The thousands of bikers riding on RAGBRAI this summer will be subjects of a public health study. State epidemiologist Patricia Quinlisk says four people will be out among the crowd, checking on “risk factors” such as lack of excercise and people who are overweight.Quinlisk says they hope to learn what motivates someone to make the 450-mile bike ride across the state.And she says they’ll do an analysis of injuries suffered by riders.Quinlisk says they’ll also observe the behavior of RAGBRAI riders, to see how alcohol consumption impacts riders.The Centers for Disease Control has sent an official to lead the survey. RAGBRAI begins Sunday, July 23rd in Council Bluffs and concludes Saturday, July 29th in Burlington. Overnight stops will be in Harlan, Greenfield, Ankeny, Knoxville, Ottumwa and Washington.