OKLAHOMA CITY, OKLAHOMA -- They train at Lake Overholser.
John Nelson and his daughter Nicole will run the half-marathon at the 2014 Oklahoma City Memorial Marathon.
Like any other long distance runners, they put one foot in front of the other, through cold or heat, and through pain.
John speaks of another athlete in the Nelson family, "I can't remember a time when he did not enjoy this run."
They raced together many times before.
Fellow runners and race spectators would recognize John better if he were pushing his son Chris in his specially constructed racing chair.
Father and son started running together just before the very first Memorial Marathon.
They ran in almost every one, and lots of others too.
The Nelsons cherish a photograph taken in October of 2013, less than a week before he passed away.
In a halting voice, still choked with emotion, John says, "Our biggest blessing is..."
He takes a long pause, "he was a happy boy."
Memories and loss sometime bubble to the surface in poignant ways.
After an accident at age 3, Chris couldn't speak or move, but close family insist he loved life.
So as April, 2014 approached and the weather warmed up, the question of whether to run in the Memorial Marathon came up too.
Both John and Nicole answered it quickly.
"The first instinct is to say 'I'm done," says Nicole, "But then you think that would be an insult because it was so much a part of him and what he loved."
Speaking of this year's race, John says, "I think it helps to kind of put it behind you. Try to keep on track."
Chris had several bells attached to his racing chair so other runners wouldn't get tangled with the wheels.
John will wear one of those bells on his shoe, running through the ache in his legs and the ache in his heart.
Like so many of his fellow runners, he will run to remember, to celebrate, and to ring on.
For more information on the Memorial Marathon go to http://www.okcmarathon.com