined to test the hypothesis that subjects with orthostatically low tolerance demonstrate an impaired baroreflex control of heart rate (HR) during heat stress. METHODS: There were 44 healthy young volunteers who underwent whole body heat stress produced by a hot-water-perfused suit during supine rest for 45 min and 75 degrees head-up tilt (HUT) for 6 min. Esophageal temperature, HR, arterial pressure, and skin blood flow in the forearm and palm were measured continuously throughout the experiment. The sensitivity of the arterial baroreflex control of HR was calculated from the spontaneous changes in beat-to-beat arterial pressure and HR. RESULTS: The HUT was uneventful for 22 volunteers (higher tolerance group), but 22 volunteers (lower tolerance group) reached presyncope after 195 +/- 19 s. Esophageal temperature, HR, arterial pressure, and skin blood flow changed similarly in the two groups during heating. In the preheating condition, the sensitivity of the baroreflex control of HR did not differ significantly between the two groups. Heating did not alter the sensitivity of baroreflex control of HR in the higher tolerance group, but decreased it significantly in the lower tolerance group. Heating increased the number of heartbeats used for analysis of the baroreflex sensitivity in the higher tolerance group, but did not change it in the lower tolerance group. CONCLUSIONS: These results suggest that the impairment of vagal baroreflex control of HR during heat exposure aggravates the orthostatic intolerance in heat-stressed humans.     

21d -6°头低位卧床期间运动训练对骨丢失的防护效应

目的观察21 d -6°头低位卧床运动训练对骨质丢失的防护作用. 方法 10名男性青年志愿者分为卧床对照组和卧床训练组,每组5人,卧床期间训练组每天进行1 h的仰卧位功率自行车训练.分别于卧床前和卧床20 d进行了股骨骨密度(BMD)、血清骨钙素(BGP)、羟脯氨酸/肌酐(HOP/Cr)等指标的测量. 结果与卧床前相比,对照组平均股骨BMD下降了5.8%,而训练组下降0.9%,对照组HOP/Cr不仅显著增加而且也显著高于训练组,BGP两组均降低,但是没有显著性差异. 结论 21 d -6°头低位卧床运动训练对于骨质丢失具有比较明显的防护效应.     

45d-6°头低位卧床对人体运动心肺功能的影响及红景天的防护作用

目的明确45 d-6°头低位卧床(head-down bed rest,HDBR)模拟失重效应对运动心肺功能的影响及红景天的防护作用。方法 16名健康成年男性志愿者,随机分为对照组(8人)和中药组(8人),中药组和对照组在45 d卧床期间,每天分别服用红益胶囊和安慰剂。在卧床实验前、中、后分别进行人体运动心肺功能和运动心电测量。结果与卧床前相比,1)卧床45 d对照组最大耗氧量显著降低(-18.26%;P0.01),中药组最大耗氧量无显著差异(-10.04%;P0.05)。2)对照组最大公斤耗氧量在卧床30 d、45 d和卧床后10 d均较卧床前显著下降(P0.01),而中药组下降均不明显(P0.05)。3)卧床期间对照组和中药组的最大心率均无显著变化,但在卧床后10 d,对照组最大心率明显下降(P0.05),中药组无明显改变(P0.05)。结论 45 d-6°头低位卧床引起人体运动心肺功能明显下降,中药红益胶囊可有效对抗头低位卧床模拟失重效应的人体运动心肺功能下降。