Yes, if you walk on a strenuous trail and lose plenty of body fluids through perspiration it is possible. Through perspiration we lose salts and sugars also known as electrolytes. If we only replenish our bodies with water without replacing electrolytes it can cause hyponatremia. Hyponatremia is the name for a condition where there are abnormal low levels of sodium in our blood. In order to prevent this you need to replenish your body fluids with a sports drink or even better an electrolyte drink. When hiking in hot and humid conditions it is highly advisable to replace water with an electrolyte drink.