The next day, he caught a flight home.
“I don’t like missing work because of my running,” said Mr. Sim, 44, who works at Daewoo Shipbuilding and Marine Engineering on this island off the southern port of Busan.
Massanutten race officials and runners recall him as a “total unknown” who spoke no English except “Water, water!” and “Thank you!” But Mr. Sim has become something of a legend among South Korea’s amateur marathoners, whose population has exploded in the past decade. He has been nicknamed the Korean Forrest Gump, after the movie character who runs across America.
Mr. Sim got his start running after six years of nine-hour workdays inside the ships, breathing chemicals and dust through a face mask. His respiratory system was so weak that in 1993, doctors recommended surgery to help him breathe. “Because of breathing difficulties, I always kept my mouth open, looking like an idiot,” he said. He also lost most of his sense of smell. (On race days, he asks fellow runners to smell his lunch box to check if any food has gone bad.)
But Mr. Sim, a determined man if there ever was one, refused an operation. “Instead of surgery, I decided to run,” he said. “I decided that, even if I died, I would die running, with my lungs full of air.” His lung capacity, measured in 2003 at 69.5 percent, now registers as normal, he said.
Despite still working five or six days a week at the shipyard — he now repairs welding machines — he runs three marathons a month; in spring and fall, as many as seven. In all, Mr. Sim has run 210 amateur marathons since 1995, and finished all but three of them under three hours.
With his personal record of 2:29:11, he cannot compete with professionals — the current men’s record, subject to ratification by the International Association of Athletics Federations, is 2:03:23, by Wilson Kipsang of Kenya. But Mr. Sim’s 90 victories are widely considered South Korea’s amateur best, although there is no official agency compiling amateur data.
He sometimes runs a marathon on Saturday and again on Sunday, and has won six such back-to-back marathons. He excels in so-called ultrarunning endurance races, typically double the length or several times longer than the 26.2-mile marathon and often conducted on mountain trails. He has run more than 30 such races at home and abroad and won 10 of them. “I am happier running than walking,” he said in an interview at his home.
MR. SIM grew up in an isolated village near Mungyeong in central South Korea, one of the country’s most mountainous regions, at a time when villagers were still collecting mountain herbs and hunting wild animals for food. He had to walk two miles to school or to the nearest candy store, and recalls chasing rabbits and pheasants over the steep slopes. (This early experience helps him in mountain trail races. He said he felt comfortable in the woods.)
Nevertheless, he said, he was never good at running in his school years. “I was one of the shortest kids in school, and they seldom let me compete in the races, and even when I did, I never finished even third,” he said.
Now, his golden business card identifies him as “golden legs” and “iron worker.” Among his shipyard colleagues, his nickname is “the iron man.”
Beyond his personal exploits, though, Mr. Sim’s hero image owes something to the special place that the marathon holds in South Korea.
South Koreans still consider the medal the marathoner Sohn Kee-chung won at the 1936 Berlin Olympics to be the first Korean Olympic gold, though Mr. Sohn ran as a member of the team from Japan, Korea’s colonial ruler at the time. A photo of Mr. Sohn from the medal ceremony — holding a leafy branch to hide the Japanese flag on his tracksuit — is one of the most celebrated images of Korean national pride.
Although South Koreans craved another marathon gold, the sport attracted few participants among ordinary people. That began slowly changing after the South Korean runner Hwang Young-cho won the marathon in the 1992 Barcelona Olympics. But it was the Asian financial crisis of the late 1990s that helped fuel the marathon boom. With their once-proud economy crippled and jobs evaporating, many middle-age South Koreans took to long-distance running and mountain climbing, embracing the physical and psychological challenges of endurance sports.
When Mr. Sim ran his first marathon in 1995, it was the country’s first open for amateur runners. It took him 14 years to complete 100 “sub-three-hour” marathons, a first for a South Korean. But with racing events proliferating, he needed only four more years to run his next 100. By then there were more than 120 marathon competitions a year in South Korea, in addition to hundreds of half-marathons and shorter races. The spread of urban health clubs, with their treadmills, helped spur the running trend.
“At first, there were no marathon competitions ordinary people like me could enter,” Mr. Sim said. “Now there are so many you can’t run them all, especially when you have a full-time job, as I do.”
He also saves money and vacation days to compete in ultrarunning competitions abroad. He has won them in Japan and Singapore, and narrowly missed placing among the top 10 in the 100-mile Western States Endurance Run in the Sierra Nevada in California in 2007 and 2011. He has fared less well in European alpine races, in which he has suffered hypothermia and sometimes had to quit before the finish line, as he did in the 200-mileTor des Géants race in Italy in September.
MR. SIM’S fame has attracted corporate sponsors, who provide him with shoes and other running gear and energy supplements. In return, he has appeared in their magazine advertisements and carries their logos on his running shirt.
He follows a spartan routine. Six days a week, he gets up at 5 a.m. and starts his day with an apple and 50 chin-ups. He runs 12 to 15 miles a day on a treadmill or on the road. Some days, on his way home from work, he runs mountain trails that overlook the cranes and dry docks of Geoje, the center of South Korean shipbuilding.
He said running left his feet perpetually bruised, and he has lost hundreds of toenails. His wife complains that he often misses Sunday church services because of marathons. His 15-year-old son, Young-bo, said he felt proud when his friends marveled at the trophies covering the family’s living room wall, but he, too, wishes his father would slow down a bit.
Mr. Sim has no such plans.
“I never finished first in anything until I started running,” he said. “Only death will make me stop running.”