Intensity

In plain words

The word carries two meanings in the gym. In research and strength programs it means load: the percentage of your one-rep max on the bar. In everyday talk, and in some bodybuilding writing, an intense set means one pushed hard, which is what RPE and reps in reserve measure. The two come apart. A single at 100% is heavy by either reading. Twenty reps to failure at 50% is light by load and very hard by effort. Helms and colleagues describe RPE as a way of estimating the intensity of a set, which shows how easily the two mix. This glossary uses intensity for load and says effort for how hard a set was.

An example

Say your bench press one-rep max is 100 kg. A set of ten at 60 kg is 60% intensity, five at 80 kg is 80%, and the single at 100 kg is 100%. The ACSM's 2026 position stand found maximum strength was enhanced by loads of 80% or more. The ten at 60 kg can still leave you breathing hard: that is effort, not intensity.