From high school football on up to the NFL, offensive linemen are taught that if their assignment gets his hands up, they have to hammer him in the stomach or diaphragm, just below the pads, dropping his hands. The weapon of choice is the palm heel strike - called a ‘shotei’ in the Japanese fighting arts - and it’s identical to the technique used in football, including the NFL. I’m a smaller guy, and I used it to easily break four inches of pine at a time - the 300+ lb behemoths can do a lot of damage with it, very fast.
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