Portuguese runner Adriele Silva gestures during the Great Wall Marathon at the Huangyaguan section of the Great Wall of China, in Jixian of Tianjin, China May 19, 2018. (Photo by Jason Lee/Reuters)

Centenarian Sikh runner Fauja Singh poses for pictures after being the first person to officially enter for next year's Edinburgh Marathon on September 1, 2011 in Edinburgh, Scotland. A world record holder, aged 100, Fajua Singh has run seven marathons, all after his 89th birthday. He officially opened the entry process by signing up for his last ever 26 mile event in Edinburgh. (Photo by Jeff J Mitchell/Getty Images)

Costumed competitors run during the Marathon International du Beaujolais race near in the gardens at the castle of Pizay, November 22, 2014. Its 10th edition gathered more than 10,000 runners from 60 countries making their way on small roads, around and through the castles and vineyards, in the Beaujolais region. (Photo by Robert Pratta/Reuters)

Bristol Zoo's baby gorilla Kukena holds onto his mother's arm as he ventures out of his enclosure at Bristol Zoo's Gorilla Island on May 4, 2012 in Bristol, England. The seven-month-old western lowland gorilla is starting to find his feet as he learns to walk having been born at the zoo in September. Kukena joins a family of gorillas at the zoo that are part of an international conservation breeding programme for the western lowland gorilla, which is a critically endangered species. (Photo by Matt Cardy)

Competitors dressed in a gorilla outfits prepare ahead of the Great Gorilla Run on September 24, 2011 in London, England. Hundreds of people dressed in gorrilla suits participated in the 7 km run around the City of London which is hoped will raise £400,000 GBP, anabling funding for projects dedicated to the protection and preservation of Gorillas. (Photo by Dan Kitwood/Getty Images)

Runners sleep before competing in the 2016 New York City Marathon in the Manhattan borough of New York City, NY, U.S. November 6, 2016. (Photo by Eduardo Munoz/Reuters)

Actress Andrea Barber crosses the finish line at the Rock 'n' Roll Los Angeles Halloween Half-Marathon and 5K benefitting the ASPCA, or American Society for the Prevention of Cruelty to Animals on October 26, 2014 in Los Angeles, California. (Photo by Rich Polk/Getty Images for CGI)

Abigail Crouse lifts her Thor hammer high after running through Sleeping Beauty's Castle during the Avengers Super Heroes Half Marathon in and around the Disney Parks in Anaheim, California November 16, 2014. Walt Disney Co has moved aggressively into the race business, attracting tens of thousands of runners every year to its marathons, half-marathons and family-friendly races. (Photo by Eugene Garcia/Reuters)