Control of internal temperature threshold for active cutaneous vasodilation by dynamic exercise.

Area of Science:

• Physiology
• Thermoregulation
• Exercise Physiology

Background:

• Exercise alters the body's internal temperature regulation.
• The precise mechanisms behind exercise-induced shifts in cutaneous vasodilation thresholds are not fully understood.
• Investigating the roles of vasoconstrictor and vasodilator systems is crucial for understanding heat loss during exercise.

Purpose of the Study:

• To determine if exercise-induced increases in the internal temperature threshold for cutaneous vasodilation involve the adrenergic vasoconstrictor system or the active vasodilator system.
• To compare vasodilator and sudomotor thresholds during rest and exercise.

Main Methods:

• 11 subjects underwent local blockade of adrenergic vasoconstrictor control using bretylium tosylate on forearm skin sites.
• Skin blood flow was measured using laser-Doppler flowmetry (LDF) at treated and untreated sites.
• Internal temperatures for the onset of cutaneous vasodilation and sweating were recorded during rest and exercise conditions.

Main Results:

• The internal temperature threshold for cutaneous vasodilation was significantly higher during exercise compared to rest at both treated and untreated sites.
• No significant difference was found in vasodilation thresholds between bretylium-treated and untreated sites, indicating the vasoconstrictor system is not responsible for the shift.
• Exercise did not significantly affect the sweating onset threshold.

Conclusions:

• Exercise-induced increases in the internal temperature threshold for cutaneous vasodilation are mediated independently of the adrenergic vasoconstrictor system.
• The active vasodilator system likely plays a role in adjusting vasodilation thresholds during exercise.
• These findings enhance our understanding of physiological responses to heat during physical exertion.