On Food and Cooking

Steer anatomy and cuts of beef. The shoulder,
arm, and leg do most of the work of
supporting the animal. They therefore contain
a large proportion of reinforcing connective
tissue, are tough, and best cooked thoroughly
for an hour or more to dissolve the
connective-tissue collagen into gelatin. The
rib, short loin, and sirloin do less work, are
generally the tenderest cuts, and are tender
even when cooked briefly to a medium
doneness.
Red Muscle Fibers Red muscle fibers are
used for prolonged efforts. They are fueled
primarily by fat, whose metabolism
absolutely requires oxygen, and obtain both