You hear it almost every massage place you go. After the massage they hand you a cup or bottle of water and say "make sure to drink lots of water today!"
I'm not going to say that those therapists are wrong or are doing anything harmful, but it's something that really irks me. The phrase alone implies that if you don't drink water after the massage, you will suffer consequences. What consequences do they suppose you might suffer?
Here is the common rhetoric I hear from therapists. Soreness, aches, maybe even bruises, all caused by a build up of lactic acid or toxins that I just massaged out of your muscles. Now you must drink lots of water to flush those toxins, otherwise you'll feel terrible the next day.
So. Lots of things wrong with that thinking. 1st massage does not push lactic acid or toxins from your body. Massage is not a detoxifying process. Massage is NOT a detoxifying process.
Lactic acid is removed very quickly from your muscles and reprocessed for cellular repair within 15 mins or a workout, (https://www.ncbi.nlm.nih.gov/pmc/articles/PMC137458/), within hours after extreme workouts (https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2769631/). So it's not a toxin and it's not what causes muscle soreness. And we've known this for decades. Drop this myth.
So does massage release other toxins? What toxins do we suppose are hiding in our muscles and just waiting for a nice relaxing massage to release and flush from our system? Our body is constantly working (very effectively!) to filter and flush any toxin that comes in our body from the outside world. Through our liver, kidneys, lymph nodes, and blood enzymes, our bodies have developed amazing ways to deal with almost any normal "toxin" we will encounter in our daily life.
So why do you feel sore after a massage? Usually the unfortunate culprit is the massage. When we work too deep too quickly, or deeper than your body wants that day, the muscles can get injured. Extreme soreness is never wanted, and in my opinion can further exacerbate the issue you came in for. Some mild soreness may be beneficial in the long run, especially with chronic "tight" feeling or range-of-motion issues you've had for a long time. Getting something to start moving may be better even if it comes with some slight soreness. I don't have studies for this yet, and this opinion could change with our scientific understanding of massage.
I don't tell you to drink a lot of water after a massage. Because I don't want you to hear "or something bad could happen" or "because I need to flush the toxins", because that's just not what science shows us. I have water available freely in my office, and you are more than welcome to bring your own bottle and refill before moving on with your day.
More than anything I ask you to start being more mindful about your body and what your body is telling you, including thirst. Start building that trust in how your body works, this can help lead you to solutions for tight-feeling muscles, painful sore spots, or low range-of-motion. Tune in to that amazing body and let it do what it's meant to.