Het is bloedheet buiten dus een koude douche klinkt ineens heel aanlokkelijk. Maar helpt het eigenlijk wel als je wil afkoelen? De meningen lopen uiteen: sommigen kiezen voor ijskoud, terwijl anderen juist beweren dat een warme douche effectiever is. Volgens thermofysioloog Coen Bongers ligt de waarheid in het midden.
Wie bezweet thuiskomt na een warme dag, voelt zich vaak direct beter onder een koude straal. Dat effect is volgens Bongers ook heel logisch: het koude water zorgt onmiddellijk voor een fris gevoel. Toch betekent dat niet automatisch dat het lichaam daarna ook langdurig koeler blijft.
De verklaring zit in de reactie van de bloedvaten. Bij blootstelling aan kou trekken die zich samen om te voorkomen dat het lichaam te veel warmte verliest. Daardoor wordt de afvoer van lichaamswarmte juist tijdelijk afgeremd. Zodra iemand de douche uitstapt, kan het daardoor lastiger zijn om overtollige warmte kwijt te raken.
Op sociale media circuleert al jaren het advies om juist warm te douchen wanneer het heet is. Dat klinkt tegenstrijdig, maar volgens de thermofysioloog zit er wel degelijk een fysiologische logica achter.
Warm water zet het systeem dat verantwoordelijk is voor warmteafgifte aan het werk. Het lichaam reageert onder meer door te gaan zweten, waardoor warmte via verdamping kan verdwijnen. Tegelijkertijd krijgt het lichaam door het warme water ook extra warmte toegediend. Daardoor blijft het daadwerkelijke verkoelende effect beperkt.
Wie zo lang mogelijk van een verfrissend gevoel wil genieten, kan volgens Bongers beter kiezen voor een gematigde temperatuur. Lauw tot licht warm water blijkt vaak de meest effectieve optie.
Dat komt doordat het water nog steeds koeler is dan het lichaam zelf, terwijl de bloedvaten niet zo sterk vernauwen als bij een ijskoude douche. Het lichaam kan daardoor warmte blijven afgeven, waardoor het prettige effect langer aanhoudt.
Er zijn volgens de deskundige nog andere manieren om het lichaam te helpen afkoelen. In medische situaties waarbij iemand oververhit raakt, kan een ijsbad zeer effectief zijn. Voor dagelijks gebruik zijn minder extreme methoden uiteraard geschikter.
Een eenvoudige techniek is het bevochtigen van de huid met een natte doek of spons. Het dunne laagje water dat achterblijft, verdampt vervolgens en voert warmte af. Het principe lijkt sterk op de manier waarop zweet het lichaam helpt afkoelen.
Ook over drankjes bestaan veel misverstanden. Veel mensen grijpen automatisch naar een ijskoud glas water of frisdrank. Dat geeft zeker een aangenaam gevoel, maar het daadwerkelijke effect op de lichaamstemperatuur blijkt relatief beperkt.
Warme dranken zoals thee of koffie kunnen juist de natuurlijke processen stimuleren waarmee het lichaam warmte afvoert. Vanuit fysiologisch oogpunt kan een warm drankje daarom zelfs iets gunstiger zijn dan een koud glas fris. Toch benadrukt Bongers dat de verschillen in de praktijk klein zijn.
Volgens de thermofysioloog draait het uiteindelijk vooral om algemene voorzorgsmaatregelen tijdens warm weer. Voldoende drinken, schaduw opzoeken en zware inspanning vermijden op de heetste uren van de dag hebben veel meer invloed dan de exacte temperatuur van een douche of drankje.
Zijn conclusie is dan ook eenvoudig: kies vooral voor wat prettig voelt. Of het nu een lauwe douche, een glas koud water of een kop thee is, het effect op de afkoeling is aanwezig, maar minder groot dan veel mensen denken.
Bron: RTL Nieuws
wing of kaz has added a photo to the pool:
鹿児島県霧島市、ホテル京セラでアンブレラスカイ / Umbrella Sky at Hotel Kyocera in Kirishima City, Kagoshima Prefecture
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