physical exertion vs exercising

physical exertion and exercising both are nouns.

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

As nouns, physical exertion and exercising are synonyms defined as:

physical exertion and exercising: the activity of exerting your muscles in various ways to keep fit

Other synonyms of physical exertion include exercise, physical exercise, workout.

physical exertion (noun)	exercising (noun)
the activity of exerting your muscles in various ways to keep fit	the activity of exerting your muscles in various ways to keep fit