SYMPATHETIC VASOCONSTRICTOR RESPONSIVE DURING SMALL MUSCLE EXERCISE AGE &SEX

这个子项目是许多研究子项目中的一个 由NIH/NCRR资助的中心赠款提供的资源。子项目和 研究者（PI）可能从另一个NIH来源获得了主要资金， 因此可以在其他CRISP条目中表示。所列机构为 研究中心，而研究中心不一定是研究者所在的机构。 本研究的目的是确定年轻和老年受试者在运动肌肉时交感神经反应是否存在差异。 据推测，老年受试者将有更大的交感神经血管收缩反应比年轻的受试者，如腿部血管电导的变化，在腿部运动过程中，缺血性握力（交感神经刺激）。 对于本研究，将研究总计78例健康受试者。 考虑到脱落，共要求招募100例受试者。将受试者分为6组，每组13人，包括年龄20 - 30岁的男性和女性未经培训的受试者，以及年龄60 - 75岁的经培训和未经培训的男性和女性。 本研究要求每例受试者接受三次GCRC访视。将使用初始筛选访视进行用于入选和排除标准的检查，并确定运动适能水平。 第一次实验访视将获得腿部血流量的再现性数据，以及用于建立后续研究的运动目标点的最大握力和腿部伸展力产生。 在第二次实验访视期间，受试者将在10瓦下进行非优势腿伸展运动。 6分钟后，受试者将在4分钟内以60%的最大力进行静态缺血性握把运动。 然后，受试者将停止握力锻炼，同时继续腿部锻炼。 将在整个运动方案中测量双腿的血流量。 然后将重复该方案，进行更高水平的腿部运动（30瓦）。

This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. The purpose of this study is to determine whether there are differences in sympathetic responsiveness in exercising muscles in younger and older subjects. It is hypothesized that older subjects will have greater sympathetic vasoconstrictor responsiveness than younger subjects, as evaluated by changes in leg vascular conductance in response to ischemic handgrip (sympathetic stimulus) during leg exercise. For this study a total of 78 healthy subjects will be studied. A total of 100 subjects are requested for recruitment to account for dropouts. Subjects will be stratified into 6 groups of 13 individuals consisting of male and female untrained subjects age 20 to 30 years, and trained and untrained men and women 60 to 75 years of age. The study entails three visits to the GCRC for each subject. An initial screening visit will be used to administer tests used for inclusion and exclusion criteria and to determine level of exercise fitness. The first experimental visit will obtain reproducibility data on leg blood flow, and maximal handgrip and leg extension force production used to establish exercise target points for the subsequent study. During the second experimental visit subjects will perform non-dominant leg extension exercise at 10 watts. After 6-minutes there will a 4-minute period during which the subject will perform static ischemic handgrip exercise at 60% maximal force. The subjects will then cease the handgrip exercise while continuing leg exercise. Blood flow in both legs will be measured throughout the exercise protocol. The protocol will then be repeated with a higher level of leg exercise (30 watts).