pull-up vs arm exercise

pull-up and arm exercise both are nouns.

Word	Noun	Adjective	Verb	Adverb
pull-up	Yes	No	No	No
arm exercise	Yes	No	No	No

As nouns, arm exercise is a hypernym of pull-up; that is, arm exercise is a word with a broader meaning than pull-up:

pull-up: an arm exercise performed by pulling yourself up on a horizontal bar until your chin is level with the bar
arm exercise: exercise designed to strengthen the arm muscles

pull-up (noun)	arm exercise (noun)
an arm exercise performed by pulling yourself up on a horizontal bar until your chin is level with the bar	exercise designed to strengthen the arm muscles
a roadside cafe especially for lorry drivers