US SENATORS are calling for an investigation into the country’s Olympic Committee and USA Gymnastics after former sports doctor Larry Nassar was sentenced to 175 years in prison for molesting athletes in his care.

Democrat Jeanne Shaheen is urging a special committee to look into how Dr Nasser was given unsupervised access to the gymnasts, allowing him to sexually abuse more than 150 women and girls over 25 years.

Her request was announced on Thursday and  backed by senators from across the chamber as the House of Representatives prepares to take up a Senate Bill intended to prevent abuse of athletes.

Set for a vote on Monday, it would require amateur sports groups recognised by the US Olympic Committee to promptly report claims of sexual abuse to police.

In sentencing Nassar to 40 to 175 years in prison, Judge Rosemarie Aquilina called for “a massive investigation as to why there was inaction, why there was silence.”

Shaheen echoed that question in calling for a special Senate committee.

Nassar’s victims “deserve answers to these questions,” Shaheen said, adding that Congress would be putting other young athletes at risk “without institutional accountability” if they don’t investigate the Olympic Committee and its member organisations.

Those victims — 156 of them appeared in the courtroom — gave powerful testimony in court to ensure that Nasser was brought to justice.

Gymnast Rachael Denhollander was among the first victims in September 2016 to publicly accuse Nassar of molesting her and the last to speak at his sentencing hearing.

She said she went to him at 15 suffering from back pain and was sexually assaulted for a year under the guise of medical treatment. During her statement she at times spoke directly to Nassar.

“You have become a man ruled by selfish and perverted desires, a man defined by his daily choices over and over again to feed that selfishness and perversion. You chose to pursue your wickedness no matter what it cost others.”

She also lashed out at those in authority at USA Gymnastics and Michigan State University, where Nassar also worked.

Clasina Syrovy, who competed as a gymnast for 15 years, fought back tears as she confronted him.

“Larry, how many of us are there? Do you even know?” she asked. "You preyed on me, on us. You saw a way to take advantage of your position, the almighty and trusted gymnastics doctor. Shame on you, Larry. Shame on you.”

Olympic gold medallist Aly Raisman initially said she wouldn’t attend the hearing because it would be too traumatic, but the 23-year-old later showed up in court and spoke directly to Nassar.

“You have not taken gymnastics away from me. I love this sport and that love is stronger than the evil that resides in you, in those who enabled you to hurt many people,” she said.

And 15-year-old Emma Ann Miller said MSU was still billing her mother for medical appointments in which Nassar molested her as recently as August 2016, a week before he was fired.

In her statement to the court, Miller directly addressed the university.

“I, like all those that have spoken, didn’t choose this circumstance to have the right to be standing in front of this podium today. Nassar made that choice for us, your 20-year child-molesting employee.”