高原地区老年慢性肺心病夜间睡眠减氧饱和的研究

目的：探讨高原老年肺心病夜间睡眠减氧饱和及与呼吸功能的关系。方法：对３４例高原老年肺心病缓解期患者作了白天觉醒时的血气、１秒钟用力呼气容积（ＦＥＶ１）、７５％、５０％和２５％肺活量大呼气流量［Ｖ７５／Ｈｔ（ｍ）、Ｖ５０／Ｈｔ（ｍ）、Ｖ２５／Ｈｔ（ｍ）］、最大跨膈压（Ｐｄｉｍａｘ）和夜间睡眠时的脑电图、眼动图、血氧饱和度（ＳａＯ２）连续监测。结果：高原老年肺心病患者夜间睡眠时快动眼睡眠（ＲＥＭ）和非ＲＥＭ（ＮＲＥＭ）期平均（ＭＳａＯ２）和最低ＳａＯ２（ＭｍＳａＯ２）较白天觉醒ＳａＯ２（ＤＳａＯ２）明显降低，均为Ｐ＜０．０１，以ＲＥＭ期最明显，高碳酸血症组较正常碳酸血症组降低明显（Ｐ＜０．０１或０．０５）。ＭＳａＯ２与ＤＳａＯ２、ＦＥＶ１、Ｖ７５／Ｈｔ（ｍ）、Ｖ５０／Ｈｔ（ｍ）、Ｖ２５／Ｈｔ（ｍ）Ｐｄｉｍａｘ和ＭｍＳａＯ２与ＤＳａＯ２呈明显正相关，ｒ＝０．７３８、０．６８７、０．７７１、０．８８９、０．５６８、０．８７６、０．８２２，均为Ｐ＜０．０１。结论：高原老年肺心病患者夜间睡眠有明显减氧饱和，尤以ＲＥＭ期最明显，且与肺和肺膈肌功能损害程度正相关。     

高原红细胞增多症与摄氧能力及运动能力的研究

目的：探讨高原红细胞增多症（ＨＡＰＣ）与摄氧能力及运动能力的关系；方法：在海拔３４１７ｍ和４２８０ｍ地区对１８例ＨＡＰＣ的心功能、最大摄氧量（ＶＯ２ｍａｘ）、最大运动能力和最大心排出量（ＣＯｍａｘ）进行了检测；结果：红细胞压积（Ｈｃｔ）与每搏量（ＳＶ）呈显著负相关、ＨＡＰＣ的ＶＯ２ｍａｘ、ＣＯｍａｘ和最大运动能力都明显低于对照组，同时ＳａＯ２明显下降；结论：ＨＡＰＣ的心排出量下降引起供氧能力下降和     

急性运动对血清超氧化物歧化酶的影响及其与有氧能力的关系

为了探讨急性运动对血清Ｔ－ＳＯＤ、Ｍｎ－ＳＯＤ及ＣｕＺｎ－ＳＯＤ活性的影响及它们与有氧能力的关系，让１４名青少年运动员在功率自行车上以逐级递增负荷的方式运动至力竭，测定了他们的ＶＯ２ｍａｘ及运动前后的血清Ｔ－ＳＯＤ、Ｍｎ－ＳＯＤ和ＣｕＺｎ－ＳＯＤ。结果发现：①急性运动可导致血清Ｔ－ＳＯＤ、Ｍｎ－ＳＯＤ活力发生非常显著的升高（Ｐ＜０．０１）。运动后血清ＣｕＺｎ－ＳＯＤ活性也有明显增加（Ｐ＜０．０５）。急性运动时血清ＳＯＤ活性增加可能是机体抗自由基损伤及延缓疲劳出现的一个防御机制。②血清Ｔ－ＳＯＤ、Ｍｎ－ＳＯＤ与ＶＯ２ｍａｘ之间存在着非常显著的正相关（Ｐ＜０．０ｌ）。ＣｕＺｎ－ＳＯＤ与ＶＯ２ｍａｘ之间也具有明显的相关性（Ｐ＜０．０５）。血清ＳＯＤ活性与有氧能力之间的密切关系，可能有利于更好地清除线粒体在有氧代谢过程中产生的氧自由基。     

