Sweating and MS: Is lack of sweating the reason we overheat during exercise?

[ActiveMSers]

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

Georgia K Chaseling
,
Davide Filingeri
,
Dustin R. Allen
,
Michael Barnett
,
Steve Vucic
, … See all authors
09 DEC 2020https://doi.org/10.1152/ajpregu.00090.2020

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Abstract

Purpose: To determine whether thermoregulatory capacity is altered by MS during exercise in the heat.

Methods: Sixteen MS (EDSS: 2.9±0.9; 47±8 y; 77.6±14.0 kg) and 14 healthy (CON) control participants (43±11 y; 78.6±17.0 kg) cycled at a heat production of 4 W.kg^-1 for 60 minutes at 30˚C, 30%RH (WARM). A subset of 8 MS (EDSS: 2.6±0.5; 44±8 y; 82.3±18.2 kg) and 8 CON (44±12 y; 81.2±21.1 kg) also exercised at 35°C, 30%RH (HOT). Rectal (T_re), mean skin (T_sk) temperature, and local sweat rate on the upper-back (LSR_back) and forearm (LSR_arm), were measured.

Results: All CON, yet only 9 of 16, and 7 of 8 MS participants completed 60 min of exercise in WARM and HOT trials, respectively. All MS participants unable to complete exercise stopped with ∆T_re between 0.2-0.5˚C. The time to reach a ∆T_re of 0.2˚C was similar (MS:28±15 min, CON: 32±18 min; P=0.51). For MS participants completing 60-min of exercise in WARM, ∆T_re (P=0.13), ∆T_sk (P=0.45), LSR_back (P=0.69) and LSR_arm (P=0.54) were similar to CON, but ΔT_b (MS:0.16±0.13˚C, CON:0.07±0.06˚C; P=0.02) and onset time (MS:16±10 min, CON:8±5 min; P=0.02) for sweating were greater. Similarly, in HOT, ∆T_re (P=0.52), ∆T_sk (P=0.06), LSR_back (P=0.59) and LSR_arm (P=0.08) were similar, but ΔT_b (MS: 0.19±0.16˚C, CON: 0.06±0.04˚C; P=0.04) and onset time (MS:13±7 min, CON:6±3 min; P=0.02) for sweating were greater with MS.

Conclusion: Even at 35˚C, a delayed sweating onset didn't alter heat loss to sufficiently affect exercise-induced rises in core temperature. Heat intolerance with MS does not seem attributable to thermoregulatory impairments.

[ActiveMSers]

I have noticed in recent years I'm not sweating as much as I used to. Maybe I'm not exercising as hard? Or it's les humid in Albuquerque (we are in a drought). Anyone else experience this?

[cl3me]

I don’t sweat as much as I should for the level of exertion/temps especially when I’m biking. What sweatvthere is is really salty as well, like crusted on my face. I wondered if that was contributing to overheating. I get pretty red. Worry about heatstroke. Ride earlier in day in summer and take extra water and electrolytes....

[LivWell]

Interesting ... I've noticed this too. While I was still training for events, I'd notice a definite lack of perspiration and would often douse myself with water to help with cooling.

[Suebee]

Ha, I sweat less too with MS! Makes sense that MS might mess up body regulation of sweating. Add it to another odd thing MS does. Too bad it doesn’t also reduce smelly body odors. Possible upside???

But gotta ask, could it be that before ones core temperature is increased that skin temperature is increased enough to slow nerve impulses??? I feel the impact of heat intolerance on my limbs before my entire body decompensates and leaves me in a helpless blob. I usually have enough awareness to stop before that point and cool my body with a/c, ice packs, cold water, drinking cold water, finding shade, etc. before I become immobilized. It alarms my friends who haven’t witnessed this craziness. I usually recover pretty quickly once I get cooler. If you experience heat intolerance for first time, stay calm, know it is temporary and get your temperature down.

Well let’s hope we are all sweating this pandemic less in the new year!