Question

The body loses water and salts in sweat. Explain why drinking large volumes of plain water after exercising may affect the salt balance in the body.

Answer 1

Because it rehydrates the body from the fluids lost through sweat and prevents dehydration

Answer 2

Salts,mostly potassium and sodium are known as electrolytes and the body needs them in very specific amounts for proper function. Any significant imbalance of these levels can even be fatal  if not corrected quickly.The  normal level of sodium in the body is 135 - 145 mmol/l in the blood while  for potassium it's 3.5 to 5.0 mmol /l.Loss of salts e.g. due to sweating  may reduce these levels and so drinking plain water may replenish fluid loss but since plain water has no salts, the salt deficit remains and is in fact aggravated by the increase of plain fluid.But drinking fluid that has  electrolytes  both replaces lost fluids and  and at the same replenishes lost salts keeping the body functioning well .