Training To Build Muscle: How Hard Should You Push?

When I first got into lifting, I couldn't help but notice how pro bodybuilders would push themselves to the absolute limit during every workout. 

I quickly bought into the idea that the key to progress was pushing my body until I could barely move. After all, that’s what everyone seemed to say, right? “The muscle only grows when it’s pushed to failure.” The belief was that unless you’re absolutely drained at the end of a set, you’re not working hard enough.

But is that really the truth? Is pushing yourself to exhaustion the best way to train? It turns out, the science behind it is a bit more complex than we often hear.

There’s a concept in fitness called "reps in reserve" (RIR), which measures how close you are to failure during a set. Here’s how it breaks down:
    •    Zero RIR means you couldn’t do another rep even if you tried.
    •    One RIR means you could squeeze out one more rep, but that’s it.
    •    Two RIR means you had two reps left in you when you stopped.

Most research shows that you’ll see the best progress when you finish a set with somewhere between zero and three reps in reserve. If you’re stopping with more than three reps left in the tank, you might not be pushing yourself hard enough.

But here’s where it gets interesting: training all the way to failure isn’t necessarily better than stopping just shy of it. In fact, a recent study showed that experienced lifters—those with over three years of training—had very similar muscle growth whether they went all the way to failure or stopped with one or two reps left.

So, what does that mean for your training?

    •    If you're a beginner (less than a year of lifting): Focus on leaving one to three reps in the tank for most of your sets. At this stage, technique is key—especially on compound lifts like squats, deadlifts, and presses. If you're curious about what training to failure feels like, try doing it with machines or cables toward the end of your workout.

    •    If you’ve been lifting for a while (more than a year): Try stopping with one or two reps in reserve for most of your sets. For exercises that are lower-risk (like arm work or machines), feel free to push the last set to failure.

If you’ve never trained to failure, it’s hard to really know what that "one to three reps left" feeling is like. That’s why, unless I’m doing heavy lifts like squats or deadlifts, I often push my final set to failure. It’s just how I gauge that I’m working hard enough.

Bottom line:
If you’re leaving the gym feeling like you’ve put in the work and are consistently making progress toward your goals, you’re doing just fine. But if you’re feeling stuck or unsure whether you’re pushing hard enough, it might be time to step it up and train a little harder.