Portugal’s Joao Vieira defied “hell” in the 50km walk in Doha to become the oldest person to win a medal in World Championship history.
The 43-year-old took silver behind Japan’s Yusuke Suzuki as the heat continued to hamper athletes.
“For me, it was hell – very, very hot,” Vieira said. “How did I cope? Just a lot of ice and cold water.”
On Friday, 28 runners withdrew from the women’s marathon because of 32C temperatures despite a midnight start.
Vieira criticised the 23:30 start time after finishing the race in four hours four minutes 59 seconds.
“That’s the time to leave a nightclub. I usually go to sleep at 10 o’clock in the evening,” said Vieira, who added to the 20km bronze medal he won at the 2013 World Championships in Moscow.
French world champion decathlete Kevin Mayer has said that holding the event in Qatar was a “disaster” for athletes because of the heat and humidity.
Track and field athletes will be aided by an air-conditioned stadium which reduces the temperature to 23C, but the marathon and walking races are held outside the arena.
Following criticism, athletics world governing body IAAF said it took extra precautions for the 50km walking races by increasing the number of refreshment points and the presence of medical staff.
In the men’s race, 14 walkers dropped out from a field of 46 as Canada’s Evan Dunfee took bronze.
Four were disqualified, including Britain’s Cameron Corbishley and Dominic King.
Six of 24 competitors did not finish the women’s 50km race, which started at the same time.
China’s Liang Rui won gold in 4:23:26 ahead of compatriot Li Maocuo and Italian Eleonora Anna Giorgi.