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Meta-analysis on the efficacy of heat mitigation measures
and optimisation of hydration
Jason KW LEE Ph.D., FACSM Associate Professor
Department of Physiology Yong Loo Lin School of Medicine
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5HeatManagementStrategies
AEROBICFITNESSCONDITIONING
HEATACCLIMATISATION
PRE-ACTIVITYCOOLING
WORKRESTCYCLES
HYDRATION
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Hea
t St
rain
Work Tolerance
Max. limit
Start state
Expandingheatcapacity
Lengtheningworktolerance
Reduction
Attenuation
Extension
HeatManagement
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© Copyright National University of Singapore. All Rights Reserved.
5HeatManagementStrategies
AEROBICFITNESSCONDITIONING
HEATACCLIMATISATION
PRE-ACTIVITYCOOLING
WORKRESTCYCLES
HYDRATION
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© Copyright National University of Singapore. All Rights Reserved.
Extensiveresearchonfluidreplacement,butlimiteddataonthephysiologicalresponsestodrinksatdifferenttemperatures
Drinktemperatureandform
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Extensiveresearchonfluidreplacement,butlimiteddataonthephysiologicalresponsestodrinksatdifferenttemperatures
Drinktemperatureandformcaninfluencebodyheatstoragecapacity
Drinktemperatureandform
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Amountofenergyrequiredtowarmorcooltheingestedfluidstobodytemperature
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ColdfluidswaseffectiveinreducingTcatrestleadingtoanimprovedendurancecapacity
Lee,Shirreffs,Maughan(2008)MSSE
• Exercise65%VO2peaktoexhaustion
• Tdb:35°C;RH:60%• Waterat4or37°C
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ColdfluidswaseffectiveinreducingTcatrestleadingtoanimprovedendurancecapacity
Work capacity by 23%
Lee,Shirreffs,Maughan(2008)MSSE
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© Copyright National University of Singapore. All Rights Reserved.
Amountofenergyrequiredtowarmorcooltheingestedfluidstobodytemperature
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Frombenchtobedsideworksite?
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© Copyright National University of Singapore. All Rights Reserved.
Whileemployingacombinationofvariousheatmitigationwillbemostideal,themeta-analysisallowsprioritizationbasedonresourcesathand
Ingestionoficeslurryisaneffectiveandpracticalprecoolingmethod Lesservolumerequiredtoattenuatebodytemperature Efficacyachievedwithoutaffectingdrinkconstituents
Summary
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THANK YOU
JasonLeePh.D.,[email protected]
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© Copyright National University of Singapore. All Rights Reserved.
0.5
1.0
1.5
2.0
2.5
0 5 10 15 20 25 30 35
Finishing Position
Swea
t Rat
e (l/
h)
Leeetal.(2010).EJAP
Climaticconditions–justoneofseveralfactors
(1)Physicalfitnessandheatacclimationstatus
(3)Exerciseintensity
(2)Amountandtypeofclothingworn
(4)Climaticconditions
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Dehydrationfollowingracesinthetropics(n=2206)
46%
-Acutedehydration(>2%bodymassloss)maynotcompromisehealthTanetal.(2016).SportsMed
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Definition
EAH is the occurrence of hyponatremia during or up to 24 hours after prolonged
activity and is defined by a serum/plasma Na+ concentration below the < 135 mmol/L
EAH is primarily a dilutional hyponatremia
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Tanetal.(2016)SportsMed
WaterIntoxication!
PrevalenceofExerciseAssociatedHyponatremiaatOnsiteEnduranceMedicalTents:
2009to2011(n=48)
Dehydration