Drinking water after a massage is often recommended by massage therapists and other health care practitioners, for a variety of reasons. In fact, drinking water in general is a good idea, as the body benefits from proper hydration, and consuming water will help the kidneys and other organs process the various substances which move through the human body on a regular basis.
Drinking water before a massage is also highly recommended, as it will make it easier for the massage therapist to perform deep work by hydrating the muscles so that they are easier to manipulate.
There are primary reasons for people to drink water after a massage. The first has to do with substances released by the muscles as the massage therapist manipulates them, and the second has to do with ensuring that the muscles of the body are properly hydrated.
In the case of the first reason, water after a massage helps the body flush out any accumulated materials in the muscles which were released during the massage. Especially in the case of deep tissue massage, massage stimulates circulation in the body while expressing water, salt, and other minerals from the muscles, and circulation is designed to carry away waste materials generated by cells. By providing the body with plenty of water, massage clients can help sweep away these waste materials; otherwise, they might build up, causing muscle aches and soreness after a massage.