Depending the venue and lay-out around the stadia, but if you just hang out between morning and evening sessions you can often bump into some significant athletes and coaches. At Gothenburg I bumped into the Jamaican women’s sprinters and they were really playful, cracking jokes on the walkby.
I also saw Bertland Cameron out on the street and was trying to catch up to them, saying he had the best job in the world now as masseur for Merlene. lol. He said it with such a goofy look on his happy face I’m still laughing now when I recall.
One other thing worth doing is to case the periphery of the stadium and find some little bar and restaurant slightly out of the way where you can chill between sessions if going back to your hotel for a rest is too inconvenient. Make friends with the people who work there, give them a souveneer from your country of whatever and they might be happy for you to use their toilet even when you’re not dining there. Finding a little place for respite can be valuable. You do need to eat something healthy occasionally if only to keep your strength up and you may find prices inside the “official area” somewhat rich.