If you're thirsty, go right ahead. Please drink some water.
But if you're not thirsty, it's really no big deal. You don't HAVE to drink water JUST because you got a massage.
Let's break down this rather persistent myth.
#1: TOXIN VAGARY
The most common answer given as to why people should go out of their way to drink water post-massage typically involves vague references to how "toxins" are being "pushed out" during massage, and so need to be "flushed" or "rinsed" out of the body thereafter. There's a few problems with this line of thought.
The term "toxin" in this context is rather non-specific and not very useful. Are we talking about compounds that are naturally present in the body? Like lactic acid? Metabolic wastes? Or something that's actually toxic and isn't naturally present the body, like snake venom? Preservatives? Pesticides? Using language that's not specific and also evokes fear and confusion isn't useful. After all, who wants toxins running amok in their body? Better flush them out quick!
From here on out, I'll use the word compound instead of toxin.
However, even IF massage therapy could "push" compounds out of the muscle tissues (which evidence does not support), what then is the mechanism that would allow drinking water to consequently "flush" them out?
On to number two...
#2: WE'RE NOT CAR WASHES
The body is pretty darn good at processing aaall kinds of compounds. The job of processing those compounds belongs to the liver and kidneys. Stuff in our blood stream eventually makes it way through the liver and kidneys, gets sorted, and the stuff that's not useful is then lined up for excretion (pee, poo, sweat, etc).
The body is also pretty darn good at regulating water levels in the blood and cells. It cleverly lets you know you need more via thirst. And (unless due to environmental circumstances) the chances you'll dip below a level that is health threatening is extremely rare.
When we drink water, our body certainly makes use of it, and what it can't use, heads on out. Water does not make a detour to "flush" over our recently massaged muscle tissues, like some kind of car wash. We can't just pour water into one end and all our gook and grime is rinsed away down the drain.
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All that being said, if you're thirsty, drink some water. If you haven't had anything to drink in a while, sure, maybe you should fill a glass. If you don't drink water hardly at all, you should probably up that game. I'm an advocate for being hydrated. Water's great. No contest there. If a client expresses they are thirsty, I'll gladly get them something to drink.
But, just to be clear, it's not required to chug a bunch JUST because you got a massage. Our body and its systems are complex and fascinating - far more than simple car washes.