Your Intensity Sucks

What is intensity ?

There are numerous way of describing intensity. Load used and RPE/RIR are the most common ways of quantifying training intensity. Now, each way has it's applications depending on the context but for training directed towards muscle growth, RIR seems to be the most applicable. RIR is, simply put, repetitions in reserve. This means that RIR describes how many repetitions you had in the tank until you reached muscular failure, with muscular failure being the point where no more repetitions can be performed of a given exercise. If you are performing squats and performed 7 repetitions but could perform 10 (no more than 10) then, your RIR is 3. If you are performing dumbbell presses and performed 9 repetitions out of 9 possible (meaning you could not perform anymore) then, your RIR is 0. Pretty simple right? So, where is the problem? The truth is that most people, for one, don't even use RIR during training to quantify their intensity but even the ones who do likely have a low estimation accuracy although this can depend on the trainee.

Who estimates RIR best?

There is some evidence on whether trainees can gauge their RIR accurately. In these studies, they sometimes get their participants to "shout" during a set when they're at a given RIR (e.g. 3) and then continue the set up until they reach muscular failure. After that, it is assessed whether the participants were accurate or not. The evidence suggests that trainees who are more experienced as well as ones who are training closer to failure ( lower RIR ) can estimate more accurately whereas trainees with low training experience and/or when training further away from failure can have low estimation accuracy.

How to estimate RIR accurately ?

Ok. So, likely your next question is, how can I improve on my RIR estimation accuracy? Pretty simple. As a general, and very good, rule, the trainee should train to failure on an exercise to actually experience the true meaning of muscular failure and then use that set as a benchmark for subsequent workouts. By knowing what your rep number for muscular failure is on different exercises you can 1) know how to hit different RIRs since you already know your "0" and 2) know the feeling of training to muscular failure so you can compensate for progression and switching exercises. Now, this method is absolutely fine although an emergence of a new method allows us to estimate RIR without the need of actually going to muscular failure (0 RIR) all the time. This new method is known as velocity loss. It is a concept first introduced by Dr. Mike Zourdos in 2016. This method relates the loss of repetition speed over time with the decrease in proximity to failure, as long as maximal effort is exerted each repetition. This means that, as long as you apply maximal effort on your reps, the speed of the repetition will decay over the course of a set up to the point where there is no repetition velocity, muscular failure. Trainees may use this way of estimating their RIR during a set. Whenever a relatively significant decrease in repetition speed is noted, that likely means you are close to muscular failure. The loss of velocity becomes more noticeable as you get closer to failure so it might be worth filming your set to have a sample size for times where you don't perceive the loss of velocity as vividly. There are also applications and devices where the exact numerical data and loss of velocity can be estimated although you likely don't need this. Just understanding the concept and applying it is good enough.

What RIR should you train at?

As with almost everything in fitness, this topic is extremely nuanced. Arguments for training at muscular failure may be valid as well as the arguments that contradict this opinion. What we know for sure is that you need to be at 4 RIR, at least, on every working set. As we previously mentioned, the further away you are from muscular failure, the more likely you are to estimate your RIR inaccurately. Therefore, training a little closer to failure will not only increase your growth, but will also increase your estimation accuracy. Training at 2RIR for the majority of the time seems to be the "sweet spot" for most people when factoring in training stimulus, fatigue management, and RIR estimation accuracy.