Ron Hill, 78, a three-time Olympian for Great Britain, ended his running streak on Sunday, January 29.

The streak—during which Hill ran at least one mile every day—had stood for 52 years, 39 days. It was the longest known running streak in history.

In a statement released by Streak Runners International, Hill, who lives in Hyde, a town a few miles east of Manchester, wrote: “I have been having heart problems and have been waiting for some time now to have the problem diagnosed and hopefully rectified.”

On January 28, Hill wrote, he ran his last mile of the streak.

“After less than 400 metres my heart started to hurt and over the last 800 metres the problem got worse and worse,” the statement reads. “I thought I might I die but just made it to 1 mile in 16 minutes and 34 seconds. There was no other option but to stop. I owed that to my wife, family and friends plus myself.”

In 2014, when Hill’s streak hit 50 years, he told Runner’s World, “I hope to live to 100 years and still be running.” Over the first 50 years of the streak, he averaged more than seven miles per day, but he had been running less, about 25 miles per week, in his mid 70s.

The streak was only one small accomplishment in Hill’s career. He competed in the Olympics in 1964, 1968, and 1972. In fact, his disappointment in his performance in the 10,000 meters and marathon at the 1964 Games in Tokyo was what inspired him to begin the streak.

Hill won the Boston Marathon in 1970 in 2:10:30, what was then the course record. He was the second person to break 2:10 in the marathon, running a personal best of 2:09:28. He held world records for 10 miles, 15 miles, and 25K on the roads.

According to SRI, Jon Sutherland, 66, of West Hills, California, now holds the longest streak for consecutive days running, at 47 years and 8 months. He said he was saddened by the end of Hill’s streak.

“I’m a fan from afar,” Sutherland said of Hill. “He was an incredible pioneer, one of the most important figures in the evolution of running.” Sutherland says that Hill had a four-year streak going before the 52-year string of runs began.

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Sutherland is not sure whether he will be able to continue running to approach the mark that Hill set. “I had my worst year ever in 2016,” Sutherland said. Plagued by nagging injuries, he ran 1,066 miles in 2016, and on 20 days, he ran the one-mile minimum required to maintain his streak. (He usually runs three miles each day at between nine- and 10-minute-mile pace.)

“[The streak] doesn’t drive me that much,” he said. “I was more driven by competition when I was younger. I do it because I enjoy it. I try not to think about it.”

Jim Pearson, 72, of Marysville, Washington, is second on the current streak list (46 years, 11 months).

Stephen De Boer, 62, of Rochester, Minnesota, is currently in third place at 45 years, 7 months. In an email to Runner’s World, he said he is not motivated to try to set the longest streak, even though he is younger than those ahead of him on the list.

“It is an internal thing to run every day, no matter who is ahead of or behind me,” he wrote.

This article originally appeared on RunnersWorld.com.