Sarah Knowles claimed a Guinness Book record running her very first half marathon.

And that accomplishment was secondary, almost an afterthought, easily surpassed by her son's smile.

Matthew Knowles, 13, has spent most of his life isolated in his own world, unable to talk or walk because of a rare abnormality in his chromosomes. In 2005, his parents, Sarah and Adrian, introduced him to the horse-riding therapy program at LifeStriders in the Town of Delafield and watched him blossom.

"When Matthew first started, he could barely sit up," Sarah Knowles said. "He wasn't interested in looking at anyone. He wouldn't make eye contact.

"He's a different child now. He can sit up straight. He can walk; the motion of the horses makes his leg muscles work. He'll reach for the volunteers. It's just unbelievable."

Supporting LifeStriders motivated Knowles to run the Trailbreaker Half Marathon on April 6, roped together with 102 others as part of an effort to set a new mark for the Guinness Book of World Records.

It was an expanded version of the Jennipede that set a similar record (since broken) with 62 tethered together in the 2011 Lakefront Marathon, in support of Jenny Crain and the Make it Happen Fund.

Robin Gohsman, a business owner from Nashotah, organized both efforts, also motivated more by LifeStrider's charitable cause than setting a Guinness Book record.

"They do incredibly magical work," Gohsman said.

While half the distance, the half marathon effort in the Trailbreaker proved to be exponentially more difficult, with 40 more people and all that added rope.

The line of runners stretched for more than 100 yards and defied any sort of steady pace. Led by Waukesha Mayor Jeff Scrima, the group moved and stopped, moved and stopped, for nearly three hours, and placed 476th to 578th.

The team raised more than $30,000 for LifeStriders and another $2,000 to support Crain, an Olympic-caliber runner who suffered severe injuries when hit by a car in August 2007.

Much like Knowles, Scrima said the Guinness record was secondary to the larger purpose.

"Guinness never crossed my mind," he said. "I came to know the organization through the fund-raising event. It was rewarding to see the results of what they do in person, through the mother who ran and the child."

Matthew Knowles joined the group at the finish line, a chaotic scene that typically would make him distressed and agitated. Instead, he beamed, waved and cheered, much as he does atop a horse at LifeStriders.

"Usually, he has the biggest smile on his face," Sarah Knowles said. "He claps his hands and makes these little clicking noises. Sometimes he'll even be giggling and laughing. You can tell from his body language and his expressions that he is happy."

It's a joy that will never be recorded in a book of records; only in a mother's heart.

See images of the LifeStriders centipede here.