Although salt tablets are not as popular today as they have been in the past, some athletes still use them to replenish lost electrolytes and the organizers of some prolonged adventure races require their possession by competitors. The entry for electrolytes describes their importance for prolonged exercise; however, salt tablets are generally not considered necessary for competition. During prolonged events or training sessions, particularly in hot or humid climates, fluid and sodium loss can be great. If plain water is provided for fluid replacement throughout the exercise period, hyponatremia can develop. Although salt tablets may be effective in replacing the lost sodium, most researchers suggest consumption of a beverage containing electrolytes for their replacement.