COPD患者流速容量环及其与运动能力的关系

目的：探讨慢性阻塞性肺疾病（ＣＯＰＤ）患者呼吸运动方式和运动受限的原因。方法：ＣＯＰＤ患者在功率自行车上运动至最大运动量,观察其潮气流速容量环的变化特点,并利用相关和逐步回归分析判断运动中最大公斤耗氧量（ＶＯ２ｍａｘ／ｋｇ）与静态最大流速容量环呼气流速间的关系。结果：１ＣＯＰＤ患者运动中潮气流速容量环的变化有其特点;２ＣＯＰＤ患者最大公斤耗氧量与Ｖ７５％、Ｖ５０％和Ｖ２５％呈显著正相关（ｒ分别为０．８５７,０．８７５和０．７８９,Ｐ＜０．０１）;３ＣＯＰＤ患者ＶＯ２ｍａｘ／ｋｇ与Ｖ５０％存在直线回归关系ｔ＝６．３７３,Ｐ＜０．０１。结论：１ＣＯＰＤ患者的特殊呼吸方式为运动中潮气流速容量环逐渐向肺总量位附近偏移;２静态Ｖ５０％减小是ＣＯＰＤ患者运动受限的主要原因。     

不同海拔高度健康人超氧化物歧化酶和丙二醛的测定

对不同海拔高反的西安市（海拔３４０ｍ）、西宁市（２２６０ｍ）、茶卡镇（３１００ｍ）和甘德地区（４０８０ｍ）共１０８９例健康人进行了红细胞——超氧化物歧化酶（ＳＯＤ）和血清丙二醛（ＭＤＡ）测定。结果表明：随着海拔高度的升高和大气压、大气氧分压的降低，血清ＭＤＡ明显增加（Ｐ＜０．０１），红细胞ＳＯＤ显著降低（Ｐ＜０．０１）。相关分析表明：ＭＤＡ与大气氧分压呈明显负相关（ｒ＝－０．９７９，Ｐ＜０．０５），ＳＯＤ与大气氧分压呈明显正相关（ｒ＝０．９８４，Ｐ＜０．０５）。本文对长期生活在高原低氧环境下居民ＭＤＡ升高和ＳＯＤ降低的原因进行了探讨。     

西宁地区严重创伤患者并发成人呼吸窘迫综合征氧动力学变化

目的 探讨西宁地区严重创伤后并发成人呼吸窘迫综合征（ＡＲＤＳ）时氧动力学变化,为治疗提供理论依据。方法 利用Ｓｗａｎ－ Ｇａｎｚ导管及热稀释法心输出量测定技术对２０例ＡＲＤＳ患者进行监测。结果 （保）监测开始１～２ｄ存活组和死亡组的氧输送（ＤＯ２）逐渐上升,氧耗量（ＶＯ２）也随之上升,出现病理性氧供依赖（ｒ＝０．６１７６,Ｐ〈０．０５）,两组间比较无显著性差异。（２）抢救４－５ｄ以后,存活组患者Ｄ     

