A gorilla's upper body is six times stronger than a human's, and the muscles in a gorilla's arms are larger than those in its legs. They use their arms to move foliage, gather food and defend themselves. Gorillas also need strong arms because they typically walk on all four limbs.

Gorillas are the largest primates. Depending upon the species, adult males weigh between 374 and 484 pounds, while females tip the scales at 160 to 215 pounds. Their arms are significantly longer than their legs, while their stomachs are bigger than their chests. This isn't due to excess fat. Gorillas have large intestines in order to digest quantities of plant life. Gorillas have huge domed heads that provide support for the large muscles needed to chew all that vegetation.