头低位(-20°)限制活动7d对兔庆大霉素药代动力学的影响

目的 探讨模拟失重条件下以血流量改变为生理基础的药代动力学变化。方法 选择庆大霉素作为模型药物,采用头低位（ － ２０°） 兔限制活动为模拟失重动物模型,观察模拟失重对兔庆大霉素药代动力学参数的影响。７ 只家兔在头低位７ ｄ 前后,分别静脉滴注了３ ｍｇ／ｋｇ 的庆大霉素,用 Ｔ Ｄｘ Ｆ Ｌｘ 测定了给药后４ ｈ 内的血药浓度。结果 庆大霉素的分布变慢,这表现在α值由头低位前的（０ ．１８３８ ±０ ．１０７６）ｍｉｎ － １ 降至头低位后的（０ ．０５９１ ±０ ．０３３４） ｍｉｎ － １ ,ｔ１／２α由（５ ．３０ ±３ ．５５） ｍｉｎ 延长为（１５ ．０４ ±７ ．４９）ｍｉｎ , Ｋ１２ 由（０ ．１０２５ ±０ ．０７２１） ｍｉｎ － １ 降至（０ ．０１８１ ±０ ．０１６１） ｍｉｎ１ ,都有显著性差异; Ｖ（ Ｃ） 、 Ｖ（ Ｄ） 也有升高的趋势。庆大霉素清除率在模拟失重后也有所增加, Ｃ Ｌ（ Ｓ） 从（２ ．２ ±０ ．５）ｍｌ·ｍｉｎ１·ｋｇ１ 升至（２ ．７ ±０ ．３）ｍｌ·ｍｉｎ１·ｋｇ１ 。结论 模拟失重可改变药代动力学过程。     

21天头低位-6°卧床对胃电图参数影响的观察

为研究模拟失重因素对胃运动功能的影响，头低位－６°卧床条件下，观察被试者胃电图参数的变化。１５名男性青年自愿被试者平躺于－６°床上，卧床２１ｄ。用便携式胃电图机测定进餐前后的胃电图，并分析功率谱。结果表明，头低位－６°卧床初期，被试者出现不同程度的腹胀、腹痛和食欲差的感觉；卧床后体重显著降低（Ｐ＜０．０１）。在卧床８ｄ以后胃电图胃动过缓（＜２．４ｃｐｍ）的百分数明显增加，胃动过缓节律百分数餐前与餐后有显著差异（Ｐ＜０．０５）；胃动过缓节律的动力学系数显著降低，随卧床时间延长，胃电胃动过缓节律增多，这提示２１ｄ模拟失重因素明显地影响胃运动功能。     

模拟失重状态对扑热臭痛药代动力学的影响

目的　考察人在头低位卧床 (- 6°)模拟失重状态下 ,口服扑热息痛后药代动力学参数的变化 ,以指导载人航天中的合理用药。方法　用人在头低位卧床 (- 6°)模拟航天中的失重状态 ,口服扑热息痛后测定唾液中的药物浓度 ,从而推算血浆中的药物浓度 ,根据血药浓度来计算Cmax、Tmax、AUC(0～ 12h) 。结果　人在头低位卧床 (- 6°)模拟失重状态下 ,Tmax显著延长 ,而Cmax和AUC(0 -12h) 变化不明显 ,直到第 19d才显著降低。结论　头低位卧床 (- 6°)模拟失重状态对口服扑热息痛后的药代动力学参数有明显影响     

头低位－20°限制活动期间兔生理指标的变化

为了用中医药进行失重防护措施的研究，用兔头低位－２０°限制活动的方法作为模似失重的动物模型。将５６只兔放入一个特制的笼内，兔头在外，笼体向下倾斜２０°，实验时间１５ｄ。测量动物在头低位前、中、后体重、血液学指标、溶菌酶、脾淋巴细胞和血脂，比较对照组和头低位组在实验第１５天时的比目鱼肌、腓肠肌、胸腺的重量和心、肺、腹主动脉、肾、比目鱼肌等组织的结构和循环状态。结果发现兔头低位限制活动后，出现了微循环障碍、组织器官结构和功能变化、骨骼肌萎缩、免疫功能下降、血脂增高，这些变化与人和动物在失重时的变化十分相似。因此认为兔头位－２０°限制活动可作为模拟失重的动物模型。实验结果也表明血循环的紊乱是引起其它生理功能紊乱的主要起因。同时发现失重或模拟失重所引起的血循环系统的改变十分类似中医“血瘀症”时的变化，因此提出使用活血化瘀中药来改善失重状态下血循环的看法。     