部队在高原越野前后RBC—SOD和血液流变学的变化

探讨海拔５０００ｍ以上地区剧烈运动前后ＲＢＣ──ＳＯＤ活性和血液流变性的变化。５１名平原青年在海拔３７００和５２７０ｍ处进行５公里跑步越野，越野前静息状态和越野后即刻检测ＲＢＣ－ＳＯＤ和６项血液流变学指标。ｔ检验分组比较，结果：静息状态随海拔升高ＲＢＣ－ＳＯＤ活性逐步下降，５２７０ｍ较３７００ｍ下降非常显著（Ｐ＜０．０１），ＨＣＴ和ηｂ逐步增高，亦相差非常显著（Ｐ＜０．０１），ＰＦＣ无显著改变。ＴＫ在３７００ｍ较１４００ｍ增加非常显著（Ｐ＜０．０１），５２７０ｍ较３７００ｍ虽有增加但无统计学意义。ＴＦＬ随海拔升高增加非常显著或增加显著（Ｐ＜０．０１或Ｐ＜０．０５），ＭＳＴ虽有增加但无显著性差异（Ｐ＞０．０５）。越野后即刻较越野前，海拔３７００ｍＲＢＣ－ＳＯＤ、ηｂ、ＴＦＬ显著降低（Ｐ＜０．０５），ＭＳＴ降低非常显著（Ｐ＜０．０１）。海拔５２７０ｍＲＢＣ－ＳＯＤ和ηｂ降低非常显著（Ｐ＜０．０１），其它指标无显著性改变。结论：随海拔升高ＲＢＣ－ＳＯＤ活性降低，血液粘度增高；剧烈运动后ＲＢＣ－ＳＯＤ进一步降低，血液粘度相对降低。     

高原移居和世居者低,高氧通气的反应变化

目的探讨高原移居者和世居者对低氧和高氧的通气反应性。方法对５名从平原移居海拔４７５０ｍ２０天～８０天的汉族（Ⅰ组）、１６名从平原移居该高原３年～２０年的汉族（Ⅱ组）和５名当地世居藏族（Ⅲ组）受试者做了呼吸空气、进行性低氧和１００％氧的通气反应测定，以ＶＥ／Ｓａ０２（Ｌｍｉｎ－１）表示通气反应大小。结果呼吸空气时，Ⅰ组ＶＥ／Ｓａ０２值（０．１８±０．１４）明显高于Ⅱ组（０．１３±０．０３）和Ⅲ组（０．１３±０．０３），Ｐ＜０．０５，Ⅱ、Ⅲ组间无显著性差异。进行性低氧１ｍｉｎ、２ｍｉｎ和３ｍｉｎ，Ⅰ组ＶＥ／Ｓａ０２值（分别为０．２０±０．０４、０．２７±０．０４和０．５６±０．０７）明显高于Ⅱ组（０．１４±０．０４、０．２０±０．０４和０．３４±０．０５）和Ⅲ组（０．１３±０．０２、０．１５±０．０３和０．２２±０．０４），Ｐ＜０．０５，Ⅱ、Ⅲ组间第１ｍｉｎ和第２ｍｉｎ无显著性差异，第３ｍｉｎ有显著性差异（Ｐ＜０．０５）。三组吸入１００％氧时，通气量均明显降低。结论平原人移居高原初期，低氧通气反应敏感，而久居和世居高原者则迟钝。三组吸高氧时，通气均被抑制。     

高压氧间断暴露及氧惊厥对大鼠抗氧化酶活力及脂质过氧化物含量的影响

目的：为研究高压氧暴露对机体抗氧化酶系统的影响，本实验观察了高比氧间断暴露及氧惊厥条件下，大鼠红细胞、肺和肝组织中抗氧化酶（ＳＯＤ、ＧＳＨｐｘ、ＣＡＴ）活力及作为脂质过氧化物（ＬＰＯ）指标的丙二醛（ＭＤＡ）的含量的变化。方法：３８只雄性ＳＤ大鼠随机分组为：常压空气对照组（ｎ＝１２）；０．３ＭＰａＮ＿２－Ｏ＿２（ＰＯ＿２＝２１ｋＰａ）组（ｎ＝６）与０．３ＭＰａＯ＿２组（ｎ＝１２），暴露时间均为每天３０分钟，连续１０天；氧惊厥组（ｎ＝８）为０．６ＭＰａＯ＿２暴露１５分钟１次。结果：０．３ＭＰａＯ＿２，及０．３ＭＰａＮ＿２０Ｏ＿２两组组织中ＳＯＤ、ＧＳＨｐｘ、ＣＡＴ的活力及ＭＤＡ含量没有显著变化；０．６ＭＰａＯ＿２氧惊厥组，红细胞中ＧＳＨｐｘ活力与对照相比显著下降（Ｐ＜０．０５），而红细胞及肝组织中的ＭＤＡ含量则显著升高（Ｐ＜０．０５），但ＳＯＤ及ＣＡＴ活力无明显变化。结论：本实验中高压氧间断暴露方式对机体没有明显损害作用；氧中毒时ＧＳＨｐｘ活力易受抑制为抗氧化酶防御系统中的薄弱环节。     

