subconcussive

The Ivy League adopted groundbreaking new rules for the 2011 football season intended to lower the risk of concussion and the number subconcussive hits, including reducing to two the number of full-contact, in-season practices allowed per week. New research suggests that such repeated hits may cause more brain damage than blows resulting in diagnosed concussions.  

The conclusion that chronic traumatic encephalopathy (CTE) is caused by concussions and repetitive subconcussive brain trauma is scientifically premature, say an increasing number of researchers.