The answer is most likely different for everyone.
An article posted on BBC Sport’s Web site asks the question many of us ponder when we see a solitary runner: Just what is that person thinking about?
Celebrated Japanese author Huraki Murakami may have put the answer to this question best when he wrote, “I run in a void, or maybe I should put it the other way: I run in order to acquire a void.”
Many people use running to help them recover from tragic events. At this past weekend’s ING New York City Marathon a group of family members who lost loved ones in the 9/11 terrorist attacks ran to commemorate their departed family member. One of these runners was Kiki Homer who’s brother died on that tragic day. He was aboard Flight 93.
“When I’m out there running on Sunday, I know there are going to be moments when I won’t want to continue but I’ll think about my teammates and the 40 passengers on board,” she said.
Homer took part in the first race in 2002, a year after the tragedy.
For More: BBC