Comparing First- and Last-Repetition RPE for Intensity Monitoring in Elastic Resistance Training: A 16-Week Randomized Controlled Trial in Older Adults

Background: The timing of perceived exertion assessment within a resistance training set may influence physiological adaptation; this study aimed to directly compare first-repetition (RPE-1) and last-repetition (RPE-last) monitoring strategies applied to functional, neuromuscular, body composition, and cardiometabolic adaptations during elastic band resistance training in older adults. Methods: Forty sedentary older adults (n = twenty per group, sex-balanced) were randomly assigned to RPE-1 or RPE-last using the OMNI-RES elastic band scale during a 16-week, open-label high-intensity elastic band resistance training program, with blinded outcome assessment and data analysis; three withdrew during the intervention (RPE-1, n = 2; RPE-last, n = 1), and all forty randomized participants were retained in the intention-to-treat analysis via baseline carry-forward. Functional capacity, isokinetic knee and elbow strength (60 and 180°/s), DXA-assessed body composition, and fasting cardiometabolic biomarkers were evaluated pre- and post-intervention. Between-group effects were analyzed using ANCOVA with Benjamini–Hochberg false discovery rate (FDR) correction, whereas functional equivalence was assessed using Welch-corrected two one-sided tests (TOST) with percentile bootstrap against published minimum clinically important difference (MCID) margins. Results: Both groups improved significantly across most outcomes. For the primary outcomes, RPE-1 was associated with greater improvements across all eight isokinetic strength conditions after FDR correction, with adjusted between-group differences ranging from +7.86 to +18.38 Nm in favor of RPE-1, and all 95% CIs excluding zero (ηp2 = 0.14–0.37). The Welch-corrected TOST demonstrated functional equivalence between monitoring strategies for all four functional outcomes in the primary intention-to-treat analysis. However, the pre-specified complete-case sensitivity did not confirm equivalence in the 30-Second Chair Stand Test, indicating that this outcome was sensitive to the handling of missing data. Among secondary exploratory outcomes, RPE-1 also was associated with greater improvements in DXA-assessed fat mass (adjusted difference—−1.33 kg; 95% CI—−2.02 to −0.63; ηp2 = 0.29) and lean mass (+0.42 kg; 95% CI—0.02 to 0.83; ηp2 = 0.11), high-density lipoprotein cholesterol (+5.11 mg/dL; 95% CI—1.52 to 8.69; ηp2 = 0.18), and low-density lipoprotein cholesterol (−16.99 mg/dL; 95% CI—−23.22 to −10.76; ηp2 = 0.45). Conclusion: RPE-1 appeared to confer greater benefits for maximizing neuromuscular strength, whereas RPE-last provides an equally valid alternative when preserving physical independence is the primary objective.