In an effort to better understand the effects long-distance running has on the heart, a number of runners will wear portable heart monitors during a marathon this month in Amherstburg, Ont., west of Windsor.

Participants in this year's Run For Heroes Marathon will wear portable electro-cardiogram devices as they run the race.

The monitoring device is called a cardiphone. It is a wireless device that combines heart monitoring and cellphone technology.

Experts at the Windsor Cardiac Centre will monitor their every heartbeat in real time, 40 kms away in Windsor. Dr. Wadea Tarhuni said the device will flag if runners are in danger.

"We can assure them that every heart beat will be counted and every heart beat will be followed through satellite technology at our centre," Tarhuni said. "We can assure them that if there's any abnormalities we're able to intervene at the right time."

Cardiologists say marathon runners, triathletes and long-distance cyclists could be doing long-term damage to their hearts.

The June issue of the Mayo Clinic Proceedings includes a review of how excessive endurance exercise is thought to cause damage to the heart.

The study's authors say that based on both animal and human data, the cardiovascular benefits of vigorous aerobic exercise build up over about one hour, "beyond which further exertion produces diminishing returns and may even cause adverse cardiovascular event effects in some individuals."

After people reach their mid-40s, long and intense exercise can cause scarring and fibrosis in the heart, said lead author Dr. James O'Keefe of Saint Luke's Hospital in Kansas City, Mo.

Data to be analyzed

Although the device in Amherstburg is being used as a demonstration, doctors say the data will be analyzed in an effort to help save lives. A specialist with the Windsor Cardiac Centre will study the data collected at the race on Sept. 23.

Dr. Davinder Jassal, a principal investigator of the cardiovascular imaging laboratory at St. Boniface Hospital and Research Centre and associate professor of Cardiology at the University of Manitoba, is also studying the hearts of marathon runners.

"Some studies have been showing scar, other studies like ours have shown no permanent damage to the heart, so the jury is still out there in terms of whether there's conclusive evidence that scar occurs in marathon runners," Jassal said.

Chris Uszynski is a runner and organized the race in Amherstburg.

He said some long-distance runners can have unknown dangerous heart conditions.

Uszynski is still haunted by the death of a man running beside him during the 2009 Detroit Marathon.

"He just dropped like a stone - a young guy, 26 or 27 years old," Uszynski said.

Three people in total died during that event.

"Anytime that happens in a race, any racer that's around him, I mean, it leaves a mark. It really does," Uszynski said.

Jodi Bray has been running for most of her life. She plans to participate in the marathon and wants to wear the machine.

"I think it's a great idea and to be honest I volunteered for it for the research to assist the physician," Bray said.

With files from CBC News