加强营养支持对改善高原地区肺心病营养不良患者呼吸和免疫功能的作用

目的：为探讨加强营养支持对高原地区肺心病缓解期营养不良患者呼吸和免疫功能的作用；方法：对３０例高原（海拔２２６０～３２００ｍ）慢性肺心病缓解期营养不良（ＮＤ）患者在加强营养支持前后作了肺功能、吸气肌功能、动脉血气、血清免疫球蛋白和补体测定，并与本地肺心病营养正常（ＮＮ）患者对比；结果：ＮＤ组三头肌皮肤皱褶厚度（ＴＳＦ）、上臂中部周径（ＭＡＭＣ）、口腔最大吸气压（ＰＩｍａｘ）、最大跨膈压（Ｐｄｉｍａｘ）、ＰａＯ２、ＩｇＡ、Ｃ３、Ｃ４均明显低于ＮＮ组（Ｐ均＜０．０１），膈肌张力—时间指数（ＴＴｄｉ）和ＰａＣＯ２明显高于ＮＮ组（Ｐ均＜０．０１），两组ＦＥＶ１．０、ＩｇＧ、ＩｇＭ无差异性。ＮＤ组加强营养支持６周后，体重明显增加，ＴＳＦ、ＭＡＭＣ、ＰＩｍａｘ、Ｐｄｉｍａｘ、ＰａＯ２、ＩｇＡ、Ｃ３、Ｃ４明显提高（Ｐ＜０．０１或＜０．０５），ＴＴｄｉ，ＰａＣＯ２明显下降（Ｐ＜０．０１）；结论：加强营养支持治疗能明显改善高原地区肺心病营养不良患者的呼吸功能和增强其免疫功能。     

Chronic mountain sickness: recent studies of the relationship between hemoglobin concentration and oxygen transport

Although an increase in hemoglobin concentration [Hb] in high altitude residents assists oxygen transport, excessive polycythemia ([Hb] > or = 21 g/100 mL) may cause the syndrome of chronic mountain sickness (CMS). A recent theoretical analysis has suggested that increasing [Hb] above 18 g/100 mL provides no further benefit in oxygen transport at rest. To test this hypothesis, we examined oxygen transport at rest for given arterial oxygen saturations (Sa(O2), in classes at intervals of 5%) as reported in 206 residents of various altitudes. For Sa(O2) of 97% versus 87%, [Hb] and a-v oxygen content difference increased (respectively, 14.5 to 17.5 g/100 mL and 4.11 to 5.03 volume %). As Sa(O2) fell further to 66%, a-v progressively decreased to 3.77 volume %, despite an increase in [Hb] to 24.2 g/100 mL. Over the Sa(O2) range of 97% to 66%, the a-v difference changed little (-8%) compared to other subjects made acutely hypoxic (-33%), for Sa(O2) change from 97% to 75%. The results suggest that increasing [Hb] allows greater oxygen extraction (a cardiac output sparing effect), which is maximal at Sa(O2) of 87% and a [Hb] of 17.5 g/100 mL. For more severe hypoxemia, even to Sa(O2) of 66%, both increasing [Hb] and increasing output are utilized for oxygen transport.     

