The last reps matter most: Understanding Proximity to Failure

Training to the correct intensity is probably the most important aspect of resistance training. It matters more than the specific exercise you train, and how many reps you do. Reaching the right intensity is critical to increasing strength, growing muscle, and progressing your training.

There are a number of ways to measure and prescribe intensity in training. We can use percentages of a previously measured Repetition Max effort, such as a 1RM. We can also use the velocity loss during a set, as measured by Velocity-Based Training technology, such as an app or a linear position transducer. Finally, we can use a subjective method such as Rating of Perceived Effort (RPE) or Reps in Reserve (RIR). RPE and RIR work very similarly, where they both subjectively measure the proximity to muscular failure at the completion of the set. RPE works on a 10 point scale, where RPE 10 is perceived to be having 0 reps left in the tank, RPE 9 would be 1 rep left, etc. RIR is flipped to RPE, where an RIR 2 is having 2 reps left, RIR 3 is 3 reps left, etc.

There are pros and cons to all of these methods, but we’re going to focus on RPE. This is because it is a measurement of the body’s response to training, known as the Internal Load. The Internal Load is what drives adaptation, the External Load is simply how we apply training (weight, sets, reps, etc.). Percentage-Based Training and Velocity-Based Training are prescriptions of an External Load, which doesn’t account for all the other factors that affect the body’s response to training, such as stress, fatigue, and nutrition. You can read more about Internal and External Load in my previous blog post

The stress on the neuromuscular system that occurs as you get closer to failure is what promotes the body to increase muscle and become stronger. The closer you are to muscular failure, the greater the stress on your body. The research consistently suggests you need to be training within 5 reps of failure, or an RPE 5 to experience a sufficient stimulus to increase strength and increase muscle size. In practice, I generally prescribe RPE 6 and above, as it gives a buffer of one rep to get an effective stimulus. It is also significantly easier to assess your RPE the closer you are to failure.

Beginner trainers will generally make progress just by stepping into the gym. They might not need to train so close to failure, but at some point it will become necessary to work to an RPE 6 or above to continue progressing.

Judging your RPE can take practice, but it’s probably the most valuable tool you can give yourself, to ensure you’re training effectively. There are a number of ways you can identify if you’re training close enough to failure.

1. Your rep speed slows down, even though you’re trying to move the weight quickly.

2. It feels more challenging to maintain your technique, and you might even feel it changing during the hardest reps.

3. Use AMRAPS occasionally to gauge your intensity. Going to complete failure gives you a great indication as to how close to failure you’re training. If you’re going to use AMRAPs, use them for exercises that are easy to fail, such as machine-based exercises and dumbbell variations, where you won’t need to re-rack a barbell.

Your ability to judge your RPE does not need to be perfect. If you can get within +/- 1 RPE, this still gives you a powerful tool to ensure that whether you’re feeling on top of the world, or like a sloth waking up from a nap, your training can still be effective.

When people talk about ‘Big Rocks’ of training, understanding Proximity to Failure is one of the biggest. It is the key to effective training, getting stronger, increasing muscle, and making progress.

Click on the image below to watch my video about how to tell if you're training hard enough.