It went on for close to a year, according to one of the accusers.
When she was 15 years old she broke her back doing gymnastics. That's when she went to see Larry Nassar for treatment, who would come to her gymnastics club, Twistars, once a week.
The former patient says the first time she saw Nassar for treatment for her back, he assaulted her as part of his treatment. She said she wasn't comfortable with it, but once she talked to friends in the locker room who claimed they were dealing with the same thing, she felt it was legitimate.
"It felt more reliable that it was a treatment because it happened to all of us," she testified in curt on Friday.
Another witness say Nassar abused her "countless times" in the back room of Twistars.
She says the first time it happened, Nassar told her "we don't tell our parents about this, they wouldn't understand."
That woman was crying on the stand during her testimony, saying she felt like she was betraying Nassar, who had "helped us in a lot of ways."
Nassar's attorneys argued that he was trying to help them with that treatment. They asked if each of the witnesses' injuries improved after seeing him, which they did in some cases, but the accusers fired back, suggesting it wasn't because of the penetration.
But prosecutor Angela Povilaitis says no matter what happened to their injuries it doesn't match.
"If you believe these victims, and you listen to the defendants, they're at odds," she said on Friday in the courtroom, "and that alone is enough for a question of fact for a jury to decide."