Hydration is very subjective, however. My inquisitive client got me thinking. Staying hydrated all the time is the key. It's just like sleeping habits. If I only sleep 4-5 hours a night with ambient noise and light, most nights, then sleeping 12 hours on the weekend days isn't going to help much. I get clients who come in with a gallon jug of water and start chugging as soon as they stand up from the table. If they are primarily drinking diet soda and coffee most days, and only have a little bit of water daily, that gallon after the massage is an extreme change. The body doesn't handle extreme changes well. The body prefers consistent, well balanced habits. The gallon chugger probably isn't going to hurt himself, if he is already well hydrated from consistent intake of clean water as a daily practice.So, like getting a good night's sleep regularly, staying hydrated consistently will keep the body functioning optimally before, during, and after the massage.
Check out this nifty Water Intake Calculator with several unit conversions.