That's because, he says, growing up in Southern Sudan, he used to run for his life. During the country's decadeslong civil war between the Northern government and Southern rebels, Marial, 28, saw many family members die at the hands of federal forces. He was also kidnapped twice before a 2005 peace deal ended the war in which more than 1.5 million people died.
Last July, South Sudan successfully seceded from Sudan. Now Marial is set to run against more than 100 other participants in Sunday's Olympic marathon — but not under the newly independent nation's colors. The landlocked, oil-rich East African country missed out on being part of the games because there was little time to complete the lengthy process to be recognized by the International Olympic Committee.
For South Sudan Sports Minister Cirino Hiteng Ofuho, not being able to fly the country's new flag over the Olympic Stadium is a bitter pill to swallow. After all, he said, the nation was very quickly welcomed into the United Nations, the African Union, the powerful international soccer body FIFA and the African soccer organization. He says that the delay in being recognized by the IOC is "disappointing."
"The process takes two years, and we are just one year independent now," he told The Root. "And so that already has hampered our efforts to participate in these Olympics, even if we had prepared a few athletes in the Paralympic Games in basketball."
The IOC suggested that Marial run for Sudan, but he refused. Instead he chose to compete as an independent — one of four athletes chosen by the IOC — under the Olympic flag. Though Marial fled Sudan at 15 and attended Iowa State University after arriving in the U.S. as a refugee in 2001, he hasn't yet received U.S. citizenship, so he can't compete as an American.
"For me it means a lot to glorify the people who died for their freedom and people who lost their lives, including 28 members of my family and relatives," he told Reuters. "Their spirit is what allows me to get up every single day, put on my shoes and train to honor them."
East Timor faced a similar situation when it voted for independence from Indonesia in August 1999. Four athletes from the small island nation competed as "individual Olympic athletes" at the 2000 Games in Sydney.
When they entered the stadium, dancing in sheer joy, the entire stadium gave them a standing ovation. In a similar way, South Sudan is already making its mark on the games.
Although the nation doesn't have a team at London 2012, it doesn't lack for talent. Marial is one of three stellar South Sudanese athletes competing in the games — all under different flags. Basketballer Luol Deng, who plays for the Chicago Bulls, leads the British basketball team. And the U.S. track-and-field team's flag bearer, Lopez Lomong, is one of Sudan's famous Lost Boys — a group of some 20,000 children displaced during the last civil war.
And, Ofuho says, the world should watch out come Brazil 2016. He says that South Sudan is working to improve its athletic facilities after decades of conflict and neglect. He expects the nation to shine in athletics and basketball as well as other sports during the Rio Games. "Even we have games like wrestling and javelin; all of these games we're going to participate in," he said.
While South Sudanese nationals will be closely watching from around the world, Marial has said that he hopes his parents, whom he hasn't seen since 1993, will get to visit a nearby town or city where there is a television. There are reports that they may have to walk more than 30 miles to watch him.
London resident and South Sudanese ex-patriot Helen Mulla, 37, says that she hopes her three children will watch their mother's nation with pride. "I think … in time we will get enough people to represent South Sudan at the next Olympics," Mulla said. "When we do finally get going, there will be the Republic of South Sudan in the Olympics, and I am so proud."
Anita Powell is a Johannesburg-based journalist who has covered Africa for five years and previously covered Iraq and Afghanistan. She is in London following the Olympic Games and her favorite sport, boxing. Follow her on Twitter.