28-year-old Cierre Wood -- a former star running back at Notre Dame -- appeared in a Las Vegas courtroom Tuesday in the death of his girlfriend's daughter La-Rayah Davis.
Davis died on April 9th -- and prosecutors say it's because Wood forced her to complete a hellacious workout routine unsuited for a 5-year-old.
Officials say Wood claimed Davis had behavior issues -- he also described her as "chunky" -- so to punish her, Wood would force her to run wind sprints and do sit ups and wall squats inside their apartment.
Officials say Wood admitted David couldn't complete a second round of sit ups on April 9th -- and flailed backwards, smacking the back of her head against the floor.