If you get equally tired from different workout routines, how much muscle you build might depend more on how tired you are than on how many sets or reps you do.

What we've found so far is that the evidence does not clearly support the idea that muscle growth depends more on fatigue than on training volume when total fatigue is the same. Our analysis of the available research shows that 41.0 assertions support this idea, while 48.0 assertions refute it [1]. This means the balance of evidence we've reviewed leans slightly against the claim. We looked at a total of one key assertion that addresses this question, and it suggests that if you're equally tired after different workouts, muscle growth might depend more on that fatigue than on the number of sets or reps you do [1]. However, nearly half of the evidence we analyzed contradicts this idea. Since more assertions oppose it than support it, the current data we’ve gathered does not strongly back the claim. We want to be clear: this doesn’t mean the claim is false. It means that based on what we've reviewed so far, the evidence isn't pointing strongly in that direction. There may be factors we haven’t fully accounted for, and our understanding could change as we analyze more studies. Right now, we can’t say that fatigue matters more than volume for muscle growth—even when total fatigue is matched. The data we have is limited and somewhat divided. We’re continuing to gather and analyze evidence to improve our understanding over time. Practical takeaway: If you're trying to build muscle, don’t assume that just feeling tired after a workout means you’ve done enough. The number of hard sets you do still appears to matter, based on what we’ve seen so far.