'If your last rep looks like your first, you wasted your time' Is It True?
Introduction
Today we are going to be examining one of the more current “hot takes” on Fitness Twitter/X, “If your last rep looks like your first, you wasted your time.”
Before I challenge the claim, let me say that I very much appreciate this sentiment. More often than not, newbies and intermediate lifters may not have a good sense of what training to failure looks or feels like.
Giving newbies the mental imagery of one fresh rep at the start of a set, and another rep that is slowed or a struggle at the end, is a very clever use of imagery.
Having said all of that, on a purely scientific level, we need to put the claim to the test. But before we jump in, let’s define some terms.
Relative Effort & Growth Stimulus
We measure a set’s proximity to mechanical muscle failure using RIR, or repetitions in reserve. This is the approximate number of reps you have remaining before you come to complete muscle failure on an exercise.
1 RIR = one rep in reserve, 2 RIR = two reps in reserve, etc.
The importance of relative effort to muscle failure is in its ability to help us estimate how close we are to approaching the kind of reps that activate the growth-prone motor units to being activated and driving tension. The reps that effectively grow the muscle are the reps closest to muscle failure.
Some facts about reps and their stimulus:
All reps are stimulative, for the record. Just not stimulative enough for muscle growth.
As you approach 0 RIR, the growth stimulus goes up.
The last 5 reps in a set taken to failure, activates growth-prone motor units.
'If your last rep looks like your first, you wasted your time' Is It True?
Video: Pendulum Squat taken ~0 RIR
Second working set
0 RIR
Reps = 6
According to the claim, did I waste my time?
If we compare between the first and last rep, there does seem to be a noticeable difference in the cadence of the concentric of the final rep.
So according to the claim, I didn’t waste my time! Fantastic news.
But what about the reps before the final rep? Were those a waste of time?
According to the scientific literature discussed above, the final 5 reps were all stimulative for muscle growth — a number of which didn’t look TOO dissimilar to the first rep.
In fact, the second rep looked a lot like the first, and that was ~5RIR (I know, I know, it’s 5 RIR — I get it). But the the third was 4 RIR and didn’t look too dissimilar to the first…
In fact, 1 RIR didn’t look all that much different than the first rep. If you looked closely in the videos below, could you tell? — sure? Maybe? but it’s pretty close for 1 RIR.
The last five reps, according to the scientific literature, are all stimulative for muscle growth.
Concluding Thoughts: My Verdict
Will training within 5 RIR be your best strategy to train for hypertrophy? No. Anywhere in the 3-0 RIR range is recommended. Personally I prefer the 1-0 RIR rep range for my own programming. So with my own preference for effective training in mind, I will conclude by saying that I agree with the claim 'If your last rep looks like your first, you wasted your time'— SPIRITUALLY. Scientifically however, theres some room for nuance.