Michael Phelps, right, whispers to fellow Olympic gold medalist Adam Nelson as they testify before the House Oversight and Investigations Subcommittee about anti-doping policy in international sport. (James Lawler Duggan/Reuters)

En route to becoming the most decorated Olympian ever, Michael Phelps competed at five Summer Games and six world championships. The mistrust around the swimming pool was so deep, he says now, that not once did he feel those international competitions were completely free of dopers.

“I can’t describe how frustrating it is to see another athlete break through performance barriers in unrealistic timeframes, knowing what I had to go through to do it,” said Phelps, who retired last year with 28 career Olympic medals.

Phelps shared his concerns about international doping with a House Energy and Commerce subcommittee Tuesday, as members explored the international doping system and discussed improvements that could bolster trust in the process and safeguard the integrity of sport at the highest levels.

The Oversight and Investigations subcommittee discussed the Russian doping scandal that clouded last year’s Summer Olympics and sought a better understanding of the authority and function of the World Anti-Doping Agency. Members were at times pointed with their remarks toward WADA and the International Olympic Committee executives who testified.

When Rep. Greg Walden (R-Ore.) was told WADA lacked investigative powers until 2015, he called it a “broken system.” Much of Tuesday’s hearing focused on the complicated relationship between the IOC, the various international sports federations and WADA.

Members of the subcommittee heard about inconsistent testing and practices that vary from nation to nation. Travis Tygart, CEO of the U.S. Anti-Doping Agency, noted that nearly 11,500 athletes competed at the most recent Olympics in Rio de Janeiro. Of that group, more than 1,900 who participated in the 10 sports at the highest risk for doping hadn’t submitted to a single drug test in the months leading up to the Olympic competition.

“It is shocking that over 1,900 athletes hadn’t been tested before the Games and within six months, I have 13 [tests],” Phelps said after the hearing.

In his testimony, Tygart shared many of his oft-repeated concerns and criticisms of WADA to Capitol Hill. He told the subcommittee that inherent conflicts of interest could compromise the body’s ability to root out cheaters, noting that WADA’s governance board includes executives who also run the various international sports federations.

“You cannot both promote and police your own sport,” he said, likening the arrangement to a fox guarding a henhouse.

Both Richard Budgett, the IOC’s medical director, and Rob Koehler, WADA’s deputy director general, told the subcommittee that organizational change is possible and both bodies were open to re-shaping WADA’s governing board.

Budgett explained to reporters later that WADA is currently undergoing a review of its leadership and that presidents and vice presidents from international sports federations should not have positions of influence on the global anti-doping agency.

“Governance of WADA should be independent,” he said.

While the subcommittee invited Phelps and Adam Nelson, a three-time Olympic shot putter, to testify in front of a packed hearing, Congress has limited influence over the IOC or WADA. The United States contributes more money to WADA than any other nation in the world — more than $2 million of the organization’s $27.5 million annual budget.

Koehler told the subcommittee that WADA is not sufficiently funded. He noted that last year’s two-part McLaren Report, which detailed state-sponsored doping that involved more than 1,000 Russian athletes in 30 sports, cost $2.5 million. It now has a six-person investigative team, which is too small, he said, to adequately investigate claims and police the sport around the globe.

“It’s time for change,” he said. “It’s time to put investment in this business. . . . Until that happens, you’ll never see change.”

The members were particularly interested to hear how doping affects the athletes. Nelson brought along his gold medal to share with members and explained that at the 2004 Games, he actually turned in the second-best throw. But the winner, Ukraine’s Yuriy Bilonog, was later busted for doping when his urine sample was re-tested, and Nelson was elevated to first place. Nearly nine years had passed. Nelson told the subcommittee that he received his gold medal at an airport food court in 2013, joking that it came “with a side of fries and a toy.”

Investigators have continued re-testing old doping samples, and more than three dozen medals could be stripped from top finishers at the 2008 Beijing Games, the 2012 London Olympics and the 2014 Sochi Games. Despite the McLaren Report’s findings last year about Russian athletes, the IOC allowed individual sports federations to decide which athletes could compete in Rio. While more than 100 Russian athletes were barred, nearly 300 still participated in the Rio Games.

Asked after the hearing whether it was a mistake to allow two-thirds of the Russian team to compete at Rio, the IOC’s Budgett said, “I don’t know if it was a mistake or not. You have to weigh up, as was said earlier, the balance between individual responsibility and collective responsibility.”

Leaders from 19 national anti-doping agencies, including the United States’, have argued that Russia should be excluded for next year’s Winter Olympics in Pyeong­Chang, South Korea.

Members of the subcommittee said they’ll continue monitoring the IOC’s and WADA’s anti-doping efforts and that another hearing is possible.

“Ultimately, I think this panel, this Congress and the international sports community needs to realize that dealing with Russia, this approach to ensuring clean international competition, the honor system is simply not enough,” Rep. Diana DeGette (D-Colo.) said.