Why Reps in Reserve Is Not the Same as Training Intensity
A conceptual paper challenges the widespread misuse of 'reps in reserve' as a proxy for training intensity — with real implications for program design.
Summary
A new paper in Medicine & Science in Sports & Exercise argues that 'repetitions in reserve' (RIR) — the number of reps you could still perform before failure — is fundamentally not the same as training intensity. Intensity in resistance training is classically defined as the load relative to your one-rep maximum (percentage of 1RM). RIR, by contrast, describes proximity to muscular failure, which can vary widely at any given intensity depending on the number of reps performed, the exercise, and the individual. Conflating these two distinct variables leads to flawed program design and muddled research comparisons. The authors, affiliated with Spanish sports science institutions, call for a return to foundational exercise science definitions to improve clarity in both research and practice.
Detailed Summary
Precise terminology is the foundation of good science — and in resistance training research, imprecise language may be quietly distorting both study designs and real-world programming decisions. A new conceptual paper published in Medicine & Science in Sports & Exercise takes direct aim at one of the most common terminological errors in modern strength training: treating 'repetitions in reserve' (RIR) as a measure of training intensity.
The authors argue that intensity, as classically defined in exercise science, refers to the external load placed on the body relative to an individual's maximum capacity — typically expressed as a percentage of one-repetition maximum (%1RM). RIR, on the other hand, is a measure of proximity to muscular failure: how many additional repetitions a person could complete before being unable to continue.
These are related but distinct constructs. A lifter performing 10 reps at 60% of their 1RM may have 5 reps in reserve. The same lifter performing 3 reps at 90% 1RM may also have approximately 5 reps in reserve. The load intensity differs dramatically; the RIR does not. Using RIR as a substitute for intensity thus obscures a critical variable and makes cross-study comparisons unreliable.
For clinicians and coaches, the practical stakes are significant. Programming decisions around muscle hypertrophy, strength development, and injury risk all depend on accurately distinguishing load from effort. Conflating them can lead to under- or over-loading athletes and patients alike.
The authors, representing a Spanish strength training research network, are calling for a return to foundational definitions to restore rigor. While the paper is conceptual in nature and does not report new experimental data, its argument has broad relevance for anyone designing or interpreting resistance training research or programming.
Key Findings
- RIR (reps in reserve) measures proximity to failure, not the load used — these are distinct variables.
- The same RIR can occur at vastly different %1RM loads depending on rep range and exercise.
- Conflating RIR with intensity distorts research comparisons and real-world program design.
- Classic intensity definition (%1RM) should not be replaced or conflated with effort-based metrics.
- Returning to foundational terminology is essential for scientific rigor in strength training research.
Methodology
This is a conceptual or position paper rather than an experimental study. No participants, interventions, or statistical analyses are reported. The argument is built on established exercise science definitions and logical analysis of how RIR and intensity are used in the literature.
Study Limitations
The summary is based on the abstract only, as the full text is not open access. As a conceptual paper, the arguments are not validated by new experimental data and represent the authors' theoretical position. The paper may not account for practical scenarios where RIR is a useful adjunct metric when 1RM testing is impractical.
Enjoyed this summary?
Get the latest longevity research delivered to your inbox every week.