A “mixed race marriage” usually does not involve running, but there are jokes. “I happen to know that at least one anti-spammer who frequents NANAE is in a mixed-race marriage (...) They run both the 3K and marathons?” was posted on the newsgroup news.admin.net-abuse.email on August 27, 2004.
 
“Dad was a marathon runner when he met my mum, who was a sprinter. They’ve been married 33 years - who says mixed race marriages don’t work?” was posted on Twitter by Jason on August 25, 2010. “If a 100 yd dash champion weds a marathon runner, is it a mixed race marriage? #rimshot” was posted on Twitter by Jazz Shaw on December 30, 2013.
   
“I come from mixed race parents. My dad was a hurdler and my mom a sprinter” is a similar joke.
         
   
Google Groups: news.admin.net-abuse.email
affordablehost tos
Allis
8/27/04
(...) 
> I happen to know that at least one anti-spammer who frequents NANAE is in a mixed-race marriage
 
They run both the 3K and marathons?
Wow.
   
Twitter
Jason
@NickMotown
Dad was a marathon runner when he met my mum, who was a sprinter. They’ve been married 33 years - who says mixed race marriages don’t work?
3:28 AM - 25 Aug 2010
   
Twitter
Jason
@NickMotown
Marathon star Paula Radcliffe wed 1500m runner Gary Lough 11 yrs ago & they’re still together. And some say mixed race marriages don’t work.
5:02 AM - 16 Feb 2011
 
Twitter
cyclerunner
@cyclerunner
I am the child of a mixed-race marriage. My mother was a marathon runner and my dad a sprinter.
5:42 AM - 3 May 2012
   
Twitter
Sheeda Mauchi
@PUNderbeard
My former marathon runner neighbour celebrated golden anniversary with his 100m sprint medalist wife…proving mixed race marriages work…
9:14 PM - 20 Sep 2013
 
Twitter
Jazz Shaw
@JazzShaw
If a 100 yd dash champion weds a marathon runner, is it a mixed race marriage? #rimshot
7:51 PM - 30 Dec 2013
 
Reddit—Dad Jokes
My mum was a 100M runner and my dad was a marathon runner. (self.dadjokes)
submitted September 29, 2018 by TheSquidgster
Sadly, no one approved of their relationship.
In the old days no one like mixed race marriages.