rep out

rep out

To be unable to do any more repetitions of a strength-training exercise due to physical exhaustion. Man, my arms are out of shape. I repped out after just five bicep curls! You shouldn't just keep pushing yourself until you rep out, or you could end up really injuring yourself.
See also: out, rep
Farlex Dictionary of Idioms.

rep out

in. to do too many repetitions of an exercise and reach exhaustion. After forty crunches, he repped out. He’s got some work to do.
See also: out, rep
McGraw-Hill's Dictionary of American Slang and Colloquial Expressions
See also:
  • be on (one's) last legs
  • flack out
  • fling (one's) arms up in (some emotion)
  • fling up (one's) arms in (some emotion)
  • take a lot out of
  • take a lot out of (one)
  • wacked
  • wacked out
  • whacked out
  • out of shape