Just for surviving after two failed kidney transplants and living long beyond the prognosis of six months he was given at age 20, Shad Ireland was already a something of a walking improbability.
The 37-year-old living with no working kidneys has taken his status as a medical marvel much further, though, performing physical feats most normally healthy people wouldn't even dream of, despite spending most of his life on dialysis.
"For me to be on dialysis for 27 years, for me to do two triathlons, has really got the medical community scratching their heads," Ireland said. "If you asked any doctor, if you told them about me, they would say it's impossible."
Last week Ireland took his determination 4,639 miles. He biked from California to the steps of the U.S. Capitol Building to draw attention to the 500,000 people with kidney failure currently living on dialysis.
More importantly, however, Ireland said, he biked across the country to get the attention of the millions of Americans whose obesity, high blood pressure or diabetes put them at risk for kidney failure.
To make it across the country, Ireland had to schedule four-hour long dialysis sessions every Monday, Wednesday and Friday to clean the toxins out of his blood that a healthy kidney would have rid him of. Doctors say kidney disease makes conditioning for any physical task much more difficult.
"When I said I was going to do an Ironman triathlon, my biceps were the size of quarters. I went to a gym. I had no idea what I was getting into: I couldn't walk two minutes on a treadmill, I couldn't pick up 10 pounds," Ireland said. "Within a year I was able to gain 42 pounds of muscle."
Like the other 500,000 people in the United States living with kidney failure, Ireland had a body that was ravaged by dialysis and his disease. Many dialysis patients are unable to work, they may suffer from bone loss and end up in a wheelchair, and 15 percent to 20 percent of people on dialysis die every year.
"Healthy kidneys remove these things (toxins) every second of every day, so there is very little accumulation and the concentration of these chemicals in the blood stays within a very tight range," said Dr. Alicia Neu, a professor at Johns Hopkins University School of Medicine in Baltimore.
"Many of these substances can affect physical strength, endurance, memory, sleep habits, etc.," said Neu. "Many patients can and should remain physically active on dialysis. They may need to work harder and certainly have more to overcome to achieve the level of activity of those who have normal kidney function."
Ireland's physical feat might seem impossible to many, but doctors want their dialysis patients to think the opposite.
"No it's not impossible -- it's fantastic," said Dr. Robert Stanton, the chief of nephrology at Joslin Diabetes Center in Boston.
"The idea of trying to get people to exercise has been talked about for years," said Stanton, who is also a professor of medicine at Harvard Medical School. "Look, there is no reason that you have to be sitting around and feeling ill. If you get up and moving you can really take charge of your life."
Stanton explained that the benefits of exercise -- such as lower blood pressure and increased bone strength -- often counteract the secondary health conditions caused by kidney disease.
"But most patients find it tiring or draining after dialysis," he said.
In dialysis, a patient crams in 48 hours of blood-cleaning time into a four-hour window. Stanton said the process leaves most of his patients so exhausted that they go home and lie down. But by not exercising, dialysis patients can fall into a tailspin of ill-health and low physical activity.
To motivate people, Stanton said he often tells patients about a study that took professional athletes and enforced a week of bed rest. The goal was to measure how quickly the body and organs weaken from inactivity.
"On average it took six weeks of hard training to get back from one week of bed rest," he said. Then to think of Ireland's lifelong dialysis treatment leading him to a triathlon does more than amaze people familiar with kidney failure.
"Shad would be a very inspirational fellow to most individuals, even those without kidney disease," said Dr. Leslie Spry, spokesperson for the National Kidney Foundation.
Unlike many dialysis patients, who end up with kidney disease from diabetes or high blood pressure, Ireland had a poorly-understood autoimmune condition, membranoproliferative glomerulonephritis or MTGN, that attacked his kidneys.
"My kidney failure started when I was 10 years old," said Ireland. "This all started with a promise I made to myself in the early '90s when I lost my first kidney transplant."
Ireland said he was lying on the couch, weighed 79 pounds and was barely able to move when he was inspired by footage of two women dragging themselves to the finish line of a triathlon. It took nearly a decade, but in 2003 he was healthy enough to start training.
Yet while Ireland biked for awareness for people already on dialysis, he said his main mission is prevention and funding for the people who may be at risk for kidney disease.
"An hour a day, four days a week is what I advocate," Ireland said. "I wasn't an athlete. When I started this I had no athletic background."
Ireland said he rode to the steps of the Capitol, in part, because of the health-care reform debate going on in Congress and the great amount of money spent caring for dialysis patients every year.
Experts estimate that the 500,000 people on dialysis -- a small fraction of the 300 million total polulation of the country -- account for 6 percent of all Medicare costs.
"Dialysis patients are hospitalized three to five times per year. If you look at the base costs, just to walk through the door is $3,500," Ireland said. Since he began exercising, Ireland said he's been hospitalized less often.
"I've been hospitalized twice in eight years," he said, and those saved costs would just be the beginning. Now Ireland is advocating for testing and prevention funding for kidney failure.
"It's not about cutting, it's about reallocating resources," he said.
ABC News' Dan Childs and Lisa Stark contributed to this report