Does sweating decrease mineral levels?

A friend of mine sweats a lot, especially when she goes dancing. Afterwards, she has cramps: mostly in her calves and feet but also in her hands. She takes magnesium and potium supplements, but these have not solved the problem. She, of course, loses a lot of salt in her perspiration, but she must also lose a lot of other minerals. Can anyone verify this and make some kind of recommendation? Thanks, Henrietta