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Marcela Perea, owner and personal trainer for CrossFit 100 in Glendale, Wi., demonstrates the banded rotation exercise. This is great for core training and stabilization. 5 Questions with LeRoy Butler ...
(CNN) — Deep inside Earth is a solid metal ball that rotates independently of our spinning planet, like a top whirling around inside a bigger top, shrouded in mystery. This inner core has intrigued ...