This study is investigating the role of histamine in generating 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.

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