Tendons are, essentially, elastic cords stretched between two fixed ends. $$As $$such$,$ they can support standing waves. A woman has a $19$ cmcm $-$long Achilles tendon$-$connecting the heel to a muscle in the calf $-$ with a cross $-$ section area of $94$ mm$2$mm$2.$ The density of tendon tissue is $1100$ kg$/$m$3$kg$/$m$3.$