MS and Heat Intolerance: Research Findings

Transcription

1 MS and Heat Intolerance: Research Findings Ollie Jay Thermal Ergonomics Laboratory & Charles Perkins Centre (CPC) Exercise & Sport Science Faculty of Health Sciences, University of Sydney, AUSTRALIA 35.0ºC 35-36ºC 36.0ºC 37.0ºC 32-33ºC 38.0ºC 39.0ºC 40.0ºC 1

2 Thermoregulation control Parsons, 2003 Skin blood flow SKIN BLOOD FLOW Vasodilatation Dilation of the vascular smooth muscle cells allows a greater peripheral blood flow and increase in thermal conductivity Vasoconstriction Blood flow in the periphery (limbs) is drastically reduced due to increased sympathetic activity 2

3 Sweating SWEATING Increases heat loss via evaporation 1 gm sweat = 2427 Joules Eccrine glands (Forehead, back, palms) - heat dissipation Apocrine glands (axillary and pubic regions) - odours PILOERECTION Hairs stand on end in order to trap still air layer against skin Arrector pili muscles attached to the hair follicle involuntarily contract Air Temperature Evaporation Convection Radiation Internal Heat Production Conduction 3

4 Evaporation Latent heat loss SKIN Smith & Havenith,

5 Research: Thermoregulation and MS Co- Principal Investigators: Dr. Phu Hoang Prof. M. Barnett A/Prof. Scott Davis (May July, 2015) USyd: International Research Collaboration Award Ms. Georgia Chaseling (HDR Student) 2015 Incubator grant 2016 Project grant (under review) Dr. Davide Filingeri (Mar Sept, 2015) Endeavour Post-doctoral fellow Thermoregulation in MS QUESTION 1: Is body temperature regulation impaired in people with MS? 5

6 LSR (mg min -1 cm -2 ) Esophageal Temperature ( C) 23-Nov-16 Temperature regulation and MS Younger (20-35 y) and aerobically fit people with relapsing-remitting MS High intensity exercise in 25 C environment CON MS Time (min) Huang et al, 2014 Temperature regulation and MS CON MS Time (min) Huang et al,

7 Thermoregulation in MS Older (~45-60 y) people with relapsing-remitting MS Low intensity (realistic) exercise in 30 C, 30%RH environment Chaseling et al, 2016 Fluid temperature Metabolic Heat Production _ Surface Heat Loss Evaporation Convection Radiation Conduction = Heat Storage + Internal Heat Loss w/cold fluid 7

8 Internal heat loss J/g/ C 250 ml: ~37 kj Cold fluid ingestion: Athletes It has been shown in athletes that ingestion of a cold drink improves exercise time and decreases perceived exertion during exercise in the heat * Lee, MSSE Mundel Exp Physiol Byrne, JAT 8

9 % of Participants remaining 23-Nov-16 Cold fluid ingestion QUESTION 2: Does cold fluid ingestion increase exercise time in the heat for people with MS before heatrelated exhaustion? Methods Results Participants Relapsing-remitting MS participants and age/fitness-matched healthy controls - Every 15-min of exercise drank a) 1.5 C water (CLD), or b) 37 C water (NEU) CON: NEU MS: CLD MS: NEU 30 C, 30%RH 9

10 % of Participants remaining 23-Nov-16 Results MS: CLD: 46.4 ± 14.3 min MS: NEU: 32.7 ± 11.5 min CON MS: CLD MS: NEU 30 C, 30%RH Results MS CLD MS NEU P = 0.70 P = 0.84 P =

11 Future Research Directions Cold water swilling Follow-up study Strategically target cold receptors in the skin that populate certain body regions 11

12 Thermoregulation in MS QUESTION 3: Is the perception of warm and/or cold stimuli impaired in people with MS? Thermosensory anaylser Thermode 12

13 Augment cold stimulus with menthol? Filingeri et al Impact Up to 90% of Australians with MS experience heat-related fatigue Air conditioning costs can be up to 14 times higher in MS households in Australia 13

14 Evaporation 2430 J of heat loss Wenger CB, JAP, J/g J/g/ C 1 g of sweat J/g/ C SKIN Drink or Pour? 250 ml of fluid 15% evaporation 6% evaporation Morris & Jay (2016) Temperature 14

15 Unknowns. 1) The mechanisms for heat-related fatigue are poorly understood: i.e. High core temperature and/or skin temperature work ongoing 2) Ecologically valid interventions are needed work ongoing Thank You for Listening 15