A spokeswoman for Trinity Medical Center in Bettendorf says Greenwood was taken there in critical condition Friday. He's since been transferred to University of Iowa Hospitals and Clinics in Iowa City where he is listed in stable condition.
The Quad-City Times in Davenport reported Greenwood collapsed while working out at Pleasant Valley High School in Bettendorf. Athletic director Randy Teymer told the newspaper that school medical personnel administered to him before he was taken by ambulance to Trinity Medical Center.
A three-year starter for the Hawkeyes, Greenwood, 23, signed a free-agent contract with the Pittsburgh Steelers but was released last week. He earned second-team All-Big Ten honors in each of his last two seasons with Iowa.
Former Iowa safety Tyler Sash, who started alongside Greenwood, tweeted Friday night: "My prayers are with #BrettGreenwood he is alive and on his way to IC. He has overcome every challenge throughout his life. Please keep him in your thoughts and prayers. Most people only knew the football player; I was blessed to know the person as well."
Adam Rittenberg covers Big Ten football for ESPN.com. He can be reached at firstname.lastname@example.org. The Associated Press contributed to this report.