Reese Upside Down without Jake?

9/14/2007 12:44 PM PDT BY TMZ STAFF
Amid rumors that her alleged romance with Jake Gyllenhaal is on the fritz, Reese Witherspoon was spotted in a Santa Monica park going heels over head for a tree. Walk the trunk!

Reese flipped while doing her aerobics with a trainer. Who will she flip for next?