muscle vs heftiness

muscle and heftiness both are nouns.

Word	Noun	Adjective	Verb	Adverb
muscle	Yes	No	Yes	No
heftiness	Yes	No	No	No

As nouns, muscle and heftiness are synonyms defined as:

Other synonyms of muscle include brawn, brawniness, muscularity, sinew.

muscle (noun)	heftiness (noun)
possessing muscular strength	possessing muscular strength
authority or power or force (especially when used in a coercive way)	the property of being large in mass
one of the contractile organs of the body
animal tissue consisting predominantly of contractile cells
a bully employed as a thug or bodyguard

muscle (verb)	heftiness (verb)
make one's way by force