Repeated core temperature elevation induces conduit artery adaptation in humans.

Area of Science:

• Physiology
• Vascular Biology
• Thermoregulation

Background:

• Shear stress is a key factor in vascular adaptation in humans.
• The impact of thermoregulatory reflex-induced blood flow and shear on conduit artery adaptation remains unclear.

Purpose of the Study:

• To investigate whether thermoregulatory reflex-induced increases in blood flow and shear stress can induce conduit artery adaptation.
• To determine if lower limb heating can lead to systemic vascular adaptation.

Main Methods:

• Ten healthy young volunteers participated in an 8-week study.
• Participants underwent 3 weekly sessions of 30-minute lower limb heating (40 °C).
• A pneumatic cuff was used on one forearm to restrict reflex-mediated blood flow responses unilaterally.

Main Results:

• Leg heating significantly increased brachial artery shear rate in the uncuffed arm but not in the cuffed arm.
• Endothelial function, measured by flow-mediated dilation, improved in the uncuffed arm after repeated heating.
• No significant changes in vascular adaptation were observed in the cuffed arm.

Conclusions:

• Repeated increases in core temperature via lower limb heating promote upper limb conduit artery vascular adaptation.
• This adaptation is dependent on increased shear stress.
• This study demonstrates a beneficial systemic effect of thermoregulatory reflexes on conduit artery function.