Importance of Blood Volume and Its Interaction With Cardiovascular Adaptations
试验速览
- 阶段
- 不适用
- 状态
- 进行中（未招募）
- 入组人数
- 36
- 试验地点
- 4
- 主要终点
- Change in vascular conductance of the brachial artery
研究概览
简要总结
The present project aims to investigate the interaction between training-induced blood volume expansion (plasma- and red blood cell volume responses), central as well as peripheral cardio-vascular adaptations. We will investigate cardiovascular responses through one year of training in recreationally active men and women as well as endurance athletes undertaking shorter training-periods/interventions with environmental heat-stress.
The overall purpose with the project is to investigate the physiological effects of prolonged aerobic exercise on central cardiovascular parameters and peripheral effects in the muscle tissue in untrained individuals. Further, we want to compare these effects to exposure to environmental stress (heat) on performance well trained individuals. The present study consist of three parts using the same methodology in different populations to elucidate the above mentioned mechanisms. The first part is a larger training intervention in untrained/recreationally active men and women aiming at evaluating the initial cardiovascular adaptations to an exercise training regimen. In addition there are two parts aimed to elucidate the mechanisms leading to further improvements in cardiovascular and blood volume adaptations from exercise training in a different environmental condition and artificially elevated PV in already highly adapted endurance athletes.
详细描述
Background It is well established that a high maximal oxygen consumption (VO2max) is associated with excellent physical performance in endurance sport disciplines. In order to achieve a high V ̇O2max several things must be optimized as according to the Fick equation. One of the main determinants of VO2max is the oxygen carrying capacity of the blood, which is dictated by the total hemoglobin mass and is significantly higher in endurance athletes than untrained individuals.
Naturally, this system is tightly regulated to maintain a steady blood composition and to promptly recover blood volume if lost due to i.e. hemorrhage but can also be altered by exercise and or exposure to extreme environmental conditions. Changes in blood volume and composition can be seen already after two weeks of conventional exercise training where increases in PV are seen in combination with elevated erythropoietin (EPO) while red blood cell volume remains unaffected. This supports the proposed notion of the kidney acting as a "critmeter" and that a reduced hematocrit due to expansion of PV thereby may regulate erythropoiesis. In already trained individuals i.e. athletes, PV and Hbmass can be further increased through repeated and or prolonged exposure to altitude or hot environmental conditions.
Research questions and hypothesis
- Explore gender and individual differences in the time course and relationship between cardiovascular (central and peripheral) adaptations to long-term aerobic training and the concomitant blood volume changes.
- Evaluate differences between genders and factors influencing individual differences (high vs. low responders) - hypothesizing that female have a blunted cardiovascular response to long-term aerobic training.
- What is the relative significance of blood volume, muscle metabolic and cardiovascular adaptations for performance and aerobic power.
An incremental exercise test on a cycle ergometer will be conducted to determine the maximal work rate and VO2max. Four venous blood samples, each 4 ml, is taken during the rest period. Subjects blood volume and body composition are evaluated with a DXA-scan and CO-rebreathing technique after a brief period of rest following the exercise test.
研究设计
- 研究类型
- Interventional
- 分配方式
- Non Randomized
- 干预模型
- Parallel
- 主要目的
- Basic Science
- 盲法
- None
入排标准
- 年龄范围
- 18 Years 至 45 Years（Adult）
- 性别
- All
- 接受健康志愿者
- 是
入选标准
- •absence of metabolic, chronic diseases, uncontrolled arrhythmia,
- •degree AV-block or sick sinus syndrome
- •no history of smoking or alcohol consumption (≥ 14 items / week)
- •decent acoustic window for echocardiography.
排除标准
- •chronic disease or taking medication
- •history of >2 years of exercise training
- •failure to meet exercise raining criteria
结局指标
主要结局
Change in vascular conductance of the brachial artery
时间窗: 2 hours
Assessment of changes in arm vascular conductance (ml/min/mm/Hg/kg arm mass) to flow mediated dilation, infusion of Acetylcholine and sodium nitroprusside, assessed by ultrasound Doppler.
Blood volume
时间窗: 20 minutes
Training-induced changes in total blood volume (mL) is measured using the Carbon-monoxide rebreathing method.
Maximal systemic oxygen uptake
时间窗: 20 minutes
Training-induced changes in maximal systemic oxygen uptake (ml/min) is evaluated with an incremental maximal cycle protocol on a cycle ergometer
Resting and cycling stroke volume and function measured with echocardiography
时间窗: 90 minutes
LV stroke volume (ml) and LV basal and apical twist (Deg) will be used to measure training-induced changes in LV function during exercise
次要结局
- Mitochondrial biogenesis(60 minutes)
- Cardiac dimentions(90 minutes)
- Fat mass(20 minutes)
- Fat free mass(20 minutes)