Trainability of Repetitions-in-Reserve Estimation in Younger and Older Adults

Effort-based resistance training (RT) approaches, such as repetitions in reserve (RIR), aim to enhance RT individualization, which is of particular relevance for older adults. However, evidence on the accuracy of RIR estimation and its trainability, particularly in older adults, is limited. Accordingly, this study aimed to (I) compare RIR estimation accuracy during bench press and leg press between younger and older adults, and (II) determine whether six consecutive training sessions can meaningfully improve estimation in both groups. Therefore, thirteen younger adults (33±7 years; 9 females, 4 males) and thirteen older adults (67±4 years; 7 females, 6 males), completed six sessions across six weeks. Each session comprised three sets per exercise at randomized loads (75%-85% one repetition maximum). During each set, participants verbally indicated the repetition (rep) at which they estimated having 4 and 2 RIR (4RIR, 2RIR) and then continued the set to concentric muscle failure.