Histamine as a Molecular Transducer of Adaptation to Exercise

Exercise promotes and maintains healthy cardiovascular, musculoskeletal, and metabolic function, but the signals and mechanisms which transduce these effects are poorly understood. Histamine plays a role in some of the positive benefits of exercise. The goal of this study is to determine the factors that regulate exercise's effects on endothelial and vascular function, with a focus on histamine released from mast cells in skeletal muscle. Participants will perform exercise or participate in interventions like heating that may replicate some of the effects of exercise. During most experiments, investigators will insert an intravenous catheter in an arm vein and microdialysis probes in the leg, collect dialysate from the microdialysis probe and blood from the vein, record noninvasive measures, and have the participants perform exercise or undergo heating.

This is a series of Basic Experimental Studies with Humans (BESH, as defined by PA-20-184). Subjects are enrolled (non-randomized) in different arms of the overall study.

Subjects will undergo either local heating with diathermy or whole body heating with far-infrared sauna.

Beta-hexosaminidase release from mast cells in mast cell degranulation bioassay when exposed to intramuscular dialysate from exercising individuals

Inclusion Criteria: Age 18 -40 Exclusion Criteria: Systolic ≥ 120 Diastolic ≥ 80 Body mass index (BMI) ˃ 28 kg/m2 Prior diagnosis of cardiovascular disease, diabetes, autonomic disorders, or asthma Smoking or nicotine use Ongoing medical therapy (other than birth control) Ongoing use of over-the-counter or prescription antihistamines Allergies or hypersensitivities to drugs, local anesthetics, skin disinfectants, adhesives, or latex Pregnant, breastfeeding subjects, or planning to become pregnant in the next 12 months Mobility restrictions that interfere with physical activity High physical activity based on International Physical Activity Questionaire (IPAQ1) Non-English speaking