Impaired Thermoregulatory Function during Dynamic Exercise in Multiple Sclerosis.

Area of Science:

• Physiology
• Neurology
• Exercise Science

Background:

• Multiple sclerosis (MS) is a central nervous system demyelinating disease known to disrupt autonomic functions.
• Previous research indicates impaired sudomotor (sweating) function in MS during passive heating.
• The thermoregulatory capacity during exercise in MS patients remains largely unassessed.

Purpose of the Study:

• To investigate and compare thermoregulatory function during exercise in individuals with MS versus healthy controls.
• To test the hypothesis that MS patients exhibit impaired thermoregulation during metabolically demanding exercise.

Main Methods:

• Compared sweating and skin blood flow responses between 12 MS patients and 12 matched healthy controls (CON).
• Participants engaged in 60 minutes of cycling exercise at a standardized rate of metabolic heat production (∼4.5 W·kg).
• Exercise was conducted in a controlled environment (25°C, 30% RH) to isolate thermoregulatory responses.

Main Results:

• Individuals with MS demonstrated significantly attenuated cumulative whole-body sweat loss at both 30 (MS: 72g vs. CON: 104g) and 60 minutes (MS: 209g vs. CON: 285g).
• Sweating thermosensitivity was significantly lower in the MS group (0.49 mg·cm·min·°C) compared to controls (0.86 mg·cm·min·°C).
• Despite impaired sweating, core body temperatures (esophageal, rectal) and cutaneous vascular responses did not differ between groups.

Conclusions:

• Multiple sclerosis is associated with blunted sweating responses during exercise, indicating impaired sudomotor thermoregulation.
• Cutaneous vascular responses, crucial for heat dissipation, appear preserved in MS patients during exercise.
• Altered thermoregulation in MS may exacerbate disease symptoms and reduce exercise tolerance, particularly in hot conditions.