Older Adults Underestimate Workout Intensity

Study finds older adults misjudge their proximity to failure by an average of 2 reps on near-maximal sets.

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If you’re training older adults in the gym and relying on their self-assessment to guide intensity, this study has important findings you should be aware of.

Researchers from the University of Castilla-La Mancha examined whether older adults can accurately predict how many repetitions they have left before failure, a method called “repetitions in reserve” (RIR) and whether ratings of perceived exertion (RPE) track with actual effort. The study involved 25 community-dwelling older adults (average age 68 ± 4 years, BMI 28.1 ± 4.6 kg⋅m⁻²) who performed chest press exercises at 65% of their one-repetition maximum (1RM).

Aim

The primary aim was to determine whether predicted RIR accurately prescribes resistance exercise dose in older adults compared to actual RIR. The secondary aim evaluated whether RPE values from the OMNI Resistance Exercise Scale (OMNI-RES) correlated with objective effort indicators—specifically, velocity loss and number of repetitions performed.

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Methods

Participants completed two testing sessions. During the first session, they performed a 1RM test on the chest press, followed by a repetitions-to-failure test at 65% 1RM to establish actual RIR values. In the second session, participants completed three sets at 65% 1RM, stopping when they believed they had 2, 4, or 6 repetitions left in the tank (predicted RIR-2, RIR-4, and RIR-6) in randomised order. Movement velocity was tracked, and participants rated their effort after each set. All participants had been familiarised with both RIR and RPE methods through a 12-week resistance training program (36 sessions total) conducted before testing.

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Results

Accuracy of RIR Predictions

Older adults significantly underestimated their capacity at lower RIR targets. When asked to stop at predicted RIR-2, participants underestimated by an average of 2.1 ± 0.3 repetitions (p < 0.001). At predicted RIR-4, they underestimated by 1.6 ± 0.6 repetitions (p = 0.003). However, at predicted RIR-6, their estimates were accurate with only a 0.1 ± 0.8 repetition difference (p = 0.823).

Velocity Loss Findings

Velocity loss—a marker of neuromuscular fatigue—was 16% lower during predicted RIR-2 compared to actual RIR-2 (p < 0.001) and 10% lower during predicted RIR-4 compared to actual RIR-4 (p = 0.009). No difference was observed for RIR-6 (0% difference, p = 0.989). This indicates participants stopped their sets prematurely when aiming for lower RIR values.

RPE Sensitivity

RPE values showed no significant differences across the three RIR conditions: 8.0 ± 0.2 for RIR-2, 7.6 ± 0.2 for RIR-4, and 7.3 ± 0.3 for RIR-6 (p > 0.05). Additionally, RPE did not correlate with velocity loss or number of repetitions at any RIR level (all p > 0.05). This suggests limited sensitivity of the OMNI-RES scale for distinguishing between different effort levels in this population.

Agreement Analysis

Poor agreement was found between predicted and actual RIR for velocity loss across all conditions (ICC values ranging from −0.147 to −0.006). For number of repetitions, moderate agreement was observed: ICC = 0.514 for RIR-2, 0.588 for RIR-4, and 0.606 for RIR-6.

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Practical Takeaways

While the RIR method lacks precision for exact exercise prescription in older adults, it still has practical value for regulating training volume. Coaches and trainers should understand that older clients will likely stop earlier than intended when targeting near-failure sets, potentially reducing training stimulus. The predicted RIR-2 condition did produce significantly greater velocity loss and higher repetition counts compared to RIR-4 and RIR-6, suggesting the method can still differentiate training intensities even if not perfectly accurate.​

RPE appears even less reliable for monitoring resistance exercise dose in older adults, as participants reported nearly identical perceived exertion regardless of actual effort. When possible, objective monitoring tools like velocity-based training devices may provide more accurate autoregulation. If using subjective methods, combine RIR with RPE and recognise that older adults may need additional coaching, feedback, or anchoring sessions (including exposure to true failure) to improve estimation accuracy.

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Key Takeaways

This study found that older adults can consistently underestimate how many repetitions they can perform, particularly when sets get closer to failure. The predicted RIR method may present limited accuracy for precisely prescribing resistance exercise in this population, though it remains somewhat useful for guiding relative training volume. RPE scales showed even less sensitivity, failing to distinguish between different effort levels. These findings challenge the widespread use of subjective intensity measures for resistance training prescription in older adults and suggest that objective monitoring methods or enhanced familiarisation protocols may be necessary to optimise training outcomes.

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Reference

Gómez-Redondo, P., Alcazar, J., Valenzuela, P. L., Ara, I., Alegre, L. M., & Mañas, A. (2025). Validity of repetitions in reserve for prescribing resistance exercise in older adults. Experimental Gerontology, 210, 112884. https://doi.org/10.1016/j.exger.2025.112884

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