Michael J. Joyner, M.D.

The purpose of this study is to develop a single, standardized test to determine how individuals tolerate acute hypoxia in a stepwise fashion. We aim to evaluate the association between multiple factors, such as ventilatory compensation, heart rate response, acid-base changes, sex, pulmonary function, etc, which may explain why some individuals tolerate exercise in hypoxia better than others. Identifying these factors of association will inform future pharmacological and non-pharmacological attempts to combat acute hypoxic exercise.

The purpose of this study is to to better understand the relationship between autonomic neurovascular function and hot flashes associated with menopause.

The purpose of this study is to evaluate performance of already developed porcine algorithms in the human “models” of lower body negative pressure (LBNP), and to obtain human model training and validation data sets from LBNP for further refinement of the algorithms.

The purpose of this study is to investigate whether the autonomic support of blood pressure alters after menopause in women, the importance of female sex hormones in blood pressure control, and the potential for exercise training to provide a therapeutic pathway that might limit increases in blood pressure in this population.

The purpose of this study is to investigate the effects of long-COVID (sometimes called post-acute sequelae of COVID 19 or PASC) on breathing during exercise. The hope is to find differences in breathing patterns between people with long-COVID and people without to better develop treatments to improve feelings of breathlessness in patients with long-COVID.

The purpose of this study is to better understand how the nervous system responds to changes in blood pressure and carbon dioxide levels

The purpose of this study to better understand the central mechanisms contributing to sympathetic discharge patterns in humans.

The goal of the project is to develop and implement the optimized carbon monoxide rebreathing techniquein order to estimate blood volume.

The purpose of this study is to find the doses needed of sodium nitroprusside and nitroglycerin to get an equal response, assessed by forearm blood flow.

The purpose of this study is to determine if the respiratory muscle activation pattern during inspiratory pressure threshold loading (IPTL) affects resting limb blood flow and muscle sympathetic nerve activity (MSNA).

The purpose of this study is to use lower body negative pressure (LBNP) to evoke central hypovolemia as a non-invasive surrogate to hemorrhage during IV infusions of epinephrine and saline to determine the robustness of the ISR algorithm.

We will determine if a) glycyrrhetic acid (GA, a key component of TJ-68) evokes vasodilation, and b) if glycyrrhetic acid alters the TRP mediated sensory response to local heating. 

The purpose of this study is to assess the physiological effects of Glycyrrhetic acid and the other components of TJ-68 on healthy people.

The goal of this study is to determine how neuromuscular fatigue in exercising muscle is influenced by local vs. global oxygen deficit. 

The purpose of this study is to determine how oxygen binding to hemoglobin affects gas exchange during exercise in humans. 

The goal of this study is to determine how oxygen binding to reduced levels of hemoglobin affects the acute responses to oxygen delivery in exercising muscle in humans.

This study will explore the effects of delivering a common nebulized drug taken by Cystic fibrosis (CF) patients during exercise.

The purpose of this study is to verify this finding in a cohort of experienced cyclist. If the aerobar position indeed decreases quadriceps oxygen saturation, there can be implications for musculoskeletal fatigue and/or athletic performance.

The purpose of this study is to determine if the near-infrared spectroscopy  (NIRS) and electromyography (EMG) signal during isometric handgrip exercise is reproducible within subjects (for the same and different limbs) and between subjects.

To determine if lidocaine administered in the brachial arteries of volunteers alters the vasodilator responses to a brief forearm contraction and bolus infusions of the vasodilators acetylcholine and nitroprusside. 

The purpose of this study is to see how the body responds to different levels of lower body negative pressure, specifically how the peripheral blood flow responds to these levels of lower body negative pressure.

Blood pressure rises in postmenopausal (PM) women and may be caused by widespread microvascular vasodilator dysfunction in conjunction with increased efferent sympathetic vasoconstrictor nerve activity. The goal of this study is to measure the effects of regular physical activity on vasodilator effects of acute administration of estrogen in postmenopausal women.

The purpose of this study is to see if regular exercise has an impact on blood flow to the brain.

The purpose of this study is to compare measurements of muscle oxygen transport between two different types of NIRS devices (CW-NIRS and FD-NIRS). Specifically, indices of muscle mitochondrial capacity, perfusive and diffusive oxygen conductance during exercise, and muscle microvascular function will be investigated. We will also explore individualized normalization strategies to minimize discrepancies between these technologies.      

Sleep apnea is the most common form of sleep disordered breathing and patients with sleep apnea exhibit persistent activation of the sympathetic nervous system.  Sympathoexcitation is also the final common pathway for complications in conditions like obesity, hypertension, sleep apnea, and heart failure and plays a significant role in predicting negative clinical outcomes. However, the mechanisms of sympathoexcitation with sleep apnea are poorly understood and thus make effective therapeutic approaches difficult to develop. Intermittent hypoxia (IH) has been implicated in animal models as the primary stimulus for evoking increases in sympathetic activity with recurrent apneas. The overall goal of this application is to better understand the effect of IH on sympathetic discharge patterns in humans as well as the mechanisms mediating persistent sympathoexcitation with IH.  

The purpose of this study is to learn how uterine fibroids may be connected to heart disease and high blood pressure. It is not known what causes fibroids, but they frequently occur in women who also have high blood pressure, heart disease, and stroke. The investigators of this study want to learn if certain changes in the blood vessels or nerve activity can put women at risk for these diseases and for fibroids.

The primary objectives of this study are to confirm the safety and activity of etavopivat at modifying hemoglobin and shifting the O2 dissociation curve to the left, and to quantify the changes in blood flow and oxygen delivery during small muscle mass exercise, and maximal exercise capacity (V̇O2max), lactate, and other biomarkers during whole body exercise under normoxia and hypoxia following treatment with etavopivat.

The purpose of this study is to see if age, sex hormones and regular exercise impact blood flow in healthy women.

The purpose of this study is to characterize the ventilatory response to exercise in females with HFrEF and determine if mechanical ventilatory constraint occurs during exercise. Also, to determine if ventilatory constraint affects exercise tolerance in patients with HFrEF, by alleviating mechanical ventilatory constraint via a helium (He) backed inspirate during exercise.