Absolute and relative work capacity in women at 758, 586, and 523 torr barometric pressure

Six young women performed an incremental bicycle work test at sea level barometric pressure (PB = 758 torr) and during acute exposure (1 h) to simulated altitudes of PB 586 and 523 torr. Submaximal oxygen uptake (VO2) for a given workload was independent of altitude but maximal oxygen uptake (VO2 max) decreased 10 and 13%, respectively, at the higher altitudes. Although heart rate (fC) was consistently higher at altitude for a given VO2, the slope of fC vs, VO2 was independent of altitude and VO2 max. Exercise fC appeared to be a function of the relative workload i.e. VO2 as a percentage of VO2 max measured at each PB. Carbon dioxide (CO2) elimination increased with altitude for a given VO2 but also was a function of the relative workload. Pulmonary ventilation (BTPS), however, was consistently 10-15% higher at altitude when expressed as a percent of VO2 max, primarily due to an increase in respiratory rate. Compared to published studies on males, this increased ventilation may impart a slight advantage to women in maintaining arterial oxygenation, but ventilatory reserve may be decreased and limited at higher altitudes. At altitudes down to PB 523 torr, the control of fC responses and decrements in maximal oxygen uptake in women were similar to males, but ventilatory control mechanisms differed.     

Effect of acute hypoxia on maximal exercise in trained and sedentary women

PURPOSE: The purpose of this study was to determine the physiological responses of sedentary and endurance-trained female subjects during maximal exercise at different levels of acute hypoxia. METHODS: Fourteen women who were sea level residents were divided into two groups according to their level of fitness: 1) endurance-trained women (TW) (N = 7), VO(2max) = 56.3 +/- 4.7 mL.kg(-1).min(-1); and 2) sedentary women (SW) (N = 7), VO(2max) = 34.8 +/- 5.6 mL.kg(-1).min(-1). Subjects performed four maximal cycle ergometer tests in normoxia and under hypoxic conditions (F(I)O(2) = 0.187, 0.154, and 0.117, corresponding to altitudes of 1000, 2500, and 4500 m, respectively). RESULTS: VO(2max) decreased significantly by 3.6 +/- 2.1, 14 +/- 2.5, and 27.4 +/- 3.6% in TW, and by 5 +/- 4, 9.4 +/- 6.4, and 18.7 +/- 7% in SW at 1000, 2500, and 4500 m, respectively. The drop of VO(2max) (DeltaVO(2max)) was greater in TW at and above 2500 m. Arterial O2 saturation (SpO(2)) at maximal exercise was lower in TW at every altitude (1000 m: 90.9 +/- 1.9 vs 94.6 +/- 1.4%; 2500 m: 82.8 +/- 2.8 vs 90.0 +/- 2.1%; 4500 m: 65.0 +/- 4.7 vs 73.6 +/- 4.5%). Maximal heart rate decreased significantly from 1000 m in the two groups. SpO(2) was correlated to DeltaVO(2max) at 4500 m (r = -0.81, P < 0.01) and 2500 m (r = -0.81, P < 0.01), but not below. Furthermore, we noted a relationship between SpO(2) and O2 pulse (VO(2)/HR) at every F(I)O(2). CONCLUSION: These results demonstrate that endurance-trained women show a greater decrement in VO(2max) at high altitudes. This could be explained mainly by a higher arterial desaturation, which is largely caused, according to our results, by diffusion limitation.     

Role of maximal heart rate and arterial O2 saturation on the decrement of VO2max in moderate acute hypoxia in trained and untrained men

