Hi everyone,

Today's podcast is our second-to-last in this heat series. We hope you've enjoyed this small continuous series of the role of heat in muscle physiology and performance.

 

Passive hyperthermia reduces voluntary activation and isometric force production.

Morrison S, Sleivert GG, Cheung SS

Eur J Appl Physiol. 2004 May;91(5-6):729-36. Epub 2004 Mar 11.

 

Abstract

It has been suggested that a critically high body core temperature may impair central neuromuscular activation and cause fatigue. We investigated the effects of passive hyperthermia on maximal isometric force production (MVC) and voluntary activation (VA) to determine the relative roles of skin (T(sk)) and body core temperature ( T(c)) on these factors.

Twenty-two males [VO(2max)=64.2 (8.9) ml x kg(-1) min(-1), body fat=8.2 (3.9)%] were seated in a knee-extension myograph, then passively heated from 37.4 to 39.4 degrees C rectal temperature (T(re)) and then cooled back to 37.4(o)C using a liquid conditioning garment.

Voluntary strength and VA (interpolated twitch) were examined during an isometric 10-s MVC at 0.5 degrees C intervals during both heating and cooling.

Passive heating to a T(c) of 39.4(o)C reduced VA by 11 (11)% and MVC by 13 (18)% (P