In order to make predictable progress, you should stay away from failure. Failure is the point where you fail to complete a repetition with good form or you have to ask someone to help you lift the weight back up. That shouldn’t happen. At the end of each set you should be able to perform at least one more repetition with good form. This will ensure predictable progress every week.
RPE stands for Rate of Perceived Exertion and is based on repetitions in reserve – basically how many reps you think you could have done with a given weight. The ShredSmart workouts are all based on doing straight sets – all sets are done with the same weight. RPE allows you to predict whether you’ll be able to complete all the reps with the weight you’re using before actually performing all sets. It also prevents you from pushing too hard and mess up the progression model.
I feel it would have been way easier to understand RPE if the scale was reversed and 9 RPE become 1 or 8 RPE became 2 to signify the reps remaining. But most people in the fitness community use 10 RPE to signify technical failure so I use this scale too in order to avoid confusion.
In order to be able to complete 3 sets of equal reps with the same weight, the first set needs to be around 7 RPE, meaning you could have done around 3 more reps when you stopped that set. Then your second set is going to be around 8 RPE because you’re more fatigued and finally your last set is going to be around 9 RPE.
If your first set has a 9 RPE it’s clear you won’t be able to lift the same weight for the same number of reps for two more sets. That tells you need to lower the weight in order to complete the required reps.
For optimal progress you should follow these RPE guidelines:
Set 1 – 7 to 7.5 RPE
Set 2 – 8 to 8.5 RPE
Set 3 – 8.5 to 9.5 RPE
On big leg exercises (such as squats, deadlifts, leg press, hip thrusts) the RPE is reduced to 5-6 RPE in set one, 6-7 RPE in set 2, and 7-8 RPE in set three. Training close to failure on these exercises is dangerous because there’s a high risk of injury.
Sticking to these RPE guidelines is more important for strength progression than pushing to complete the required reps. For example if your third set asks for 6 reps and a 9 RPE, the RPE takes priority. If on the fifth rep you already hit 9.5 RPE (meaning you know you probably couldn’t do one more rep) it’s best to end the set there instead of trying to push for 6 reps and inevitably fail.