Reps in Reserve: Are You Training Hard Enough?

One of the most important variables in strength training is intensity of effort. In recent years, a concept called “Reps in Reserve” (RIR) has grown in popularity as a way to measure how intensely we are training during a set.

Reps in Reserve refer to the number of reps you could still perform before reaching true muscle failure.

For example, imagine you are performing a chest press. You complete 10 reps and then stop the set. However, had you continued, you actually could have completed 12 total reps before you truly reached muscle failure. In this case, you trained to 2 Reps in Reserve.

The fewer Reps in Reserve, the higher the intensity of effort. Zero Reps in Reserve would mean you trained to muscle failure — the point where you cannot complete another repetition in good form.

This concept has become increasingly useful in both research and practical strength training because it helps quantify effort level. And the research surrounding Reps in Reserve reveals a few important discoveries.

Most People Don’t Train Hard Enough

Studies consistently demonstrate that the average trainee tends to stop a set with approximately 5–6 Reps in Reserve. In other words, most people are not training intensely enough to maximize the benefits of strength training.

This matters because intensity is one of the primary drivers of adaptation. If we stop too far away from failure, we may not create enough stimulus to optimize improvements in strength, muscle mass, metabolic health, and overall fitness.

We’re Poor at Estimating Proximity to Failure

Research also shows that most people are not very accurate at predicting how many reps they actually have left.

On average, trainees misjudge their Reps in Reserve by about 3 repetitions.

This means someone may stop a set at 10 reps believing they only had 2 more reps available, when in reality they could have completed 5 additional reps.

In practical terms, many workouts simply are not as challenging as people think they are.

Experience Improves Accuracy

The good news is that training experience improves our ability to estimate Reps in Reserve more accurately.

As individuals become more familiar with hard training and the sensation of approaching muscle failure, they become better at identifying true effort levels. Experienced trainees are generally more accurate at determining how close they are to failure during a set.

This is one reason supervised strength training can be so valuable. Guidance from an expert Exercise Physiologist can help ensure the workout intensity is sufficient to produce meaningful results.

Why Training to Failure Can Be Valuable

Theoretically, training to 1–2 Reps in Reserve may produce similar benefits to training to complete failure. However, because most people underestimate how many reps they truly have left, they often fail to train intensely enough when relying solely on estimation.

Training to momentary muscle failure helps solve this problem.

By reaching the point where another rep cannot be completed in proper form, we ensure that intensity is high enough to maximize the training stimulus.

Of course, this does not mean every set must be performed recklessly or without proper supervision. Instead, it reinforces an important principle: effective strength training requires effort.

Take-Home Message

Strength train to muscle failure or at least to the point of 1–2 Reps in Reserve. Most people can do more than they think they can, and many stop their sets too early to maximize the benefits of exercise.

Intensity matters. And when in doubt, you can probably do one more rep.