One prone to use arms in this exercise? (5-2)

I believe the answer is:

press-up

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'this exercise?' is the definition.
(I've seen this before)

I don't understand the remainder of the clue.

(Other definitions for press-up that I've seen before include "Form of arm exercise" , "PE exercise" , "Gymnastic floor exercise" , "Arm exercise while lying face down" , "Face-to-the-floor exercise" .)

I've seen this clue in The Sun.

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