“This is appalling and unacceptable,” Lyons said. “I would like to apologise once again to those individuals and their families.”

Nassar, 54, is serving a life sentence for abusing hundreds of girls and young women while working at Michigan State University and as the team doctor for the US gymnastics team.

“Athlete safety must be at the forefront of everything we do,” said Kerry Perry, who took over as president and CEO of USA Gymnastics in December.

“Like all of you, I was appalled and sickened by the despicable crimes” of Nassar, Perry said. “I want to apologise to all who were harmed by the horrific acts.

“Let there be no mistake; those days are over,” she said. “USA Gymnastics is on a new path, with new leadership, and a commitment to ensure this never happens again.”

University agrees to pay US$500m to victims of abusive ex-Olympic doctor Larry Nassar

Timothy Hinchey, president and CEO of USA Swimming, said his organisation “acknowledges and deeply regrets the abuse suffered by children, athletes and other participants in swimming programmes.”

“Participation in sport should offer physical, social and emotional benefits, but for some, it has resulted in abuse and trauma that will negatively impact the rest of their lives,” Hinchey said. “That is inexcusable.”

The Nassar scandal rocked American gymnastics and led to the resignation of the entire board of USA Gymnastics and CEO Steve Penny.

USOC CEO Scott Blackmun also stepped down amid calls for his resignation.

Ex-Olympic doctor Larry Nassar sentenced to a further 40 to 125 years in prison for child abuse

Nassar pleaded guilty to sexually assaulting women and girls over a two-decade period under the guise of medical treatment.

Olympic gold medallists Aly Raisman, Simone Biles, Gabby Douglas and McKayla Maroney have all come forward and said they were victims of Nassar’s abuse.

Earlier this month, Michigan State University announced it had reached a $500 million settlement with 332 former victims.

Besides USA Gymnastics and USA Swimming, the heads of USA Volleyball and USA Taekwondo also attended the hearing on protecting athletes from sexual abuse and misconduct.

Former Olympian Ariana Kukors Smith filed a lawsuit on Monday against USA Swimming, accusing the governing body of knowing she was being sexually abused by her coach and covering it up.

Also testifying on Wednesday was Shellie Pfohl, the president and CEO of the US Centre for SafeSport, an independent Denver-based body.

The SafeSport Centre is charged with investigating allegations of sexual abuse within the 49 national governing sports bodies in the US.

Pfohl said the centre has received more than 800 reports of abuse during the past 14 months and had permanently banned 142 people from participating in or coaching Olympic sports.

Pfohl said SafeSport was currently receiving 20 to 30 complaints a week and needed additional staff to cope with the workload.

“Far too many of our nation’s athletes have suffered abuse at the hands of perpetrators,” Pfohl said. “If one athlete is abused it’s one too many.

“We believe athletes of all levels deserve to participate in sports that are free from bullying, hazing, sexual misconduct or any form of emotional or physical abuse,” she said. “Anything less is unacceptable.”

Entire USA Gymnastics board resigns after ex-Dr Larry Nassar sexually abused 150 child athletes

Representative Gregg Harper, a Republican from Mississippi, said that there had been a “systematic failure” to protect athletes and that it would take a “Herculean effort to regain the trust of athletes, their families and the American people”.

“Athlete safety must be the top priority of the USOC,” Harper said.

Representative Diana DeGette, a Democrat from Colorado, told the witnesses, “We’re not here to tear down the sporting world.”

DeGette expressed hope that the changes promised by the governing bodies were not “window dressing” but a step down “the road to real change”.