Running phenom Sam Ruthe set another middle distance record - and there's belief it could go deeper than good genetics.

The 16-year-old broke Sir John Walker's overall national mile mark set at Oslo in 1982 at an indoor meet in Boston.

Ruthe's grandfather, Trevor Wright, is also a skilled runner, but he says genetics only contribute to a small part of the teen's success.

"I put it down to dedication, talent and a good coach and a good manager...definitely dedicated."

LISTEN ABOVE