Art Meyer was nearly finished with the swimming portion of the Rochester triathlon Sunday when he noticed the swimmer ahead of him floundering in Foster-Arend Lake.

"I don't know if he pushed himself too hard or what," Meyer said. "He was flailing. I asked if he needed help but he couldn't really talk."

Meyer yelled for help, but the 56-year-old competitor died a few minutes later while emergency responders tried to get his heart beating again.

Police have not released the name of the victim. A spokesman for the Olmsted County Sheriff's Office said the man had no pulse and was not breathing when he was pulled to shore in a rescue boat.

Medical experts said the incident is a reminder of the risks that come with the demanding sport. Since 1985, 117 athletes have died while competing in triathlons across the U.S., including one previous incident in Minnesota, according to a 2016 report from the Minneapolis Heart Institute Foundation. Three-quarters of those victims died in the swimming portion of the event, which also includes bicycling and running.

"We don't know exactly what happened here today, but the swimming part of a triathlon is very difficult to prepare for," said Dr. Kevin Harris, who led the research effort. "I don't think you can adequately prepare for it by just swimming in a pool. I think it would be a good idea to train in the same sort of conditions you experience in the race, with other swimmers around you."

Harris said middle-aged athletes should undergo a cardiovascular exam before entering a triathlon, especially if they are at risk of heart disease. In reviewing the 117 deaths, Harris found that the average victim was male and about 50 years old. Many had undiagnosed heart problems.

On Sunday, the first event for about 230 triathletes was a quarter-mile swim.

Meyer, 52, said he had not trained for the swim and was struggling to reach the finish line when he noticed the man in trouble. He said he tried pulling him to the shore.

"He couldn't support his own weight," said Meyer.

A boat came to rescue the man and responders were giving him CPR by the time Meyer reached shore. Meyer continued his race, but stopped back to check on the other man after finishing the 10-mile bike ride. By that time, the man he tried to rescue was dead.

"I just thought, 'Do I finish? Do I go home?' " Meyer said. "Who cares anymore? Well, I like to run. It helps me process things. So I finished the race."

In 2002, a 36-year-old man died while swimming the first leg of the Timberman Triathlon in Grand Rapids, Minn.

Staff writer Pat Pheifer contributed to this report.