Impaired Thermoregulatory Function during Dynamic Exercise in Multiple Sclerosis

Abstract

Introduction Impairments in sudomotor function during passive whole-body heating have been reported in multiple sclerosis (MS), a demyelinating disease of the CNS that disrupts autonomic function. However, the capability of the thermoregulatory system to control body temperature during exercise has never been assessed in MS. Thus, the aim of the present study was to test the hypothesis that thermoregulatory function is impaired in MS patients compared with healthy controls (CON) exercising at similar rates of metabolic heat production. Methods Sweating and skin blood flow responses were compared between 12 individuals diagnosed with relapsing-remitting MS (9 females, 3 males) and 12 sex-, age-, mass-, and BSA-matched CON during a single bout of cycling exercise (rate of metabolic heat production: ∼4.5 W·kg−1) for 60 min in a climate-controlled room (25°C, 30% RH). Results Individuals with MS exhibited an attenuated increase in cumulative whole-body sweat loss after 30 min (MS, 72 ± 51 g; CON, 104 ± 37 g; P = 0.04) and 60 min (MS, 209 ± 94 g; CON, 285 ± 62 g; P = 0.02), as well as lower sweating thermosensitivity (MS, 0.49 ± 0.26 mg·cm−2·min−1·°C−1; CON, 0.86 ± 0.30 mg·cm−2·min−1·°C−1; P = 0.049). Despite evidence for thermoregulatory dysfunction, there were no differences between MS and CON in esophageal or rectal temperatures at 30- or 60-min time points (P > 0.05). Cutaneous vasculature responses were also not different in MS compared with CON (P > 0.05). Conclusion Taken together, MS blunts sweating responses during exercise while cutaneous vasculature responses are preserved. Altered mechanisms of body temperature regulation in persons with MS may lead to temporary worsening of disease symptoms and limit exercise tolerance under more thermally challenging conditions.

Blunted sweating does not alter the rise in core temperature in people with multiple sclerosis exercising in the heat

“…Our collaborative group has recently shown that compared to healthy controls, people with MS demonstrate a blunted sudomotor, but not vasomotor response during moderate intensity exercise at a fixed metabolic H prod (4.5 W•kg -1 ) in a temperate climate (25°C, 30% RH) (1). However, the blunted sweat response with MS was not large enough to alter the rise in rectal and esophageal temperature in that study, possibly due to the relatively cool conditions tested (1). The findings of the present study extend our previous investigations to much hotter conditions (up to T a =35°C).…”

“…It has recently been reported that people with relapsing-remitting MS demonstrate a blunted sudomotor, but not vasomotor response, during moderate exercise at a fixed heat production in a temperate (25°C) environment (1). While this blunted sudomotor response did not result in larger rises in core temperature compared to healthy controls (1), exercise in hotter conditions that approach skin temperature (i.e. 30 to 35˚C) may elicit a net thermal load that exceeds the thermoregulatory capacity of people with MS sufficiently to cause greater rises in body temperature for a given activity level.…”

Abnormal Dynamic Pupillometry Relates to Neurologic Disability and Retinal Axonal Loss in Patients With Multiple Sclerosis

“…Autonomic dysfunction occurs in patients with multiple sclerosis (MS) and can manifest with a range of symptoms including incontinence, urinary retention, gastric and intestinal dysmotility, sexual dysfunction, orthostatic intolerance, vasomotor dysfunction, and sweating and thermoregulatory disorders. [1][2][3][4][5] Demyelination and axonal degeneration affecting the autonomic pathway in the brain stem, hypothalamus, and spinal cord, as well as peripheral autonomic nerve fibers are presumably responsible for such disturbances. Autonomic function tests including urodynamic tests, heart rate responses to deep breathing, Valsalva ratio, sympathetic skin responses, and electrochemical skin conductance are abnormal in patients with MS [5][6][7][8][9] and have been related to the severity of neurologic disability [7][8][9] and lesions detected on brain magnetic resonance imaging (MRI).…”

Prehospital management of exertional heat stroke at sports competitions for Paralympic athletes

“…33 ► Increases in body and/or environmental temperature (without cooling) can exacerbate neurological symptoms, including fatigue, in those with multiple sclerosis, 34 where the sudomotor response to heating is already impaired. 35 Para Athletics Paratriathlon Heat exhaustion 5 Heat-related illness 5 Heat-related illness 30 Limb deficiency ► Display limited body surface area for evaporative and convective heat loss, increasing heat storage. 36 ► Closer coupling of T c and T sk which is further exacerbated by socket liners and prostheses limiting heat dissipation.…”