This:
Here is a good video of the race
https://www.youtube.com/watch?v=eTUadSnzqYk
Go to 5:50 in. Simpson is running with her normal stride. At 5:56, when Rowbury is about to pass her, Simpson's left arm goes much wider than her normal stride. Simpson's arm clearly causes the contact.
Not sure if it is a DQ worthy offense, but for those of you who are saying Rowbury caused the fall, you are flat out blind
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Simpson clearly caused the contact. You can't cause contact from the front - yes - but you can from the side, which is where Jenny was in relation to Rowbury at 5:56 in the video. Her left arm goes out - why? To impede Rowbury.