Ryan Phillippe is living proof that exercise can be really, really bad for you -- dude just broke his foot while running on a treadmill.
We're told Phllippe was running on his treadmill barefooted when he suffered a stress fracture on his left foot.
Phllippe -- pictured above in Los Angeles Thursday night -- has been sportin' a hip and trendy walking cast ever since.
12/19/2009 4:07 AM PST BY TMZ STAFF
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