By Cherri Gregg

by Cherri Gregg

PHILADELPHIA (CBS) — Athletes from all over the country flocked to Philadelphia for one of the nation’s premier triathlon events in Fairmount Park.

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It was the ultimate test: a one mile swim in the Schuylkill River, then a 25 mile scenic bike ride, followed by a six-mile run to the finish.

“It’s kind of organized play for adults, but in order to play, you have to have your gear,” said race announcer Ann Wessling.

She says the 12th annual Trirock Triathlon is very organized, with life guard and medical personnel nearby, so that 3,000 athletes can stay safe while focusing on the challenge.

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“When we first started swimming, we could barely swim 25 yards. Now we can do the whole mile,” said Lisa Widderson.

She and her husband Brian spent four months swimming, biking, running, losing weight, and strengthening their bodies and their bond.

“We’ve been able to spend time together training, which we wouldn’t do otherwise. It’s really been great,” said Brian.

What’s clear: the swim, bike, run challenge takes heart.

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In addition to giving the participants the opportunity to train and raise money, this event raises money for a number of great causes including a half a million dollars for cancer research.