Effective reps is something that, as we American say, Borge Fagerly or Borge Fagerly talked about a long time ago, when he discussed and creating Myo-reps. It’s something that Chris Beardsley of the Strength and Conditioning Research Review has talked a fair bit about as well as other people in the sphere of lifting.
The basic idea is that certain reps are more stimulating. Specifically for hypertrophy which has, of course, knock on effects of strengths if you generate more size. You do recruit high threshold motor units. You’re going to probably induce more strength gains, but this is a primarily a discussion for hypertrophy.
Basically, it’s only the last few reps in the set where you perceive the barbell or the dumbbell to be slowing down due to accumulative fatigue that are creating a robust stimulus.
For example, let’s say, we’re going back to that 12 to 15 reps with 70 percent of 1RM, the argument would be then only in the last five reps or so, where you actually start to see the barbell slow down rep to rep to rep as you approach failure, are producing a close to maximum stimulus, while most of the earlier reps are simply there to generate the fatigue to allow you to perform those “effective reps.”
This is come about and has some utility but also has some holes in the theory. We used to say like maybe five years or so ago that that volume load was a predictive factor of hypertrophy, that being sets times reps times load.
But as we started to look more other factors, we saw that volume load only in certain conditions seem to be predictive hypertrophy, and indeed, a set of 6, and a set of 15 to failure, while the set of 6 being closer a 1RM will be better for strength development, they’re actually quite similar in terms of the stimulus for hypertrophy, even though one has about twice the volume load of the other.
You know, if you were to do a set with your 15RM, which is going to be lighter than a set with the load you use for your 6RM, one is going to be about the twice volume load is the other.
However, a 15RM does not produce twice as much hypertrophy. In fact, they produce almost identical levels of hypertrophy. That’s because in the end, when you do a set to failure, that has enough reps in it to produce sufficient time under tension, you’re getting to the same point.
The way to think of this is that if you’re going to do 15 reps, you’re going to have different motor units getting cycled in to pick up the slack as other motor units and the fibers they innervate are fatiguing. So as different muscle fibers are working towards pushing these reps of these 15 reps set up and up and up and up and up, eventually, they’re going to fatigue and someone else has to come in and pick up the slack.
These high threshold motor units will get cycled in to continue that force production. Eventually, they too will fatigue until everything is fatigue and you’ve effectively trained everything to its maximum capacity having done 15 reps out of a total possible 15.
Now, the same thing basically happens on a 6RM. We know from Henneman’s size principle that if you lift a heavy enough load everything is recruited. Essentially, our muscles recruit only the fibers they need to lift the load and due to the fatigue or lifting a really heavy load, that can mean more and more fibers are recruited.
When you lift a very, very heavy load all the way from you slow-twitch fibers all the way to your fast-twitch fibers are recruited almost immediately. If you lift a six rep max, pretty much everything is recruited automatically. Then after the six reps are done, everything has been effectively trained and the large motor tension has been put on the muscles.
You’ll notice that the first rep on a 6RM is pretty slow and that only gets slower from there. Whether you’ve done a 15RM or a 6RM, you’re getting to the same place is essentially the point. While the entirety of that 6RM might be “effective reps” the argument would be that only once you start to see the barbell velocity slow in a 15RM are you achieving effective reps.
What we know to be true from the research is that when you’re comparing any load from say about 40 percent of 1RM up to say your 5RM or 6RM a set to failure is about equivalent to any other load for the stimulus for hypertrophy.
It means if you take a set of 30 to failure or say your 40 percent 1RM to true failure, which is hard to do because the metabolic fatigue will confuse you as to when you’re actually there. Where you take a 6RM to failure, they’ll have the same stimulus.
But where it starts to fall apart is when we look at studies that are not to failure, sometimes we see similar hypertrophy especially in trained lifters that kind of throw some wrenches in the idea of effective reps.
The problem with the effective reps theory is that while it makes sense on paper and has solid theoretical support there are enough studies now where the non-failure group might actually get more hypertrophy or there’s no difference in hypertrophy between the two groups.
That is probably a little more complicated than that. There are probably interactions between what is the prime mover, what’s the secondary muscle group. Not all the muscles are necessarily contributing the same amount, fatiguing at the same rate. Advance lifters also seem to be able to recruit high threshold motor units earlier in a set.
If you’re lifting to maximum concentric velocity, that might also change things, that’s another way to recruit muscle fibers. Then you might induce fatigue a little earlier and get more growth out of that.
There probably is some effect of the total amount of work done, it’s the effect of metabolic stress can’t be discounted. That might put, higher rep sets on more equal footing than you expect. You have to consider that if you’re going really, really heavy and you can only get three reps. Those are just three effective reps.
We have data to show that sets of 2 to 4RM — if you equate the number of sets — doesn’t produce as much growth as sets let’s say 8 to 12RM .That’s simply because you’re not spending enough time actually lifting. It’s too heavy for you to complete a sufficient amount of time under tension to fatigue all those fibers.
There is a useful way of looking at training when you talk about effective reps, but I don’t think it’s to the point where it’s a model that predicts hypertrophy.
We’ve seen studies go against that model enough times now, that I’m not confident. I think it is useful to think about maybe why hypertrophy can be equal between a low load and a high load set at failure.
If you understand that, you basically get to the same place but through different means to recruit and train all those fibers. That’s where the utility ends in my opinion. I’ve seen some very hard line positions with effective reps were basically, “Hey, only the last five reps in a set to failure counts.
Either therefore you should be training with moderately heavy loads all the time. High reps are simply just unnecessarily fatiguing and burning a lot of calories.
I have seen the position that basically you should always train to failure to ensure that you’re getting the most effective reps each time. Forgetting the big picture of how much that might induce disproportionate fatigue or risk injury or create burnout.
Useful paradigm probably doesn’t accurately model hypertrophy in response to how close to failure you go or the number of reps in a set, or what RPE you train at. In fact, in my PhD, the final study we did, we took trained lifters doing the squat and the bench press. These are reasonably strong people.
By the end of the study, they were on average squatting close to 400 pounds these males and benching well into the 200s. One group trained with a percentage 1RM, the other group trained with RPE. The percentage 1RM group gained strength at a faster rate than the percentage 1RM progression.
They ended up training at roughly a five to six RPE throughout the whole study. That means that they had four to five reps left in the tank throughout the whole study. Which means that they almost did no effective reps, if you use that kind of hardline position.
While the other group started at a 5 RPE, and trained all the way up to a 10 RPE by the end of the study. They had on average about an 8 RPE, meaning that they were getting, at least three of those five effective reps on average throughout the study.
You would expect to see no growth in one group and some growth in the other. In fact, when you compare the muscle thickness changes in the pectoralis major, in the quadriceps there was no significant difference between the two groups. The actual percentage changes and mean values were quite similar.
It doesn’t always add up. That’s where we need to probably look a little deeper into this model. Not just base it off of the observation that sets to failure at various different intensities produce hypertrophy.