physical exertion vs exertion

physical exertion and exertion both are nouns.

Word	Noun	Adjective	Verb	Adverb
physical exertion	Yes	No	No	No
exertion	Yes	No	No	No

As nouns, exertion is a hypernym of physical exertion; that is, exertion is a word with a broader meaning than physical exertion:

physical exertion: the activity of exerting your muscles in various ways to keep fit
exertion: use of physical or mental energy; hard work

Other hypernyms of physical exertion include effort, elbow grease, sweat, travail.

physical exertion (noun)	exertion (noun)
the activity of exerting your muscles in various ways to keep fit	use of physical or mental energy; hard work