从IL-2和Bcl-2基因转录水平探讨模拟失重鼠T淋巴细胞功能改变的机制

为探讨模拟失重条件下Ｔ淋巴细胞功能改变的机制，观察了小鼠脾脏Ｔ淋巴细胞增殖能力（ＭＴＴ比色法）、ＩＬ－２产生（生物学测定法）、ＩＬ－２基因（点杂交）和Ｂｃｌ－２癌基因（逆转录ＰＣＲ）转录的变化。结果显示：（１）模拟失重７、１４ｄ小鼠脾脏Ｔ淋巴细胞增殖能力和ＩＬ－２的产生降低，１４ｄ时有显著性（Ｐ＜０．０１）。表明模拟失重降低Ｔ淋巴细胞功能。（２）模拟失重７、１４ｄ小鼠脾脏Ｔ淋巴细胞ＩＬ－２和Ｂｃｌ－２基因转录水平降低，１４ｄ时有显著性（分别为Ｐ＜０．０５和Ｐ＜０．０１）。表明模拟失重通过抑制ＩＬ－２基因转录抑制ＩＬ－２的产生，ＩＬ－２和Ｂｃｌ－２基因对模拟失重引起的Ｔ淋巴细胞功能的降低起一定的作用。     

头低位倾斜条件下运动病易感性的变化

用头低倾斜位（－１０°）模拟失重时的心血管效应，观察和比较了１６名健康青年被试者分别在平卧和头低位两种体位下，平行秋千摆动诱发运动病易感性的差别及头低位１ｈ期间的反应症状；在实验前、中、后测试了心输出量、心率和血压。结果表明，头低位下的秋千运动病易感性比平卧位明显增高（Ｐ＜０．０１）。值得注意的是，在头低位１ｈ期间，有５６％的被试者出现头部不适反应症状，秋千运动病易感性的增高比没有头部不适症状的被试者更为显著。可以认为，在头低位倾斜时的运动病试验可以暴露那些对体液头向转移适应性差，从而影响运动病易感性的人．     

头低位模拟失重状态对前庭功能的影响

为研究头低位模拟失重对运动病症状、垂直视动眼震（ＶＯＫＮ）及体液重新分配的影响，在头低位－１０°的模拟失重状态下，采用大视野的垂直视动刺激，观察１８名正常人的运动病症状、ＶＯＫＮ、激素（ＡＶＰ、ＶＩＰ、ＣＯＲＴ、ＡＬＤＯ）的反应特点。结果表明，头低位－１０°状态下的大视野垂直视动刺激可以诱发出明显的运动病症状，头低位－１０°的垂直视动刺激比坐位更容易诱发运动病。坐位状态ＶＯＫＮ慢相速度有明显的方向性不对称，敏感组ＶＯＫＮ方向性不对称有显著差异（Ｐ＜０．０５）。头低位－１０°时ＶＯＫＮ的不对称现象不明显，向下方向运动的ＶＯＫＮ慢相速度显著增加。分析指出，头低位－１０°状态下垂直视动刺激比坐位和秋千刺激的贡献率大。尿中ＣＯＲＴ（皮质醇）在秋千和头低位的垂直视动刺激前后有显著性增加。提示：大视野的垂直视动刺激与头低位－１０°两种刺激的结合可能成为预测空间运动病的方法之一．     

Effects of Simulated Weightlessness on Erythrocyte Deformability in Rats

为探讨“航天贫血症”的起因，观察了头低位－３０°尾吊组大鼠在实验第７、１５、３０天时的红细胞变形性、膜流动性及细胞形态。结果表明：（１）与对照组相比，尾吊鼠红细胞变形性（ＤＩｍａｘ和ＩＤＩ）在实验第７天已明显降低（Ｐ＜０．０５），第１５天进一步下降（Ｐ＜０．０１），第３０天有所恢复，但仍显著低于对照组（Ｐ＜０．０５）；（２）两组红细胞膜流动性在实验第７天无明显差别，但在第１５天和３０天时，尾吊组的红细胞膜流动性明显降低（Ｐ＜０．０１）；（３）实验期间尾吊鼠血中异形红细胞比例较对照组增加。提示，模拟失重改变了红细胞的流变特性及形态，这可能是导致“航天贫血症”的重要起因之一。     

