Do You Need to Hit Failure to Maximise Muscle Growth?
Take-aways
Training to 1-2RIR may cause similar muscle growth as training to failure.
At the very least, the difference is probably small enough that training at 1-2RIR, on average, is a great approach. Some sets can/should still be taken to failure.
Training to failure seems to persistently cause greater fatigue than training a few reps shy of failure.
Since subsequent performance takes a hit, it’s probably worth taking only the last few sets of an exercise to failure, and keeping failure for later in any session.
If you’ve been paying attention, you’ll have seen the meta-analysis on proximity-to-failure by Robinson and colleagues. It made waves within the fitness industry, finding that the closer a set was taken to failure, the more muscle growth occurred.
So, do you need to take a set to failure to maximise muscle growth? Maybe. Or, maybe not, according to a new study by Refalo and colleagues. Using a within-participant design, they compared performing leg press and leg extensions to 1-2RIR vs going all the way to momentary failure.
As a side note, within-participant designs allow us to have greater confidence in the findings, all else being equal. This is because potential confounders like sleep, stress, nutrition, etc. are equated for between the two groups - after all, one’s right/left legs are both still attached to the same body.
As you can see, muscle growth was very similar between the two conditions.
Interestingly, performance loss (how many reps could be performed with a given load) from the first to the final set was consistently greater when training to failure vs 1-2RIR, from week one to week eight in the study. This suggests a couple of things.
First, training to failure probably does remain more fatiguing, even as you grow accustomed to it. Second, it’s probably worth reserving failure for later sets within an exercise/session; while going to failure too early in the session is unlikely to dramatically harm stimulus, it’s probably still worth avoiding the detriment to your performance.
Why?
Taking a set all the way to failure may not be necessary to maximise hypertrophy: that is one possible interpretation of the findings. Alternatively, the difference in hypertrophy stimulus between 1-2RIR and failure may just be so small that it requires a relatively bigger sample size to consistently detect. Personally, I’m inclined to opt for the latter interpretation: at the very least, though, this study does suggest that any differences in hypertrophy between 1-2RIR and failure will be modest to small.
