The Role of EDHFs on Blood Pressure Following a Bout of Prolonged Sitting

Summary

Canadians spend most of their day in sedentary postures (i.e., sitting, lying, reclining). While the beneficial impacts of physical activity on the heart are well-established, less is known about the consequences during time spent in sedentary postures. Currently, we know that spending time in a bout of uninterrupted sitting disrupts blood pressure regulation. However, it is unknown if there are any 'carry over' effects following uninterrupted sitting bouts (i.e., over the next 24-hours). The release of chemicals from arteries controls how stiff or relaxed they are and is important for controlling blood pressure. This is especially true for arteries directly impacted by sitting (e.g., the popliteal artery behind the knee) and that send blood to the brain (e.g., the carotid artery). We have also established that endothelial-derived hyperpolarizing factors (EDHF, chemicals that relax the artery) are important for the relaxation of the artery the popliteal artery. However, we do not know if the effects of EDHFs on this artery are decreased during or after a bout of uninterrupted sitting. A bout of prolonged sitting also causes blood pressure and fluctuations in blood pressure to increase. Importantly, we reported that fluctuations in blood pressure caused by sitting are higher in young males versus females, but average blood pressure was higher among females. These findings suggest that sitting exerts sex differences in the control of blood pressure. Importantly, these effects were only demonstrated during the 2-hour bout of sitting. As such, it is unknown whether blood pressure is negatively impacted after prolonged sitting. The proposed study will determine the impact of EDHFs on blood pressure regulation following a 2-hour bout of prolonged sitting among a group of healthy males and females. Continuous heart rate (via electrocardiogram) and blood pressure (via finger cuff), as well as blood flow from the common carotid artery (in the neck), middle cerebral artery (in the brain) and popliteal artery (behind the knee) will be measured before and after sitting (via ultrasound). The ability of the popliteal artery to relax will be assessed using ultrasound following the release of a pressure cuff. Finally, 24-hour blood pressure and heart rate will be recorded after sitting using a monitor worn for 24-hours. The role of EDHFs will be investigated by comparing 1) baseline blood flow and blood pressure responses (no sitting), 2) blood pressure responses following a 2-hour bout of sitting, and 3) the blood pressure responses following a 2-hour bout of sitting while suppressing the release of EDHFs (via fluconazole ingestion).

Conditions

• Cardiovascular

Interventions

DRUG

Placebo

Participants will take a placebo sugar pill before and after a bout of prolonged sitting as a control session.

DRUG

Fluconazole 150 mg

Participants will take 150mg of fluconazole, an EDHF inhibitor before and after a bout of prolonged sitting.

Sponsors & Collaborators

• Dalhousie University

  collaborator OTHER

• Université de Sherbrooke

  lead OTHER

Principal Investigators

• Myles W O'Brien, PhD · Université de Sherbrooke

Study Design

Allocation

RANDOMIZED

Purpose

BASIC_SCIENCE

Masking

TRIPLE

Model

CROSSOVER

Eligibility

Min Age

18 Years

Max Age

65 Years

Sex

ALL

Healthy Volunteers

Yes

Timeline & Regulatory

Start

2025-11-01

Primary Completion

2026-12-15

Completion

2026-12-15

Countries

• Canada

Study Locations