头低位卧床7d对立位心肺循环功能的影响

目的观察短期模拟失重对立位心肺循环功能的影响,为进一步研究失重时心血管功能下降机理积累资料。方法６名健康男性被试者,头低位６°卧床７ｄ。分别观察卧床前、后立位心肺循环功能的变化。心肺循环功能检测选用ＸＸＨ－２０００型小循环心功能检测仪。结果头低位卧床７ｄ致被试者立位耐力降低,卧床后右心室射血期（ｊ－ｚ）缩短,右心室排血效率降低（Ｑ－ｊ／ｊ－ｚ升高）,提示右心功能减退。心血管调节适应性反应减弱,右心功能储备降低。结论ｃ波高度（ｈｃ）、ｃ波高度与Ｚ波高度的比值（ｈｃ／ｈｚ）可作为评价立位耐力或预测立位晕厥的指标;小循环心功能检测法评价立位心肺循环功能的变化有一定的前景。     

卧床模拟失重对人体急性缺氧耐力的影响

为探讨卧床模拟失重对机体缺氧耐力的影响，对６名受试者，头低位４°卧床（－４°ＨＤＢＲ）７ｄ，检查了卧床前后缺氧耐力和立位耐力，记录了ＥＣＧ、ＢＰ及ＨＲ的变化。结果表明：－４°ＨＤＢＲ模拟失重降低了机体的缺氧耐力；缺氧耐力与心血管失调间有很好的相关性。     

Aerobic fitness: II. Orthostasis and VO2peak following head-down tilt.

To determine whether endurance exercise trained (ET) subjects would experience greater reductions in peak oxygen delivery and orthostatic tolerance (OT) than untrained (UT) subjects, both peak oxygen uptake (VO2peak) during upright bicycle ergometry and tolerance time during 70 degrees head-up tilt (HUT) were compared within and between groups before and after 4 h of -6 degrees head-down tilt (HDT). Eight ET subjects with a mean VO2peak of 61.7 +/- 1.6 ml.kg-1.min-1 were matched for age, height, and weight with eight UT subjects (VO2peak = 38.4 +/- 1.7 ml.kg-1.min-1). Following HDT, decreases in plasma volume (PV) were larger for ET subjects (-3.7 +/- 0.5 ml.kg-1) than for UT subjects (-2.3 +/- 0.3 ml.kg-1), P less than 0.03. Reductions in VO2peak for ET subjects (-5.4 +/- 1.1 ml.kg-1.min-1) were also greater than for UT subjects (-2.4 +/- 0.8 ml.kg-1.min-1), P less than 0.05. The ET (N = 6) subjects also had a significant decrease in OT time (-13.0 +/- 4.2 min) during post-HDT HUT, which was not observed for the UT group (N = 6). A significant inverse correlation was found pre-HDT VO2peak and the change in OT time, r = -0.74, P less than 0.01. The decrease in OT was also significantly correlated to the PV decrease, r = 0.59, P less than 0.04. The UT subjects had significantly augmented pressor responses to HUT manifested by the increases in both HR and MAP following HDT.(ABSTRACT TRUNCATED AT 250 WORDS)     

Aerobic fitness: I. Response of volume regulating hormones to head-down tilt.

We investigated the relationship of aerobic fitness to the response of volume-regulating hormones to acute simulated microgravity. Six untrained (UT) and six endurance-trained (ET) healthy young males were studied in the head-down tilt (HDT) position of -6 degrees for 4 h. Peak oxygen uptake (VO2peak) and plasma volume (PV) were significantly greater in the ET (VO2peak = 61.7 +/- 1.6 ml.min-1.kg-1 and PV = 53.1 +/- 2.8 ml.kg-1) than in the UT (VO2peak = 38.4 +/- 1.7 ml.min-1.kg-1 and PV = 38.8 +/- 1.0 ml.kg-1). Plasma concentrations of atrial natriuretic peptide (ANP), arginine vasopressin (AVP), norepinephrine (NE), renin activity (PRA), and aldosterone (PA) were measured prior to HDT and at minutes 2, 5, 15, 30, 60, 120, 180, and 240 during HDT. PRA and PA significantly decreased during the time of HDT in both groups. The changes in ANP and NE concentrations were not significantly different between the groups nor across time. However, in the ET subjects, the changes in PRA and NE were significantly correlated with the changes in ANP (r = 0.49, P less than 0.01; and r = 0.86, P less than 0.001, respectively); in the UT subjects, the changes in AVP, PRA, and PA were significantly associated with changes in NE (r = 0.34, P less than 0.03; and r = 0.59; and r = 0.53, P less than 0.01, respectively). PV significantly decreased during HDT, and was primarily related to the decrease in PA in both groups.(ABSTRACT TRUNCATED AT 250 WORDS)     

