"It brings together so many people in support of heart babies or heart families, its such a wonderful experience," said Phoebe Kaufman, whose youngest daughter, Baya, had open heart surgery at CHOP when she was only 4-days-old.
Now, the toddler is healthy.
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The annual indoor cycling fundraiser supports children like her, who are born with heart disease.
"Last year was our first year and I thought, 'well I'm in pretty good shape, this will be alright.' I couldn't last 10 minutes on that bike. It was pretty intense," said Kaufman.
About 500 more supporters attended the event this year. Last year, it raised more than $400,000.
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Larissa Kim from team Va Va Voom says it's worth the sweat.
"When you're riding and you feel the energy and seeing the pictures of the children, it empowers you to pump and bike even harder," Kim said.