Integrative Strategies to Optimize Metabolic

Integrative Strategies to Optimize Metabolic Performance in the Heat Karl E. Friedl, PhD, COL(Ret) U.S. Army Research Institute of Environmental Medicine Natick, Massachusetts 01760-5007

4th International Conference on Soldier Physical Performance Melbourne, Australia Unclassified

Heat Strain Decision Aid (HSDA)

Potter et al. J Therm Biol 2017;64:78-85 Karl E. Friedl, PhD/[email protected]

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Heat Strain Decision Aid (HSDA)

Should we consider body morphology when assigning personnel to thermally challenging duties? Nigel Taylor, 2017

Can we model aerobic fitness as a separate factor and distinguish high motivation (risk) from more effective cardiovascular response ?

Karl E. Friedl, PhD/[email protected]

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Voluntary dehydration and water taste perceptions

Szlyk et al. Physiol Behav 1989;49:639-47 Karl E. Friedl, PhD/[email protected]

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Taste perception of water

Can we make warm water more palatable?


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Nutrition in the tropics

Have we resolved the 1899 debate about hot weather rations?


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Brown adipose tissue

Yet to be seen: Implications to resting metabolic rate, thermogenesis and weight regulation Karl E. Friedl, PhD/[email protected]

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Capsaicin feeding in humans

WEM 2000;11:152-6 Karl E. Friedl, PhD/[email protected]

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Metabolic control interactions Ground squirrels and camels better tolerate high temperatures (>40 C), in part through decreased sensitivity of TRPV1 (transient receptor potential vanilloid 1) without changing response to capsaicin

Laursen et al. PNAS 2016;113:11342-7 Karl E. Friedl, PhD/[email protected]

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Sleep in the heat 26 C, 50% RH  32 C, 80% RH

Okamoto-Mizuno et al. Physiol Behav 2005;83:759-65 Karl E. Friedl, PhD/[email protected]

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If you stay warm, you can’t sleep!

Based on: Scholander et al. JAP 1958;13:211-218 Karl E. Friedl, PhD/[email protected]

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Meditation and thermogenesis

Benson et al., Nature 1982;295:234-5

Consistent increase in finger and toe temperatures observed in experience Tum-yo meditators Karl E. Friedl, PhD/[email protected]

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Meditation and thermogenesis With advanced meditative practices, resting metabolism could be raised (up to 61%) and lowered (up to 64%), characterized by marked EEG beta activity

Benson et al., Behav Med 2010;16:90-5 Karl E. Friedl, PhD/[email protected]

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Conclusions 1. aerobic fitness is a key modifiable factor that appears to significantly affect heat tolerance and performance in the heat needs to be quantitatively modeled 2. new taste perception biology related to sensations of coolness builds on previous Army investigations to improve drinking 3. fat macronutrient metabolism in the tropics has been a recurring research theme and can be resolved with modern metabolic methods, and underfeeding effects constitute related hypotheses 4. capsinoids increase non-thermal sweating but human studies have not carefully controlled for important moderating factors observed in animal studies or considered new insights to BAT regulation; 5. temperature moderates the quality of sleep but earlier studies on sleep architecture can now be extended outside of the laboratory to devise strategies to optimize restorative sleep in the heat; and 6. neurological control of metabolic rate and body heat production has been demonstrated by specially trained individuals and can be generalized with assistive technologies/real time biofeedback Karl E. Friedl, PhD/[email protected]

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What’s old is new again when reexamined with new methods and technologies


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