A recent survey asked two thousand teens in Taiwan how they spend their free time. The results were surprising. On average, students aged thirteen to eighteen spend about four hours a day on their phones. The percentage of teens who exercise regularly has dropped from forty percent to twenty-five percent over the past decade. Only a small proportion of youngsters say they read for fun every week. Experts say the rate of change is worrying. They suggest that schools set a daily schedule with short intervals for exercise between classes. Even ten minutes of walking can make a difference.

Mr. Chen started running when he was middle-aged, after his doctor warned him about his weight. At first, he could barely run four hundred meters without stopping for breath. He kept a log of every run, writing down the date, the distance, and the duration. Slowly, his pace improved. Ten years later, he finished his first full marathon at the age of sixty. Now a senior citizen, he runs three times a week and trains a group of high school runners on weekends. "Age is just a number," he says. "The absolute key is to keep going."