"You will love yourself even more afterwards because of how much you have gone through and overcome," Ess said. "And other people probably will never be able to relate. And in a way that's a good thing, because they didn't have the opportunity to have a near-death experience and live."
Mike Lenhart ran this week's Boston Marathon as a guide to an amputee runner who had completed a sports camp operated by Lenhart's Getting 2 Tri Foundation. The two men were about four blocks from the finish line when they heard the bomb blast, which Lenhart said sounded like a garbage truck dropping a Dumpster. He and amputee runner Richard Blalock weren't injured.
Lenhart attests to how science keeps improving an amputee's quality of life. His foundation promotes people with disabilities swimming, cycling, running and racing wheelchairs as a way to integrate in their communities.
"We're at a point in this country where the technology is much more advanced than 20 years ago regarding prosthetic limbs," Lenhart said. "It used to be, 20 years ago, you got an ugly rubber foot and it wasn't very functional. And now they're very functional."
Insurance companies will pay for a prosthetic leg used for walking, but they don't typically cover prosthetic legs used for running or cycling, which can cost between $25,000 and $40,000 each, said Jenna Novotny of the Challenged Athletes Foundation.
That's why the foundation awards annual grants -- $1.9 million to more than 1,200 para-athletes around the world this month -- to pay for the running prosthetic legs and other adaptive equipment, Novotny said. The foundation has also started a fundraising web page for the Boston victims who lost limbs.
Castelli, 27, didn't trust her prosthetic leg at first. Would it support her next step? She spent about six months learning how to walk on it.
After two more months, she learned how to run.
"I feared falling," said Castelli, who was a collegiate softball player when she broke her leg sliding into second base on a steal, leading to infection and ultimately amputation. "And there's always a fear that if I can't run, then it would be a reminder of what my life used to be, that I would never be that speedy little center fielder. My entire life I identified myself as an athlete."
Eight months after she learned how to run, she tested her old identity: She signed up for a women's softball league in West Milford, New Jersey, as the only amputee in the league, she said.
She conquered the amputation in her first at-bat, she recounted proudly.
She hit a home run.
And because the field had no fence and an outfielder chased down the ball, she enjoyed no home run trot.