The sweat that is secreted onto the surface of the skin during exercise consists of both water and salt. the sweat is hypo-osmotic to body fluids, meaning that

I think the sweat is hypo-osmotic to body fluids, which means that more water is lost. Sweating involves the production of fluids secreted by the sweat glands in the skin of mammals. Sweat plays an important role in thermoregulation, which is achieved by the water-rich secretion of the eccrine glands.