The body loses water and satas in sweat explain why drinking large volumes of plain water after excersicing may affect the salta balance in the body

Sodium plays a critical role in balancing components of the body, and a lack of this element can become lethal if a large enough deficit is established. Losing salt through sweat reduces the concentration of Sodium in the body; however, drinking plain water dilutes what is left to a much larger degree (the loss of salt is accompanied by a loss of water, which keeps the concentration of Sodium in the body relatively constant), and this dilution causes consequences.