Consider a martial artist

capable of striking with 190 joules (J) of energy. A typical
human hand is about 6 inches long including the fingers and 4 inches across, which
means that a strike with the entire hand disperses those 190 J over 24 square inches,
about 7.92 J per square inch. If, however, the karateka strikes with only the fleshy part
of the palm, about 2 inches across and 1.5 inches long, the 190 J will be dispersed
over only 3 square inches. That strike will deliver about 63.3 J per square inch,
inflicting many times the amount of damage the whole hand could—the same amount
of energy dispersed over a smaller area delivers more energy per unit area.