It took a Puerto Rican national record of 48.42 from Culson to beat Jamaican Isa Phillips ( 48.79 ) in the men 's 400m Hurdles .
A Puerto Rican national record of 48.42 is a world leading mark .
It took a Puerto Rican national record of 48.42 , a world leading mark , from Culson to beat Jamaican Isa Phillips ( 48.79 ) in the men 's 400m Hurdles .