If you are new to using RPE/RIR, do not panic. Let's start by defining RPE and RIR. RPE stands for Rate of Perceived Exertion, and RIR stands for Reps in Reserve. Both are tools to measure the intensity of any set in your training subjectively.
The only difference between RPE and RIR is that RIR is used for rep-based exercises, whereas RPE can be used for other types of training as well, such as HIIT, timed exercises, etc.
The RPE scale below was popularized in powerlifting by Mike Tuchscherer from Reactive Training Systems. It is a scale of 1 to 10, with 10 being maximal effort. For example, if you are programmed a top set of 5 @ RPE7/3RIR, that means after completing the fifth rep on the top set, you could have completed three more reps if you had to.
Using RPE/RIR in training allows the athlete to auto-regulate the load based on how they feel that day. If you feel strong on a particular day, you can increase the load to match the prescribed RPE/RIR, or if you are having an off day, you can decrease the load to match the prescribed RPE/RIR as well.
For example, if you are programmed a top set of 5 @ RPE8/2RIR with a recommended load of 225 but your last warmup moved well, you could potentially increase the load to 230-235. On the other hand, if you're having an off day and 225 might be too heavy for a top set of 5 @ RPE8/2RIR, then you might want to reduce the load to 215-220.
After lifting for many years, it becomes difficult to progress every week linearly, so using a tool like RPE/RIR is beneficial to ensure continued progress. As coaches, we sometimes use percentages to write an athlete's training program for those who have been consistently training and have tested their 1 rep max. However, a new lifters program will be structured differently. The RPE/RIR tool will allow the coaches to determine the new lifter's percentage for their 1 rep max on the squat, bench, and deadlift once they have been training consistently.
Lastly, RPE/RIR is beneficial for accessory movements (belt squat, lat pulldown, dumbbell bench press, etc.). Almost no one knows their 1 rep max on something like a belt squat, so we would never program a percentage for that kind of movement. Instead, we would program something like 3x12-15@RPE8/2RIR. If you have never done a particular exercise, pick a weight that you think will be appropriate for the prescribed reps at the prescribed RPE/RIR. Always start conservative and add as you go.
RPE/RIR is a skill, just like lifting weights. In the beginning, you will undershoot and overshoot your RPE/RIR. Be honest with your assessment, ask yourself immediately after completing a set, and rate all your sets. The more you do it, the better you will become at using RPE/RIR.
If you have any questions, shoot us a DM on the SoCal Powerlifting IG. We are happy to help!