Role of Acetylcholine in Blood Flow Regulation in Healthy Adults: Effects of Age and Exercise Training
Role of Acetylcholine in Blood Flow Regulation in Healthy Adults: Effects of Age and Exercise Training
The overall goal of this study is to address fundamental questions regarding how the molecule
 acetylcholine interacts with the sympathetic nervous system to regulate blood flow and oxygen
 delivery to working skeletal muscle in young and older adults. With advancing age, blood
 vessels supplying active muscle lose their ability to override sympathetic constriction,
 which limits delivery of oxygen and results in fatigue. Findings from these studies will
 serve as the foundation for new strategies to improve regional blood flow regulation in older
 adults and clinical populations, which will increase quality of life and help to preserve
 functional independence.
The ability of blood vessels to dilate is essential to ensure adequate blood flow and oxygen
 delivery to active muscle during exercise. With advancing age, exercising muscle loses the
 ability to overcome vasoconstriction from the sympathetic nervous system, which impairs blood
 flow and limits exercise tolerance. Thus, understanding the signaling mechanisms that
 underlie the ability of active muscle to limit sympathetic vasoconstriction will advance our
 understanding of blood flow regulation in humans and lay the foundation for new strategies to
 improve blood flow and exercise tolerance in aging and clinical populations.

 Therefore, the purpose of this research is to investigate endogenous acetylcholine as an
 important signaling molecule that regulates blood flow during exercise. The studies will also
 determine whether a reduced contribution of acetylcholine explains blood flow impairments in
 older adults. Since exercise training is known to improve acetylcholine signaling, this
 research will also address whether a handgrip exercise training intervention will improve
 blood flow regulation. The expected outcomes will provide new insight to the basic physiology
 underlying vascular control in humans. Furthermore, the findings will provide insight to the
 age-related decline in blood flow regulation during exercise and will assess the use of an
 exercise intervention to improve functional outcomes in older individuals.

 Participants will be asked to complete several study visits over the course of 8 weeks. Once
 study eligibility has been determined, participants will report to the Human Performance
 Clinical Research Laboratory at Colorado State University for a 3 hour visit to assess
 forearm exercise capacity. In a separate 5 hour visit following an overnight fast, a
 physician will place a catheter in the brachial artery of the non-dominant arm to assess
 vascular function. Participants will then complete 7 weeks of handgrip exercise training
 (four sessions per week) and return to the laboratory for follow-up visits to assess forearm
 exercise capacity and vascular function.
Inclusion Criteria:

 -  age 18-35 OR 60-85

 Exclusion Criteria:

 -  recent history of smoking

 -  body mass index greater than 30

 -  history of cardiovascular or metabolic disease, including hypertension or diabetes

 -  medications that may affect outcome measures, such as blood pressure medications or
 hormone replacement therapy

 -  high levels of exercise training, particularly with the forearm (such as weightlifting
 or rock-climbing)