模拟失重对新西兰兔股静脉压力-容积关系的影响

目的观察模拟失重对兔股静脉压力 -容积关系的影响及静脉壁显微结构的变化。方法采用头低位 ( - 2 0°)倾斜的方法作为模拟失重家兔模型。 2 4只雄性健康新西兰兔 ,随机分为对照组、模拟失重 2 1d组和模拟失重 1 0d组 ,每组 8只。进行股静脉的压力 -容积 (P V)关系测试 ,并观察血管壁的显微结构。结果模拟失重后股静脉P V曲线向容积变化比增大的方向移动 ,模拟失重 2 1d组较 1 0d组移动更明显。分别于加、卸载测试时拟合出的模拟失重 2 1d组P V二次抛物线方程式系数B1 、B2 值均显著高于对照组及模拟失重 1 0d组 (P <0 .0 1 ) ,模拟失重 1 0d组的B1、B2值和对照组相比有增加的趋势。组织学观察表明 ,模拟失重组股静脉内皮细胞呈立方或矮柱状并有细胞脱落 ,平滑肌层变薄等变化。结论模拟失重后股静脉顺应性增加 ,2 1d组较 1 0d组增加明显 ,同时股静脉管壁结构也发生明显改变     

Diminished baroreflex control of forearm vascular resistance following training.

The stimulus-response characteristics of cardiopulmonary baroreflex control of forearm vascular resistance (FVR units in mm Hg.min.100 ml.ml-1) were studied in 14 volunteers before and after 10 wk of endurance training. We assessed the relationship between reflex stimulus (changes in central venous pressure, CVP) and response (FVR) during unloading of cardiopulmonary baroreceptors with lower body negative pressure (LBNP, 0 to -20 mm Hg). Changes in CVP during LBNP were estimated from pressure changes in a large peripheral vein in the dependent arm of the subject in the right lateral decubitus position. Maximal oxygen uptake (VO2max) and total blood volume increased with endurance training from 37.8 +/- 1.4 ml.min-1.kg-1 and 63.6 +/- 2.1 ml.kg-1 to 45.3 +/- 1.4 ml.min-1.kg-1 and 69.3 +/- 2.8 ml.kg-1, respectively (P less than 0.05). Reflex forearm vasoconstriction occurred in response to a reduction in estimated CVP, and the absolute change in FVR per unit of CVP was reduced from -5.96 +/- 0.79 to -4.06 +/- 0.52 units.mm Hg-1 (P less than 0.05) following exercise training but was unchanged from -6.10 to 0.57 to -6.22 +/- 0.94 units.mm Hg-1 for the time control group (N = 7). Resting values for FVR were similar before and after exercise training; however, resting estimated CVP was elevated from 9.5 +/- 0.5 mm Hg before training to 11.3 +/- 0.6 mm Hg after training.(ABSTRACT TRUNCATED AT 250 WORDS)     

Heart rate and estimated energy expenditure during ballroom dancing.

Ten competitive ballroom dance couples performed simulated competitive sequences of Modern and Latin American dance. Heart rate was telemetered during the dance sequences and related to direct measures of oxygen uptake and heart rate obtained while walking on a treadmill. Linear regression was employed to estimate gross and net energy expenditures of the dance sequences. A multivariate analysis of variance with repeated measures on the dance factor was applied to the data to test for interaction and main effects on the sex and dance factors. Overall mean heart rate values for the Modern dance sequence were 170 beats.min-1 and 173 beats.min-1 for males and females respectively. During the Latin American sequence mean overall heart rate for males was 168 beats.min-1 and 177 beats.min-1 for females. Predicted mean gross values of oxygen consumption for the males were 42.8 +/- 5.7 ml.kg-1 min-1 and 42.8 +/- 6.9 ml.kg-1 min-1 for the Modern and Latin American sequences respectively. Corresponding gross estimates of oxygen consumption for the females were 34.7 +/- 3.8 ml.kg-1 min-1 and 36.1 +/- 4.1 ml.kg-1 min-1. Males were estimated to expand 54.1 +/- 8.1 kJ.min-1 of energy during the Modern sequence and 54.0 +/- 9.6 kJ.min-1 during the Latin American sequence, while predicted energy expenditure for females was 34.7 +/- 3.8 kJ.min-1 and 36.1 +/- 4.1 kJ.min-1 for Modern and Latin American dance respectively. The results suggested that both males and females were dancing at greater than 80% of their maximum oxygen consumption. A significant difference between males and females was observed for predicted gross and net values of oxygen consumption (in L.min-1 and ml.kg-1 min-1).     

