He was not a serious runner then, but a teacher told him he had talent.
The race is open to serious, and less competitive, runners of all ages.
Even serious runners are doing less running, and adding muscle weight through swimming, gym work and other activities.
He could tell the serious runners from the weekend warriors.
As it stands, few serious runners are likely to take up the challenge to turn it on.
If you're a serious runner, you may get the occasional black toenail.
Pettie has a running pedigree - he used to run cross-country at school and his father was a serious runner.
"All serious runners keep running until they drop."
It is often used by serious runners as a means of active recovery during interval training.