RPE, The Stimulus and Why It Matters for Building Muscle

You’ve likely seen RPE being used more and more in the programme lately, and there’s a good reason for that.

Using RPE allows me, as a coach, to deliver a movement with the stimulus I intend, instead of prescribing a fixed weight that might be too light for some and too heavy for others. It helps make sure everyone in the session gets the right level of effort for their ability, experience, and recovery on that day.

Because at the end of the day, training isn’t about chasing random numbers. It’s about applying the right amount of stimulus to create adaptation.

Let’s break down what that means.

What Is RPE?

RPE stands for Rate of Perceived Exertion, which simply measures how hard a set feels, or more accurately, how close you are to failure.

We use a scale from 1 to 10:

• RPE 6: You could do 4 more reps

• RPE 7: 3 reps left in the tank

• RPE 8: 2 reps left

• RPE 9: Maybe 1 rep left

• RPE 10: All

  out effort, no reps left

It’s not a “how tired am I?” scale, it’s a performance scale. It helps you gauge intensity in a way that automatically adjusts for how you feel that day, stronger, tired, sore, or anywhere in between.

Why We Use RPE

Every exercise in your programme is designed to hit a specific stimulus. That might be strength, hypertrophy (muscle growth), or muscular endurance, and that stimulus only works if the intensity is right.

If I prescribe “4 sets of 10 @ RPE 8,” that tells you to choose a weight that feels like you could do two more reps at the end of each set.

That’s much more effective than saying “4 sets of 10 @ 50kg,” because for one person, 50kg might be a warm up, and for another, it could be a max effort lift.

RPE keeps the training goal consistent across everyone. It ensures the intended dose of effort matches the intended stimulus.

The Stimulus/Fatigue Balance

Think of training like a credit card:

• Each hard set is a purchase; it costs fatigue.

• Recovery is how you pay it off.

• Growth happens when you spend smartly, not recklessly.

An RPE of 8 to 9 usually gives the best return, enough effort to stimulate growth and strength, but not so much that you are wrecked for days.

If you always go to RPE 10 (complete failure), you create too much fatigue and your performance starts to drop. If you stay around RPE 5 to 6, the stimulus isn’t strong enough to make your body adapt.

RPE helps us stay in that productive middle ground where progress is consistent and sustainable.

Why This Matters for Building Muscle

Muscle growth comes down to one simple principle:

Apply a strong enough stimulus, recover from it, and repeat.

RPE helps you control that first par, the stimulus. Here’s how:

1. You train hard enough to grow. RPE ensures you are pushing close to failure, not just moving weight around.

2. You manage fatigue intelligently. By staying within the right RPE range, you can train with high quality more often, which leads to more total volume over time.

3. You adapt week to week. As you get stronger, the weight that feels like RPE 8 naturally increases. That means you’re progressing without having to force heavier loads too early.

4. You learn how your body works. Over time, you’ll develop a better feel for effort, fatigue and recovery, all key skills for long term success in training.

   
   

The Role of the Stimulus

When we talk about “stimulus,” we’re not just talking about lifting heavy. We’re talking about creating meaningful tension in the target muscles.

That happens when you:

• Control the movement

• Maintain tension throughout the rep

• Focus on quality over load

• Work close enough to failure for the body to need to adapt

An RPE 8 or 9 with controlled tempo, full range, and intent is far more powerful than an RPE 10 done with sloppy form or ego lifting.

The stimulus is the message you send to your body, and RPE helps you send that message clearly, every session.

How to Use RPE in Your Training

Here’s how to get the most out of it:

1. Start with awareness. After each set, ask yourself: “How many more reps could I have done?” That’s your RPE.

2. Compare it with your app. You should be using the app to track the weights and RPEs you use. Over time, you’ll see how your strength is improving for example; the same weight might start to feel easier, or you’re lifting more at the same RPE.

3. Adjust based on your day. Didn’t sleep well? Feeling strong? RPE accounts for that. It’s flexible and ensures you still get the right stimulus no matter how you’re feeling.

4. Trust the process. The goal isn’t perfection, it’s consistency. The more you use RPE, the better your internal gauge becomes.

   
   

The Bottom Line

RPE isn’t about overcomplicating training, it’s about making it smarter.

RPE only works if you are using it correctly. I can write a suitable number for the movement, but if that’s an RPE 9 and you’ve actually got another five reps left in the tank at that weight, then we’re not applying it properly and progress won’t happen.

It’s how we make sure you’re getting the intended stimulus from each session, progressing safely, and building muscle efficiently without burning out.

So next time you see “RPE 8” in your programme, know that it’s not just a number. It’s a target zone designed to get you the most from your training.

Train hard. Train smart. And always chase the right stimulus, not just heavier weight.