If you are thinking, well, why do I even have slaves if I can't force them to help me get into the Guinness Book of World Records, you are missing the point entirely and are also an extremely bad human being.
If you are thinking, what better way to respond to allegations of poor working conditions than to force indentured servants to run a marathon in the desert, you must be Qatar.
Qatar, for those of you who don't know, is not the newest member of The Avengers but rather a tiny emirate in the Persian Gulf that had the foresight to park itself over a place where oil would one day be found, and it is therefore one of the absolute monarchies that we are pals with. Although most countries in that area are shining examples of progressive humanism, Qatar has been repeatedly criticized for its treatment of workers who have migrated there to build stuff for the 2022 World Cup.
An investigation by The Guardian found that many of the laborers were being forced to work long hours in 120-degree heat, without enough food and water. In the summer of 2013, a worker died almost every day, half from heart attacks. (2014 numbers were almost as bad.) They were often not paid, required to live in "filthy hostels," and their employers took away their passports so they could not leave. The investigation concluded that the conditions amounted to "modern-day slavery." The committee that's running Qatar's World Cup effort said it was "deeply concerned" about the allegations and that it had been informed that government authorities were looking into the matter.
I'm gonna speculate that no radical changes were made, based on the report that last month hundreds if not thousands of migrant workers were bused in and forced to run a half-marathon in Doha (let's be honest: in the desert) because the organizers were trying to break the world record for most participants. A source said he had "observed hundreds of men who appeared to be laborers, wearing jeans, flip-flops or running barefoot." Some tried to leave, said another, "but were turned back and were yelled at that they need to stay and cross the line."
According to the race's official site, the Qatar Mega Marathon (mega-half-marathon, that is), was intended as a public-relations effort, representing "a decisive response to the campaign waged by the sector of envious haters on the success of Qatar to host the 2022 FIFA World Cup, and to their false allegations of persecution of workers and residents in our beloved country." That does not appear to have been successful, nor did they even get close to breaking the record. On the other hand, the site also says that the race was partly intended to "emphasize the importance of the participation of people with special needs in social events," and I guess you could say it did that if you define "special needs" to include shorts and running shoes.
So far as I can tell, no one (enslaved or not) died during the race. Take that, envious haters.