Dissociation of the ventilatory and lactate thresholds following caffeine ingestion

Caffeine ingestion prior to the start of exercise has been shown to have an effect on ventilatory parameters and substrate utilization. Changes in either substrate utilization or ventilatory parameters may influence the determination of the lactate threshold (LT) and/or the ventilatory threshold (VT). Therefore, it was the purpose of this investigation to determine whether the VT and LT occur at similar metabolic rates and what effect caffeine ingestion will have on these two measures. Ten male subjects completed two maximal exercise bouts on the treadmill using a single blind procedure. One trial was performed 45 min after the ingestion of caffeine citrate (CC) in an amount equal to 7.0 mg of anhydrous caffeine.kg-1 body weight. The second trial was performed 45 min after the ingestion of a gelatin powdered placebo (P). Ventilatory parameters were monitored on a breath-by-breath basis, and blood for lactate determination was obtained from an antecubital vein every minute. Maximal oxygen consumption did not differ significantly between the CC (60.3 +/- 5.2 ml.kg-1.min-1) and P (59.7 +/- 5.6 ml.kg-1.min-1) trials. Oxygen consumption (VO2) values during the P trial at the VT (40.2 +/- 6.1 ml.kg-1.min-1) and the LT (38.6 +/- 3.3 ml.kg-1.min-1) were not significantly different (P less than 0.05). During the CC trial, VO2 values at the VT (44.4 +/- 6.6 ml.kg-1.min-1) and the LT (39.7 +/- 5.8 ml.kg-1.min-1) were significantly different. When comparing the VO2 at the LTs between the CC and P trials, there was no significant difference. There was, however, a significant difference in VO2 at the VTs when comparing the two trials. These data demonstrate a dissociation between the VT and LT following caffeine ingestion and suggest that the use of the VT as an indicator of the LT may be inappropriate following ingestion of moderate dosages of caffeine.     

Aerobic and anaerobic power characteristics of Saudi elite soccer players

BACKGROUND: To assess the aerobic and anaerobic characteristics of Saudi elite soccer players, and to examine the interrelationship between measures of aerobic and anaerobic power in the elite soccer players. METHODS. PARTICIPANT: Twenty-three outfield elite soccer players representing the Saudi national team participated. Their means (+/- SD) for age, body mass, height and estimated fat % were: 25.2 +/- 2.3 years; 73.1 +/- 6.8 kg; 177.2 +/- 5.9 cm; and 12.3 +/- 2.7%, respectively. MEASURES: Cardiorespiratory parameters, including maximal oxygen uptake (V O2 max), were assessed by open-circuit spirometry during graded treadmill running. Anaerobic power measures were obtained using Wingate anaerobic test, and included peak power (PP), and average power for 5 sec (AP 5), 10 sec (AP 10), 20 sec (AP 20) and 30 sec (AP 30). RESULTS: Mean (+/-SD) values for V O2max in absolute and relative to body mass were 4.16 +/- 0.34 l x min-1 and 56.8 +/- 4.8 ml x kg-1 x min-1, respectively. Such V O2max value was 118% and 80% of those reported for Saudi college males and distance runners, respectively. The ventilatory anaerobic thereshold (Tvent) averaged 43.6 ml x kg-1 x min-1. There were no significant differences in V O2max and Tvent between players based on positions, although the midfielders and the centre-backs had the highest and the lowest individual values for both measures, respectively. Values (+/- SD) of PP and AP 30 were 873.6 +/- 141.8 W (11.88 +/- 1.3 W x kg-1), and 587.7 +/-55.4 W (8.02 +/- 0.53 W x kg-1), respectively. Only in absolute PP & AP 30 were the centre-backs significantly superior to the other players. In addition, V O2max was inversely related to PP (r = - 0.54; p < 0.05) and positively related to AP 30 (r = 0.45; p < 0.05). CONCLUSIONS: The aerobic power, expressed relative to body mass, of Saudi elite soccer players was in the lower range of values normally reported in the literatures for elite soccer players. Both PP and AP 30 were somewhat lower than values previously reported for elite soccer players from other countries.     

