WordNet sense 1 (consisting of tendons or resembling a tendon):

tendinous

WordNet sense 2 ((of meat) full of sinews; especially impossible to chew):

fibrous, stringy, unchewable

WordNet sense 3 (resistant to cutting or chewing):

tough

WordNet sense 4 ((of a person) possessing physical strength and weight; rugged and powerful):

brawny, hefty, muscular, powerful

WordNet sense 5 (having strength or power greater than average or expected):

strong