According to a study in 2010 by Cindy Bir a Biomedical Engineer at Wayne State University in Detroit, a quick, sharp blow that delivers about 3,300 Newtons of force has a 25 percent chance of cracking an average individual’s rib. And it takes more force, approximately 4,000 Newtons, to fracture the femur (thighbone).
Bone is extremely strong — ounce for ounce, bone is stronger than steel, since a bar of steel of similar size would weigh four or five times as much. A cubic inch of bone can in theory bear a load of 19,000 lbs. (8,626 kg) or more, about the weight of five standard pickup trucks, making it around four times as strong as concrete. Still, whether or not bone truly withstands such loads depends greatly on how quickly force is delivered.
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