Scott Blackmun stepped down as chief executive of the USOC, citing health concerns. (Lee Jin-Man/AP)

Scott Blackmun stepped down as chief executive of the U.S. Olympic Committee, the organization announced Wednesday.

In eight years leading the USOC, Blackmun drew praise for repairing relations with the International Olympic Committee and for landing another Summer Games on American soil, but he also withstood criticism for perceived reluctance to intervene in a series of sex abuse scandals, most recently the Larry Nassar case that has engulfed USA Gymnastics and prompted three congressional inquiries.

Wednesday’s announcement came just weeks after USOC board members defended Blackmun and resisted calls from two senators for his resignation over the Nassar case. In a phone interview Wednesday afternoon, USOC board chairman Larry Probst cited Blackmun’s health as a reason for the resignation. Blackmun, 60, is recovering from surgery for prostate cancer and recently learned more treatment is needed, Probst said.

“Given Scott’s current health situation, we have mutually agreed it is in the best interest of both Scott and the USOC that we identify new leadership so that we can immediately address the urgent initiatives ahead of us,” Probst said. “The important work that Scott started needs to continue and will require especially vigorous attention in light of Larry Nassar’s decades-long abuse of athletes affiliated with USA Gymnastics.”

USOC board member Susanne Lyons, a former executive with Visa, will take over as interim CEO.

“Serving the USOC and its many stakeholders and working with our board, our professional staff and many others who support the Olympic and Paralympic movements has not only been immensely rewarding, it has been an honor and the highlight of my professional life,” Blackmun said in a statement. “I am proud of what we have achieved as a team and am confident that Susanne will help the USOC continue to embody the Olympic spirit and champion Team USA athletes during this transition.”

In a phone interview Wednesday afternoon, Probst and Lyons said Blackmun properly handled a 2015 phone call from then-USA Gymnastics chief executive Steve Penny, informing Blackmun that three athletes had complained about Nassar and that Penny intended to contact law enforcement.

Penny contacted the FBI, whose investigation languished for unexplained reasons, and Nassar — a Michigan State University sports physician who sexually assaulted girls and women under the guise of medical treatment — continued to molest patients for more than a year, according to dozens of girls and women who have filed complaints with law enforcement, until another victim contacted Michigan State police in August 2016.

“I think the whole Nassar tragedy should be a wake-up call for all of us: parents, sports organizations . . . and, of course, us at the USOC,” Lyons said.

Sen. Jeanne Shaheen (D-N.H.), one of those who called for Blackmun’s resignation, praised the move Wednesday as “long overdue.”

 “The U.S. Olympic Committee must now bring on new leadership determined to deliver answers and accountability regarding how Larry Nassar was able to freely abuse young girls for decades, as well as answers to questions about abuse in other Olympic programs,” Shaheen said. “It’s clear that the culture at the U.S. Olympic Committee desperately needs to change so that it prioritizes the health and safety of U.S. athletes.”

Blackmun had led the USOC since 2010. He previously served as the organization’s general counsel in 1999 and 2000 and, briefly, as acting chief executive in 2001. After being passed over for the full-time CEO spot that year, he became chief operating officer for Anschutz Entertainment Group, a sports and music entertainment company.

When Blackmun returned nine years later, the USOC was enduring widespread criticism for Chicago’s failed bid to land the 2016 Summer Games. Blackmun enacted a sharp focus at the organization, he later explained, on two goals: Team USA’s competitive success at the Olympics and winning the rights to a future Summer Games for an American city.

“For us, it’s all about medals: How do we help American athletes get medals put around their necks at the Olympic and Paralympic games?” Blackmun said in 2014 at an event at the National Press Club. “And we have a line of sight between every decision that we make today and what’s the impact of that decision going to be on how many Americans can wear Olympic and Paralympic medals.”

Under his tenure, the United States led the medal count at the 2012 and 2016 Summer Games and secured the rights to the 2028 Olympics for Los Angeles. But to abuse victims and their advocates, Blackmun and the USOC’s focus on medals and Olympic bids came at the expense of responding more forcefully to a series of abuse scandals involving Olympic sports national governing bodies that preceded the Nassar scandal, most prominently a series of revelations of mishandled abuse cases by USA Swimming from 2010 through 2012.

“Under his leadership, USOC has focused nearly all its efforts on money and medals while the safety of our athletes has taken a back seat,” John Manly, a lawyer for more than 100 Nassar accusers, said in a statement Wednesday. “It was the courage of these brave women, speaking out about the failure of USOC to protect our athletes, that forced Mr. Blackmun to resign.”

Blackmun has publicly defended the USOC’s handling of previous abuse cases. He further has pointed out he enacted mandatory child protection measures at Olympic sport governing bodies in 2014, and supported the opening of the U.S. Center for SafeSport, a USOC-funded nonprofit that opened last year to investigate suspected abuse in Olympic sports.

Olympic governing bodies are ultimately independent organizations that occasionally have balked at USOC intrusion, Blackmun and others at the USOC have said.

On Wednesday, USOC chairman Probst said the organization is considering requesting changes to the Ted Stevens Olympic and Amateur Sports Act, the federal law that governs America’s Olympic sports organizations, to give the USOC more legal authority to enact changes at sport governing bodies.

“Going forward, we think it’s probably appropriate the USOC have the ability to be more active and have more oversight,” Probst said.