Running, it turns out, is not a sport for most people in China. And when they do run, their style is, to Western eyes, a bit unusual. Joseph Kahn, a deputy foreign editor for The Times who just returned from five years as Beijing bureau chief, said athletics in China was mostly confined to sports academies that train young people to be Olympians. Otherwise, exercise takes place in the morning in parks, where people do yoga and tai chi and run backward, which they think helps with balance.

“Rarely do people run on the streets, but not never,” he said.

Some athletes who have competed in Beijing said they were defeated by the conditions there.

Jeremy Horgan-Kobelski, a mountain biker, entered a race in Beijing last September. He started coughing soon after the race began, and his coughing fits were so severe that he had to drop out halfway through. Almost everyone had trouble, he said, with only 8 of 50 cyclists finishing the race.

Still, you can avoid the worst of one pollutant, ozone, by running in the morning. Levels peak at midday. And there is some evidence that you can develop tolerance to ozone over a five-day period, said Kenneth W. Rundell, director of respiratory research and the human physiology laboratory at Marywood University in Scranton, Pa.

Added to the air pollution is the pollen. The Chinese government has warned that August is pollen season, and counts are expected to be high. I’m bringing over-the-counter pills containing the decongestant pseudoephedrine, a drug that is banned for Olympians under antidoping regulations but is legal for non-Olympians like me.

But Randall L. Wilber, a senior sports physiologist at the United States Olympic Training Center, told me that heat and humidity would take a bigger toll. “We’re actually focusing very, very heavily on heat and humidity as opposed to air pollution,” he said.

Endurance athletes who exercise in heat and humidity can become acclimated in about two weeks. The body adjusts by increasing the plasma volume, making it easier for the heart to pump blood to muscles and to the skin, for cooling. In addition, when you are acclimated, sweating starts sooner and the sweat is more profuse and more diluted.