Training intensity describes how demanding a set is, often expressed as load relative to maximum or effort relative to failure. This page provides a definition and practical context; it is not an individualized medical or nutrition prescription. Use the related tools and guides for calculations or programming decisions rather than treating a glossary definition as a result.
When intensity is expressed as effort rather than load, the RPE and RIR calculator converts a recent set’s reps and rated effort into a practical training-load range.
Two different definitions of “intensity”
Training intensity gets used two distinct ways, and mixing them up causes real confusion in program design. In strength contexts, intensity almost always means load as a percentage of your one rep max: a set at 85% of 1RM is “high intensity” regardless of how hard it felt. In effort-based contexts, intensity means proximity to failure, tracked through RPE or RIR, where a lighter set taken to true failure can be just as “intense” by this definition as a heavy set with reps in reserve.
Programs that only specify one definition can leave the other variable unconstrained; a percentage-based program still needs an implicit rep target to control effort, and an RPE-based program still benefits from tracking the resulting load to see whether true strength is trending up.