DURHAM, N.C. — Pokemon Go spurred millions of people to collect virtual monsters through the smartphone app and got many of them up and walking. A small Duke Health study suggests the game might have had a health benefit for doing just that. Some users added thousands of steps a day, suggesting that it’s possible to design fun ways to increase physical activity. “Lack of enjoyment and lack of time are the most common reasons for not being physically active,” said lead author Hanzhang Xu, a Ph.D.