The VnExpress Marathon Quy Nhon 2026 kicks off on the morning of 13/9. According to the Trung tam Du bao Khi tuong Thuy van Quoc gia, the area will experience moderate rain with temperatures between 25-30 degrees C. While these conditions are cooler than the usual intense heat of the coastal city, this comfortable feeling could lead runners to overlook the importance of replenishing water and electrolytes throughout the race.

Runners compete in the rain at VnExpress Marathon All-Star 2026. Photo: VnExpress Marathon

Why rain still causes dehydration

Many runners mistakenly believe that they only need to drink when they feel hot or thirsty while running in the rain. In reality, high humidity makes it harder for sweat to evaporate and cool the body. The body continues to work hard and sweat constantly, leading to rapid water loss.

John Gallucci Jr., chief executive officer of JAG Physical Therapy in the US, stated in Peloton magazine that cold rainwater cools the body's surface. As a result, the central nervous system does not signal thirst, even though the body continues to lose water through sweat.

By the time runners actually feel thirsty, their bodies are already severely dehydrated, resulting in cramps and a quick decline in stamina.

Avoid excessive plain water

Another common mistake is consuming too much plain water at aid stations. When sweating heavily, the amount of sodium in the blood already decreases significantly. Continuously consuming large amounts of plain water in a short period will further dilute the remaining small amount of sodium.

This condition, known as hyponatremia, causes bloating and nausea. In severe cases, runners may experience water intoxication.

According to Doctor Lewis Nelson, chair of the Emergency Department at Rutgers New Jersey Medical School in the US, hyponatremia is a dangerous phenomenon common among marathon runners due to the overuse of plain water.

A study published in The New England Journal of Medicine recorded that 13% of athletes suffered from hyponatremia because they consumed more plain water than their kidneys could excrete.

When blood sodium is diluted, osmotic pressure within cells becomes imbalanced. Water floods into cells, causing swelling, which leads to heavy legs, stomach gurgling, and dizziness during the race.

Utilize aid stations to accurately replenish electrolytes on schedule. Photo: VnExpress Marathon

Proper hydration strategies

Runners should not wait until they feel thirsty to drink. The correct approach is to drink small sips regularly every 15-20 minutes. This balances the body's water levels and prevents stomach overload.

Doctor Bui Phu Truong, head of the VnExpress Marathon medical team, recommends a specific intake of 100-150 ml every 15-20 minutes. For long distances, runners can supplement with salt tablets every 45-60 minutes.

Regarding beverage choice, prioritize drinks containing sodium and sugar. These two components optimize water absorption and prevent hyponatremia during long-distance running.

After crossing the finish line, runners should not sit or lie down immediately. Instead, walk gently and continue to slowly replenish water and electrolytes during the first 30-60 minutes.

This practice helps rebalance lost minerals, reduces muscle soreness, and prevents a sudden drop in blood pressure.

On the morning of 13/9, 8,000 athletes will compete in three distances: 5km, 10km, and 21km at Nguyen Tat Thanh Square. The 21km race starts at 4h, followed by the 10km at 5h, and the 5km at 5h30.

Duc Anh