We aimed to evaluate 1) the altitude where maximal heart rate (HR (max)) decreases significantly in both trained and untrained subjects in moderate acute hypoxia, and 2) if the HR (max) decrease could partly explain the drop of V.O (2max). Seventeen healthy males, nine trained endurance athletes (TS) and eight untrained individuals (US) were studied. Subjects performed incremental exercise tests at sea level and at 5 simulated altitudes (1000, 1500, 2500, 3500, 4500 meters). Power output (PO), heart rate (HR), arterial oxygen saturation (SaO (2)), oxygen uptake (V.O (2)), arterialized blood pH and lactate were measured. Both groups showed a progressive reduction in V.O (2max). The decrement in HR (max) (DeltaHR (max)) was significant from 1000 m for TS and 2500 m for US and more important in TS than US (at 1500 m and 3500 m). At maximal exercise, TS had a greater reduction in SaO (2) (DeltaSaO (2)) at each altitude. DeltaHR (max) observed in TS was correlated with DeltaSaO (2). When the two groups were pooled, simple regressions showed that DeltaV.O (2max) was correlated with both DeltaSaO (2) and DeltaHR (max). However, a multiple regression analysis demonstrated that DeltaSaO (2) alone may account for DeltaV.O (2max). Furthermore, in spite of a greater reduction in SaO (2) and HR (max) in TS, no difference was evidenced in relative DeltaV.O (2max) between groups. Thus, in moderate acute hypoxia, the reduction in SaO (2) is the primary factor to explain the drop of V.O (2max) in trained and untrained subjects.     

平原人进驻高原后红细胞生成素的变化

目的　探讨红细胞生成素在高原低氧适应机制中的作用。方法　对平原进驻海拔 3 70 0m和气 5 3 80m第 7天及半年的健康青年进行血液促红细胞生成素 (EPO)、血红蛋白 (Hb)及血氧饱和度 (SaO2 )检测 ,并与平原健康青年作对照。结果　进驻高原低氧环境EPO、Hb较平原增高显著 (P <0 .0 5或 0 .0 1 ) ,SaO2 降低非常显著 (P <0 .0 1 )。进驻高原第 7天和半年 ,3 70 0m较 5 3 80mEPO ,Hb降低非常显著 ,SaO2 增高非常显著 (P <0 .0 1 )。进驻 3 70 0m ,第 7天较半年EPO无统计学意义 (P >0 .0 5 ) ,Hb ,SaO2 差异显著 (P <0 .0 5或 0 .0 1 ) ;进驻 5 3 80m ,第 7天较半年EPO ,Hb,SaO2 均有显著性差异 (P <0 .0 5或P <0 .0 1 )。结论　在高原缺氧环境下 ,红细胞生成素调节机制紊乱 ,是导致继发性红细胞增多的一个重要环节。     

两种不同方式供氧对新入高原某部官兵血气的影响

目的：观察医用氧气瓶和高原移动式制氧站两种不同方式供氧对新入高原官兵血气的影响。方法按随机抽取原则将40名新入高原1周内的官兵分为A组（医用氧气瓶供氧,氧浓度≧99.5%）和B组（制氧站供氧,氧浓度≧90%）,每组20人,各吸氧40min。在吸氧前和吸氧后30min内抽取动脉血进行血气分析比较。结果（1）A、B两组人员在吸氧前血气指标不具有统计学差异（P＞0.05）,吸氧后两组人员的氧分压（PO2）和氧饱和度（SO2%）均高于吸氧前（P＜0.05）。（2）A、B两组人员吸氧后血气差异无统计学意义（P＞0.05）。结论高原移动式制氧站和医用氧气瓶供氧一样,都能明显提高新入高原人员的氧分压和氧饱和度,提高部队战斗力。     

优秀赛艇运动员两种测功方式的心肺功能比较

本文重点对比了赛艇与自行车两种测功方式的优秀赛艇运动员的心肺功能测试结果,同时横向对比了国内外同类运动员两种测功方式的心肺功能诊断结果,指出,中国优秀赛艇运动员心肺功能的相对水平并不低于国际优秀赛艇运动员,优秀专项运动员心肺功能及通气无氧阈诊断的合理性、有效性是当前值得重视的问题,否则将会影响科研对训练的指导意义。     

