Training Intensity: Load, Effort and Repetitions in Reserve

The word intensity causes confusion because people use it to describe different parts of a workout.

A set can use a heavy load without taking you very close to your limit. A lighter set can feel extremely demanding if you continue until you can barely complete another repetition.

To make a training instruction useful, specify which meaning you intend.

Intensity of load

Relative load is often expressed as a percentage of your one-repetition maximum, or 1RM: the heaviest weight you can lift once in a particular exercise under the specified conditions.

If your bench-press 1RM is 100 kg, an 80 kg load is 80% of that maximum. The calculation is:

Relative load = training weight ÷ one-repetition maximum × 100.

The number describes the load, not how exhausting every possible set with that load will be. One repetition and a near-limit set of repeated efforts are different exposures even when the bar weighs the same.

Your maximum also depends on the exercise, technique and testing conditions. A result from one machine should not be treated as the maximum for a different one.

Intensity of effort

Effort describes how demanding the set is for you. One useful approach is repetitions in reserve, or RIR: an estimate of how many additional repetitions you could have completed with the intended technique.

Two repetitions in reserve means you estimate that about two more were possible. It does not mean you must attempt both to prove the estimate.

A resistance-training-specific RPE scale links ratings of perceived exertion to this idea: RPE 10 corresponds to no repetitions remaining, RPE 9 to about one and RPE 8 to about two.¹ This specific scale should not be confused with every other RPE scale used in sport.

The same load can produce different effort

Imagine using the same weight for several sets. The first set may leave several repetitions in reserve, while a later set becomes much more demanding because you have accumulated fatigue.

Relative load has not changed, but your capacity at that moment has. Recording effort alongside weight and repetitions helps describe the session more clearly.

A difficult day also does not necessarily mean that your underlying strength has suddenly disappeared. Sleep, recent training and the session’s demands can affect performance.

Are percentage-to-repetition tables exact?

No. They can provide rough orientation, but a particular percentage of 1RM does not guarantee an identical repetition limit across people, exercises and conditions.

Avoid building a program around the assumption that everybody can perform exactly the same number of repetitions at 60%, 80% or another percentage.

Likewise, there is no need to claim that crossing one exact percentage instantly activates every muscle fiber or makes every repetition maximally stimulating. A useful training plan considers the load, effort, total work and exercise rather than reducing adaptation to one threshold.

RIR is an estimate, not a measurement device

People can misjudge how many repetitions remain. Research on in-set RIR estimates found that accuracy depended partly on proximity to failure and the number of repetitions performed.²

That makes the estimate useful but imperfect. Practice, consistent technique and looking at trends are more helpful than pretending that a reported two RIR is always exactly two.

For learning purposes, make conservative choices where failing a repetition would be difficult to manage, such as an unsupported heavy barbell press.

What to record

A practical log can include the exercise and variation, weight, repetitions for each set, and a rough effort estimate. Add a note when the range, equipment or setup changes substantially.

These details help you tell whether you progressed in the intended task. See linear progression for organizing load increases and training to failure for deciding when to end a set.

Sources

1. Zourdos MC et al. Novel Resistance Training-Specific Rating of Perceived Exertion Scale Measuring Repetitions in Reserve. J Strength Cond Res. 2016;30(1):267–275. https://pubmed.ncbi.nlm.nih.gov/26049792/ DOI: 10.1519/JSC.0000000000001049. ↩

2. Zourdos MC et al. Proximity to Failure and Total Repetitions Performed in a Set Influences Accuracy of Intraset Repetitions in Reserve-Based Rating of Perceived Exertion. J Strength Cond Res. 2021;35(Suppl 1):S158–S165. https://pubmed.ncbi.nlm.nih.gov/30747900/ DOI: 10.1519/JSC.0000000000002995. ↩