YOU SAID:

my arm is getting really tired

INTO JAPANESE

私の腕は本当に疲れて

BACK INTO ENGLISH

My arm is really tired

INTO JAPANESE

私の腕は本当に疲れました

BACK INTO ENGLISH

My arms are really tired

INTO JAPANESE

私の腕は本当に疲れています。

BACK INTO ENGLISH

My arm is really tired.

INTO JAPANESE

私の腕は本当に疲れている。

BACK INTO ENGLISH

My arm is really tired.