The 36-year-old collapsed during the first quarter of the Indiana game, and was carted off the field and taken to a local hospital in stable condition.
Hart released a statement Monday that he had returned to Ann Arbor and his health was improving. Head coach Jim Harbaugh said Hart returned to work Thursday.
"Couldn't wait to get back," Harbaugh said. "He could have probably been out longer, but he's not ready to get away from greatness said. He came back as soon as he possibly could, and we all appreciated that. He looked great, did a heck of a job. Mike loves the team, the team loves Mike. Great to have him back."
Michigan gave Hart a game ball after Saturday's win. Harbaugh joked that Hart might get another after the Wolverines rushed for 418 yards.
"He's like family to the running back room," said Wolverines running back Donovan Edwards, who had 173 rushing yards and two touchdowns. "We have real feelings toward him and real empathy toward him. When he went down, it was a scary sight for all of us to see. We love Coach Hart tremendously. He's a great guy. He means so much, not only to the running back room but to the entire football team. To have him back today was really a blessing.
"For him to come back ... that just shows the type of person Coach Hart is."
Hart, a record-setting Michigan running back, worked with the backs during warm-ups alongside Fred Jackson, a longtime former Wolverines assistant who stepped in this week during Hart's recovery. When the game kicked off, Hart was in his usual spot on the sideline.
Hart set Michigan records for both carries (1,015) and rushing yards (5,040) while playing from 2004 to 2007.