© Copyright National University of Singapore. All Rights Reserved. © Copyright National University of Singapore. All Rights Reserved.

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

© Copyright National University of Singapore. All Rights Reserved.

5HeatManagementStrategies

AEROBICFITNESSCONDITIONING

HEATACCLIMATISATION

PRE-ACTIVITYCOOLING

WORKRESTCYCLES

HYDRATION

© Copyright National University of Singapore. All Rights Reserved.

Hea

t St

rain

Work Tolerance

Max. limit

Start state

Expandingheatcapacity

Lengtheningworktolerance

Reduction

Attenuation

Extension

HeatManagement

© Copyright National University of Singapore. All Rights Reserved.

5HeatManagementStrategies

AEROBICFITNESSCONDITIONING

HEATACCLIMATISATION

PRE-ACTIVITYCOOLING

WORKRESTCYCLES

HYDRATION

© Copyright National University of Singapore. All Rights Reserved.

  Extensiveresearchonfluidreplacement,butlimiteddataonthephysiologicalresponsestodrinksatdifferenttemperatures

Drinktemperatureandform

© Copyright National University of Singapore. All Rights Reserved.

  Extensiveresearchonfluidreplacement,butlimiteddataonthephysiologicalresponsestodrinksatdifferenttemperatures

 Drinktemperatureandformcaninfluencebodyheatstoragecapacity

Drinktemperatureandform

© Copyright National University of Singapore. All Rights Reserved.

Amountofenergyrequiredtowarmorcooltheingestedfluidstobodytemperature

© Copyright National University of Singapore. All Rights Reserved.

ColdfluidswaseffectiveinreducingTcatrestleadingtoanimprovedendurancecapacity

Lee,Shirreffs,Maughan(2008)MSSE

•  Exercise65%VO2peaktoexhaustion

•  Tdb:35°C;RH:60%•  Waterat4or37°C

© Copyright National University of Singapore. All Rights Reserved.

ColdfluidswaseffectiveinreducingTcatrestleadingtoanimprovedendurancecapacity

Work capacity by 23%

Lee,Shirreffs,Maughan(2008)MSSE

© Copyright National University of Singapore. All Rights Reserved.

Amountofenergyrequiredtowarmorcooltheingestedfluidstobodytemperature

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Frombenchtobedsideworksite?

© Copyright National University of Singapore. All Rights Reserved.

 Whileemployingacombinationofvariousheatmitigationwillbemostideal,themeta-analysisallowsprioritizationbasedonresourcesathand

  Ingestionoficeslurryisaneffectiveandpracticalprecoolingmethod  Lesservolumerequiredtoattenuatebodytemperature  Efficacyachievedwithoutaffectingdrinkconstituents

Summary

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THANK YOU

JasonLeePh.D.,FACSMphsjlkw@nus.edu.sg

© 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

© Copyright National University of Singapore. All Rights Reserved.

Dehydrationfollowingracesinthetropics(n=2206)

46%

-Acutedehydration(>2%bodymassloss)maynotcompromisehealthTanetal.(2016).SportsMed

© Copyright National University of Singapore. All Rights Reserved.

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

© Copyright National University of Singapore. All Rights Reserved.

Tanetal.(2016)SportsMed

WaterIntoxication!

PrevalenceofExerciseAssociatedHyponatremiaatOnsiteEnduranceMedicalTents:

2009to2011(n=48)

Dehydration