Myth busters Monday: Will I boil my horse?

In an effort to blog more often, I am going to try out this Myth busters Monday theme. Looking for myths, old horseman's tales, etc. to tackle so if you have one - comment!

First, a repost of mine from Aug. 2018.

To scrape or not to scrape?

Also known as, will I boil my horse if I leave him out in the sun soaking wet?

Since it's hot as balls a bit toasty again in KY and everyone is sweating, here's some science I thought I'd share.

Disclosure: I am outright stealing this from a post on FB. It is credited to Dr. David Marlin.*

After you hose your horse off, do you scrape the water off or no?

Hot and sweaty at Regionals 2017.

MYTHS

Myth 1 - “You should never put cold water on a hot horse"
Explanation - Ice-cold water(0-5°C) on hot horses does not cause shock, laminitis, kidney damage, muscle damage, tying-up or heart attacks!

Myth 2 - “Water left on a horse will heat up and insulate and make the horse hotter."
Explanation - Flawed physics! Water is a better conductor of heat than air. A wet horse will actually cool faster than a dry one, even if humidity is 100%.

Myth 3 - “Scraping is essential." Explanation - Scraping just wastes time that could be better used putting more water on to cool by conduction. Scraping also wastes water when water is in short supply. Water which could evaporate on the horse. Water evaporating on the ground doesn't cool horses down.

Myth 4 “Concentrate on large veins, arteries inside the back legs, large muscle groups"
Explanation - NO. Cooling by evaporation or conduction works by cooling the blood flowing through the small blood vessels in the skin. The more skin you cool, the quicker you cool the horse. Apply water all over.

I'll admit, I followed the old rule of always hose, scrape, hose, scrape for a long time until I read the actual science behind it. How would I have known any better? But now I just keep hosing Hampton, and then turn him right back out. In the sun! *gasp* No scraping anymore. Here's more:

Evaporation and conduction.

Ideally, I would hose Hampton and then let him sit under a fan for a while. I mean think about it - when it is 95 degrees, and you splash water on your face or over your head, do you get hotter or do you get a cooling effect? 

So there's no harm in the hose, scrape method. But it seems a little pointless.

(Edited to add: Sometimes I will go ahead and scrape off his belly in an effort not to totally soak the barn aisle after he is hosed)

What method do you follow?

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* Dr. Marlin's credentials: 25 years working on equine thermoregulation. 20 plus scientific papers on equine thermoregulation. Working with endurance horses in the Gulf. Advising the racing industry on prevention and management of heat-stroke. Working with Governments on heat legislation. Working with charities on thermal stress. Working on the 1996 Atlanta, 2004 Athens, 2008 Beijing Olympic Games. Currently working on the 2018 Tryon World Equestrian Games and Tokyo 2020 Olympics. Author of the FEI Guidelines for National Federations on the management of horses in thermally challenging conditions.