Timing the arrival at 2340 m altitude for aerobic performance

This study tested the hypothesis that maximal oxygen uptake (VO(2max)) and performance increase upon altitude acclimatization at moderate altitude. Eight elite cyclists were studied at sea level, and after 1 (Day 1), 7 (Day 7), 14 (Day 14) and 21 (Day 21) days of exposure to 2340 m. Capillary blood samples were taken on these days before performing two consecutive maximal exercise trials. Acclimatization increased hemoglobin concentration and arterial oxygen content. On Day 1, VO(2max) and time to exhaustion (at 80% of sea-level maximal power output) decreased by 12.8% (P<0.05) and 25.8% (P<0.05), respectively, compared with the corresponding sea-level values. Subsequently, these parameters increased by 3.2% (P<0.05) and 6.0% (P<0.05) from Days 1 to 7, by 4.8% (P<0.05) and 5.7% (P<0.05) from Days 7 to 14, followed by 0.7% (P>0.05) and 1.4% (P>0.05) from Days 14 to 21, respectively. These data suggest that endurance athletes competing at altitudes around 2340 m should expose themselves to this altitude at least 14 days before competition.     

The role of haemoglobin mass on VO2max following normobaric 'live high-train low' in endurance-trained athletes

It remains unclear by which mechanism 'live high-train low' (LHTL) altitude training increases exercise performance. Haematological and skeletal muscle adaptations have both been proposed. To test the hypotheses that (i) LHTL improves maximal oxygen uptake (VO(2)max) and (ii) this improvement is related to hypoxia-induced increases in total haemoglobin mass (Hb(mass)) and not to improved maximal oxidative capacity of skeletal muscle, we determined VO(2)max before LHTL and after LHTL, before and after the altitude-induced increases in Hb(mass) (measured by carbon-monoxide rebreathing) had been abolished by isovolumic haemodilution. We obtained skeletal muscle biopsies to quantify mitochondrial oxidative capacity and efficiency. Sixteen endurance-trained athletes were assigned (double-blinded, placebo controlled) to ≥16 h/day over 4 weeks to normoxia (placebo, n=6) or normobaric hypoxia equivalent to 3000 m altitude (LHTL, n=10). Four-week LHTL did not increase VO(2)max, irrespective of treatment (LHTL: 1.5%; placebo: 2.0%). Hb(mass) was slightly increased (4.6%) in 5 (of 10) LHTL subjects but this was not accompanied by a concurrent increase in VO(2)max. In the subjects demonstrating an increase in Hb(mass), isovolumic haemodilution elicited a 5.8% decrease in VO(2)max. Cycling efficiency was altered neither with time nor by LHTL. Neither maximal capacity of oxidative phosphorylation nor mitochondrial efficiency was modified by time or LHTL. The present results suggest that LHTL has no positive effect on VO(2)max in endurance-trained athletes because (i) muscle maximal oxidative capacity is not improved following LHTL and (ii) erythrocyte volume expansion after LHTL, if any, is too small to alter O(2) transport.     

Exercise responses after short- and long-term residence at 2,200 meters

Submaximal and maximal exercise responses were examined in persons (age, 19-30 years) residing at a moderate altitude for different periods of time. Long-term residents (LTR; 44 males, 11 females) had lived continuously between 1,830 and 2,200 m for 2 years or longer before testing. Short-term residents (STR; 22 males, 30 females), previously lowlanders, arrived at 2,200 m within 10 to 21 days before testing. Incremented tests on a motor-driven treadmill were performed until voluntary exhaustion. Cardiorespiratory measures and ratings of perceived exertion (RPE) were examined at 60% and 100% of maximal oxygen uptake (VO2max). With the exception of minute ventilation (VE), which was higher (p less than 0.05) in STR females, maximal responses were comparable in STR and LTR females. All maximal responses were similar in STR and LTR males. Both VE and RPE at 60% VO2max were significantly higher in STR males and females than in their LTR counterparts. Plasma lipid responses to the maximal exercise may indicate a greater contribution of the triglyceride pool of adipose tissue to fatty acid mobilization during exercise in the LTR compared to STR male subjects.