SYMPATHETIC VASOCONSTRICTOR RESPONSIVE DURING SMALL MUSCLE EXERCISE AGE &SEX

本子项目是利用由NIH/NCRR资助的中心赠款提供的资源的众多研究子项目之一。子项目和研究者（PI）可能已经从另一个NIH来源获得了主要资金，因此可以在其他CRISP条目中表示。列出的机构是中心的，不一定是研究者的机构。这项研究的目的是确定在运动肌肉时，年轻人和老年人的交感神经反应是否存在差异。根据腿部运动时腿部血管传导对缺血性握力（交感刺激）的反应，我们假设老年受试者的交感血管收缩反应强于年轻受试者。本研究将对78名健康受试者进行研究。总共要求征聘100名科目，以弥补退学的情况。受试者将被分为6组，每组13人，包括未受过训练的男性和女性，年龄在20至30岁之间，以及受过训练和未受过训练的男性和女性，年龄在60至75岁之间。该研究要求每个受试者到GCRC进行三次访问。最初的筛选访问将用于管理用于纳入和排除标准的测试，并确定运动健康水平。第一次实验访问将获得腿部血流、最大握力和腿部伸展力产生的可重复性数据，用于建立后续研究的运动目标点。在第二次实验访问期间，受试者将进行10瓦的非优势腿伸展运动。6分钟后，受试者将在4分钟的时间内以60%的最大力量进行静态缺血握力练习。然后受试者将停止握力练习，同时继续腿部练习。在整个运动过程中，将测量双腿的血流量。然后将重复该方案，并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).