At what duration of physical activity does hyponatremia begin to become more common?

Hyponatremia, a condition characterized by low sodium levels in the blood, often occurs during prolonged physical activity, particularly in endurance athletes. When physical activity lasts for a considerable duration, typically greater than 4 hours, the risk of this condition increases due to a combination of excessive fluid intake and significant sodium loss through sweat.

During prolonged exercise, individuals may replace fluids without adequately replacing electrolytes, leading to dilution of sodium in the bloodstream. This situation is exacerbated in environments with high heat or humidity, where sweating rates are elevated.

For endurance events or long training sessions, the body's sodium stores can be depleted over time, and if the athlete consumes large amounts of water without electrolyte supplementation, the balance of sodium can be disrupted, leading to hyponatremia. Therefore, understanding the duration of physical activity and its relationship with electrolyte balance is crucial, especially for athletes engaged in events extending beyond 4 hours.