The Scientist: Michele Naumann Carlstrom, licensed massage therapist at the Hospital for Special Surgery in New York.
The Answer: If you’ve ever gotten a massage, whether at a spa, a sports medicine facility, or a kiosk at the airport, chances are that your masseuse instructed you to drink a lot of water when you got home (or wherever your travels may have taken you). The reasons for this are twofold.
First off, massages are dehydrating. Kneading and working muscle gets fluid pumping out of the soft tissue and into your circulatory system, where it heads toward your kidneys. That’s why many people have to pee right after a massage. (Naumann Carlstrom says some of her clients can’t get up from the table fast enough.) You have to replenish all that lost water – by drinking more.
Then there’s the issue of metabolic waste, which is produced by muscles in the course of everyday function. When your muscles are tight or you’ve got a major knot, it constricts circulation in those areas, inhibiting the body’s ability to flush out this waste. And, since tight muscles are probably what prompted you to make a massage appointment in the first place, chances are you’ve got some compromised circulation happening. Massage relaxes the tension, releasing the circulatory pathways and allowing nitrogenous metabolic waste to dump into the system. Drinking provides your kidneys with the water they need to effectively eliminate the newly liberated waste. So, once again, it comes back to pee.