The starting point of this concept lies in the objective fact that all training volume can't be created equal. Thus all reps aren't equal too.
That's why scientist James Krieger brought up an entirely new concept called exertion load and how it could be a better way of predicting muscle growth.
Dr. Layne Norton, renowned physique prep coach and powerlifter recently posted a video on social media about a metric that takes exertion during training into account.
Created as a computer software application by strength and conditioning coach Robert Frederick this metric was discussed during a seminar by aforementioned researcher James Krieger.
Prefers Reps in Reserve (RIR) and Rating of Perceived Exertion (RPE)
Norton, who attended the Krieger seminar on muscle hypertrophy, prefers reps in reserve (RIR) over the more commonly used rating of perceived exertion (RPE) because it takes intensity into account.
Basically, it is the same as the RPE system, just in reverse. The number 0 stands for max effort, and the number 1 means you could have completed another rep. RIR basically outlines how many reps you should have in reserve when finishing a set. The idea is to complete a set with a predetermined number of RIR, which is how many you could do if you took that set to failure.
The research on muscle hypertrophy has shown that the total volume of training is more important for stimulating muscle growth than a specific rep range.
In other words, while you can still lift light weights and produce hypertrophy, you will fail if the intensity is too low.
“Training volume is defined as the number of sets, multiplied by the number of reps, multiplied by the weight used,” explains Norton.
“There is a problem using training volume as a marker for hypertrophy, though, because it can be misleading as exertion is not taken into account. For example, I can take a 45 pound (20kg) barbell, put it on my back and do 10 sets of 100 reps and never get close to failure, despite reaching a very high training volume. Will that initiate hypertrophy?"
"Exertion load takes into account your exertion during a training session. It uses volume, but also incorporates what is called your RIR (reps in reserve). If I did a set of 10 with zero RIR, that means I went to failure and could not do another rep with good form. If I went to an RIR of 1 that means on my 10 rep max, I would have done 9 reps. So, I left a rep in the tank. If I would have done my 10 rep max for 8 that is an RIR of 2, 7 is the RIR of 3 and so on.”
What are the other scientists' views?
Powerlifting coach Mike Tuchscherer believes in setting targets. “Don’t go to the gym with no idea of what you are doing. A target weight to aim at will improve your training. Auto-regulation allows you to finetune that weight up or down based on how you are performing at the time. This will also allow you to do visualisation and give you the additional motivational factors that targeting weights can provide.”
Researchers Eric Helms and Michael Zourdos developed this idea. In their turn, specialists recommend using reps in the range of 6–12, with an RIR-based RPE of 8–10 (RIR 0–2).
“Training at an RIR of 0 (to failure) should be implemented in a manner so as not to potentially reduce volume on subsequent sets due to fatigue, and therefore limited to the final set performed for a given body part, and should primarily be relegated to exercises with a low biomechanical complexity and risk of injury, such as isolation movements.”
“All volume is not created equal,” adds Norton. “The concept of exertion load may be a better predictor of strength and hypertrophy than just overall volume. At this point we know 8 to 15 reps done with a high level of exertion seems to be the best way to elicit hypertrophy. It is, however, still useful to do lower reps as part of a daily undulating periodised programme, because when you do strength training you will get stronger and you will be able to create more overload in the hypertrophy rep range.”
According to Norton, exercise scientists are only “scratching the surface” of what is defined as optimal training.
“What works best in studies may not be what works best for you. People have very divergent responses to different modules, such as strength training versus power training, the rate of force development and how it applies to you as an individual.”
Helms echoes Norton’s sentiments about training individuality: “People adapt at different rates, to different magnitudes, and the best training approach for one person might be pretty crappy for someone else. Auto-regulation, simply put, is just a structured approach for embedding a respect for individual variation within a programme.”
Helms states there are advantages to using both light and heavyweight loads in the gym over time. “Light loads when progressed over time accumulate more total volume, while heavy loading results in greater increases in strength, which can increase mechanical tension. If anything, it is likely that the synergy of the two will result in the greatest longterm hypertrophy. I stress long-term because 99% of research is a collection of 4-to-12-week studies, which can’t tell us everything.”
He sees hypertrophy as a component of strength, not the other way around. “If you are effectively overloading muscle and generating hypertrophy, you will get stronger over time. A large part of that strength increase is also due to motor learning, skill development with the exercise, neurological adaptations, and other structural changes. Strength increases are a good marker for the effectiveness of your training programme.”
To be effective in the gym, Helms suggests a plan to increase training loads over time. “Strength occurring as a natural outcome of the training itself does happen, but primarily in novices and intermediates. Past that stage, it requires training with a little more purpose!”
Recommendations from the founder
As Muscle Evolution reports, the RIR app developer, Frederick, views the most productive gym session as the one where you perform your heaviest sets of the day between 1 and 4 RIR.
“The first heavy set of the day should not be higher than RIR = 4. If it is, add a little extra weight on your next set so that RIR comes down a little bit, but not so much that it drops to 0 at any point in your workout."
"A set with 0 reps in reserve is a set done to failure since no more reps were possible. Use RIR to adjust your weights to how you feel. If you feel particularly strong, you can use RIR as a guide for adding extra weight. But you may not feel the same in the next workout, so the app won’t automatically increase your weight above normal."
"One easy way to get a little extra work done when you feel strong is to do the reps with longer pauses and explosive concentric tempos. A little extra power at the bottom is usually not a bad idea, and it simplifies all the confusion about weights, reps, and sets. Don’t make every workout hard. You need easy, medium, and hard workouts.”