Tell us if this sounds familiar: You start working out and you immediately see results. You run faster; you can lift more. But a few weeks later, you stop seeing progress. Plenty of trainers and workout programs (ahem, P90X) swear by muscle confusion theory. They say you can avoid fitness plateaus if you change up your workout frequently enough, effectively tricking your body before it gets too used to one routine.

But this is just another exercise myth, says Martin Berkhan, founder of LeanGains. You’ll see plenty of gains if you do the same kind of workout, whether it’s arm day or running, so long as you add intensity (reps, weight, or distance) over time. Plus, muscle confusion makes it super hard to actually measure progress. “Do the exercises in the same order and in the same routine that you did last week,” Berkhan says. “Did you do one more rep with the same weight, or the same number of reps with five pounds more? That’s progress.”

To be clear, we’re not saying you’re now glued to one routine. Exercise is supposed to be fun, not boring. Just know that fitness plateaus happen—and trying to “confuse” your muscles won’t help.

(h/t Science of Us)