“If we allow our confidence in fair play to erode, we will undermine the power of sport.”

Michael Phelps — the most decorated Olympian of all time — testified before Congress on Tuesday at a hearing on improving international anti-doping measures.

“In addition to the tests in competitions, I had to notify USADA where I was every day, so they would be able to conduct random tests…outside of competition. This whole process takes a toll, but it’s absolutely worth it to keep the sport clean and fair.”

Phelps expressed frustration with the global anti-doping system.

“I don’t believe I’ve stood up at an international competition, and the rest of the field has been clean. I don’t think I’ve ever felt that.”

Olympic gold medalist Adam Nelson also testified. Nelson was initially awarded silver in Athens — but years later, an athlete from Ukraine who had won gold was stripped of that medal.

“Eight years later, I received a call from a reporter who told me five athletes had tested positive from a retroactive drug testing from samples from 2004,” Nelson said. “A year later, I picked up my medal in the Atlanta airport at the food court. It came with a side of fries and a free toy. Don’t worry about it.”

The U.S. government provides funding to the World Anti-doping Agency.

“At least two Olympic games were corrupted and at the Rio games this past August, scores of Russian athletes competed despite not being subject to credible anti-doping programs,” Travis Tygart said.

“The Rio Olympics were special for me because it gave me the opportunity to end my career on my terms,” Phelps said. “But it was also unique because of increased doping concerns. I watched how this affected my teammates and fellow competitors. We all felt the frustration.”

A House committee will now consider recommendations to improve the global anto-doping system.