Martin was born with spina bifida, a birth defect involving the spinal cord and has been a frequent patient at Children's, enduring multiple surgeries and other treatments. Martin inspired Phillips, who recognized that a 26.2 mile run was nothing compared with what the child faced every day.

On race day, Martin would wait for Phillips at the top of Boylston Street. “What took you so long?” became his refrain as Phillips carried him on his back, and later pushed him in a wheelchair to the finish line.

Martin has kept each finishing medal, declaring they had won the race. When he turned 18, Martin completed the race himself in the wheelchair division, finishing the race in 2014 and 2015. This year, medical issues have interfered with his training schedule, so he didn't enter the race. But he's already planning for 2017.

Phillips runs about six marathons a year, including races in Vermont, New York, Miami, and, of course, Boston.

As he approached his 100th marathon, Phillips revealed his not-so-secret motivation.

“Every year at the finish line, Andy and I renewed our commitment to each other and the race. I would have stopped long ago if it hadn't been for Andy,” Phillips said.

Phillips already has his eye on a new goal. In only eight years, at the age of 76, he plans to run his 25th Boston Marathon. And, no doubt, Andy Martin will be there to cheer him on to the finish line.