How to Use Reps in Reserve (RIR) to Build More Muscle

OLD-SCHOOL BODYBUILDERS will tell you that the most surefire way to build muscle and feel the effects of your effort is the pump. The swollen sensation that comes when your target muscles are engorged with blood is the highlight of training for many meatheads, so much so that “chasing the pump” is a go-to descriptor for a particular approach to workouts, filled with marathon sets to capture the feeling.

Yes, you can build muscle when you chase the pump—but you’re leaving gains on the table when you exhaust yourself in its pursuit. There are limitations to what you can accomplish when you’re training with that objective, since you’ll likely be using isolation exercises to target specific muscles rather than compound movements and lighter weights to be able to take on a high volume of reps. You won’t be able to train as intensely as you need to for maximal muscle growth.

There are more effective ways to build muscle and more efficient methods to go about it. Specifically, an approach often called reps in reserve (RIR).

How to Use Reps in Reserve to Build Muscle

The approach is relatively simple, according to MH fitness director Ebenezer Samuel, C.S.C.S., who broke it down as a solution to the common mistake of chasing the pump in his Don’t List video for building muscle. Using RIR in your workouts will allow you to train with the intensity needed to create stimulus for muscle growth, and the concept is exactly as the name implies: RIR refers to the amount of reps you could realistically perform (with good form) if you were to keep going after the prescribed reps were completed.

Here’s how to apply it: For all of the working sets of your session, challenge yourself to the point that you feel like you would only be able to complete two more reps. You’re not training to failure here; that approach can be useful in specific scenarios, but you would burn out too quickly to achieve the type of muscle-building stimulus you’re hoping to elicit if you fail each set. If your training plan was to perform 3 sets of 8 reps, for example, you would push to make the eighth rep hard enough that you would only be able to perform two more with good form.

“The final rep that you do is going to be slower than the earlier reps that you did, and is going to be hard and challenging,” Samuel says. “You might have a little bit of doubt whether you can actually complete the rep with good form.”

That struggle is what you’re aiming to achieve. Samuel says that it’s okay if your form wavers a bit near the end—but make sure that you don’t push beyond your limits.

If you find yourself finishing that final rep easily, on the other hand, that doesn’t mean to push to 10 or 12 reps for every set. Instead, use that as a gauge of your effort. That’s a sign to use heavier weights so that you can reach the level of intensity you’re aiming to achieve.

Want to know more about building real muscle? Check out the MH Ultimate Guide to Muscle-Building, which features the advice, exercises, and training plans you need to achieve your goals.