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

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 (Tre), mean skin (Tsk) temperature, and local sweat rate on the upper-back (LSRback) and forearm (LSRarm), 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 ∆Tre between 0.2-0.5˚C. The time to reach a ∆Tre 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, ∆Tre (P=0.13), ∆Tsk (P=0.45), LSRback (P=0.69) and LSRarm (P=0.54) were similar to CON, but ΔTb (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, ∆Tre (P=0.52), ∆Tsk (P=0.06), LSRback (P=0.59) and LSRarm (P=0.08) were similar, but ΔTb (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.

Acute Thermoregulatory and Cardiovascular Response to Submaximal Exercise in People With Multiple Sclerosis

“…These results are comparable with those of a recent work by Chaseling et al. ( 15 ), who showed that the time taken to reach a rise in rectal temperature of 0.2°C, often considered as lower limit of Uhthoff’s phenomenon threshold, was not different between PwMS and control group. This suggests, again, similar kinetic adaptation of CBT to submaximal square wave exercise.…”

“…Therefore, it seems that the typical workload of a 6MWT did not produce a surplus of heat in the PwMS group which may have abnormally raised the CBT, nor the late adaptation of the CBT to the exercise bout have produced any monotonic increase which may suggest a pathologic disruption in the mechanism of thermal dispersion from the body. These results are comparable with those of a recent work by Chaseling et al (15), who showed that the time taken to reach a rise in rectal temperature of 0.2°C, often considered as lower limit of Uhthoff's phenomenon threshold, was not different between PwMS and control group. This suggests, again, similar kinetic adaptation of CBT to submaximal square wave exercise.…”

“…Allen et al (1) observed no differences in temperature (both esophageal and rectal) after 30 and 60 minutes of cycling exercise in a controlled environment (25°C, 30% relative humidity) between PwMS and healthy subjects. More recently, Chaseling et al (15) compared the rise in rectal temperature and the sweating response between PwMS and healthy subjects exercising in warm and hot environments, and concluded that Uhthoff's phenomenon is not related to rises in CBT. Other two studies considered the effects of the increased CBT caused by moderate aerobic exercise both on sensory and cognitive functions in PwMS, concluding that exercising in warm conditions decreases cold skin thermosensitivity (16,17).…”

An American Physiological Society cross-journal Call for Papers on “Inter-Organ Communication in Homeostasis and Disease”

“…The editorial expertise at AJP-Regu is necessarily broad; thus, AJP-Regu would welcome submissions evaluating the inter-organ communication of most organ systems. However, AJP-Regu is particularly interested in studies examining the interplay of multiple organ systems in the setting of chronic inflammation or diseases such as diabetes and obesity, and with interventions such as exercise (61). AJP-Regu is also very interested in the multi-organ adaptations to pregnancy and diseases of pregnancy, and the interaction between maternal and fetal organ systems (62).…”

“…This also includes studies examining how physiological or pathophysiological changes during pregnancy lead to maladaptions in the offspring in the perinatal period or long term. Although many of our manuscripts focus on rodent models of physiology or are conducted in humans (61,63,64), the scope of AJP-Regu is certainly not limited to that of human physiology or studies utilizing traditional models of human disease states. Our authors utilize humans subjects, traditional (for example, rodents) and nontraditional models of human disease, and are examining the biology of a wide variety of mammalian and non-mammalian species, including sheep (62,65,66), chickadees (67), seals (68,69), and bullfrogs (70)!…”