Elite special forces: physiological description and ergogenic influence of blood reinfusion

We measured the physical exercise capabilities of U.S. Army Special Forces soldiers (male) and determined the subsequent ergogenic influence of autologous blood reinfusion. Twelve subjects (Ss) completed maximal exercise treadmill testing in a comfortable (Ta = 20 degrees C, Tdp = 9 degrees C) environment. Six Ss were later transfused with a 600 ml autologous red blood cell (50% Hct) NaCl glucose-phosphate solution and completed identical maximal exercise tests 3 and 10 d posttransfusion. Pretransfusion, the 12 Ss had a maximal oxygen uptake (VO2max) of 4.36 +/- 0.56 L . min-1 and 55 +/- 4 ml . kg-1 . min-1 with a heart rate of 188 +/- 10 b . min-1 and ventilatory equivalent for oxygen of 37 +/- 3. For the 6 reinfused Ss, hemoglobin and red cell volume (RCV) increased by 10% (p less than 0.05) and 11% (p less than 0.05), respectively, posttransfusion. Reinfusion increased (p less than 0.05) VO2max from 4.28 +/- 0.22 L . min-1 (54 +/- 5 ml . kg-1 . min-1) to 4.75 +/- 0.42 L . min-1 (60 +/- 6 ml . kg-1 . min-1) and 4.63 +/- 0.21 L . min-1 (59 +/- 6 ml . kg-1 . min-1) at 3 and 10 d posttransfusion, respectively. No significant relationship was found between the individual change in RCV and VO2max values pre- to posttransfusion. We conclude that Special Forces soldiers have high levels of aerobic fitness that can be further increased by blood reinfusion for at least 10 d.     

中药复方对模拟失重兔血流变特性及循环系统的调节作用

目的研究中药复方对模拟失重兔血流变及循环系统的调节作用,为防护失重对心血管功能的不良影响提供依据。方法用兔头低位(-20°)倾斜9d模拟失重,观察中药复方对兔血液流变学、血脂指标及立位耐力的影响。结果兔模拟失重后红细胞压积减少,红细胞变形能力明显下降,纤维蛋白原含量有增加趋势;胆固醇和低密度脂蛋白明显增加,甘油三脂有轻度增高趋势。中药复方对血液流变学指标改善不明显,但有降低甘油三脂的趋势,对胆固醇的增加也有抑制的趋势。在负压-立位实验过程中,对照组兔模拟失重后立位耐受时间减少,中止实验前出现了ST段下移、T波倒置及心律紊乱等明显的心肌缺血性改变;而中药组兔心率平稳,心电图缺血性改变不明显,立位耐受时间增加。结论中药复方对模拟失重兔的立位耐力降低具有显著的防护作用,同时还能改善血脂代谢,从整体上对机体各系统进行调节,提高了机体适应外界不良环境、抵御不良刺激的能力。     

Effect of longitudinal physical training and water immersion on orthostatic tolerance in men

To test the hypothesis that moderately intense physical training has no effect on orthostasis, orthostatic and fluid-electrolyte-endocrine responses to 60 degrees head-up tilt were compared before and after 6 h of water immersion (34.5 +/- 0.1 degrees C) up to the neck following 6 months of exercise training. During the tilt test the five male subjects (27-42 years) each wore a lower-body positive-pressure suit (MAST-111A antishock trousers). The tilt procedure consisted of a 40-min supine control period (suit deflated), followed by a maximum 90-min tilt period (suit inflated to 50 +/- 5 mm Hg for 30 min, then deflated for 60 min or until presyncope). The mean +/- S.E. pretraining cycle ergometer peak VO2 was 3.20 +/- 0.14 L.min-1 (39 +/- 2 ml.min-1.kg-1), 3.36 +/- 0.27 L.min-1 (42 +/- 4 ml.min-1.kg-1) after 3 months (N.S.), and increased by 18% to 3.78 +/- 0.36 L.min-1 (48 +/- 5 ml.min-1.kg-1, +22%, p less than 0.05) posttraining. During pretraining, water immersion tilt tolerance decreased from 74 +/- 16 min before to 34 +/- 9 min (delta = 40 min, p less than 0.05) after immersion. During posttraining, water immersion tilt tolerance decreased similarly from 74 +/- 16 min preimmersion to 44 +/- 13 min (delta = 30 min, p less than 0.05) postimmersion (74 vs. 74 min, N.S.; 34 vs. 44 min, N.S.).(ABSTRACT TRUNCATED AT 250 WORDS)