I think that exercise can mobilise mercury and make a person feel worse, so in that way it's not always good for a person. But again, it can help get some of it out through the sweat etc. Not sure if it mobilises it into the brain though, but as mercury can easily cross into the brain, anything is possible.

Usually the things that can move mercury into the brain is taking chelators in the wrong way.

You might find exercise is fine, but don't overdo it as it can take a long time to recover, depending on how poisoned you are and what other things are wrong with you alongside the mercury.

I used to find the best forms of exercise was walking on a treadmill, but I had to be careful as sometimes I overdid it by putting it on an incline, or going too fast or too long. I found that walking on a flat level, for about 20 minutes - 30 minutes at a moderate pace was the best for me personally. But then I have other factors amiss with mercury (long term viral infection). Also rebounding is another very good exercise.