I updated the link, it should work now
Marion Jones is in there indeed and I also recognised Gail Devers and Inger Miller. A bit of research makes me think that was a scene from the 1997 Worlds in Athens so you may want to look for any footage on YT based on it.
I remember seeing it on TV as kid and I was amazed, they already looked so ripped during the race but I wasn't expecting them to actually flex. There was about 20 seconds of them flexing for the camera with different angles, it was the team that had Marion Jones in it.
Here is a GIF of it:
https://jmp.sh/s/cUCSeNMg1EQaJDtWW6hW