Accurate prescription and monitoring of resistance training (RT) load require ensuring that the external load prescribed by the coach reflects the internal demands experienced by the athlete. Although repetitions in reserve (RIR) have been proposed as a practical method for quantifying proximity to failure, their use in isolation assumes that identical RIR values correspond to equivalent physiological stimuli across different repetition ranges and intensities. This assumption does not necessarily reflect comparable internal loading conditions. To address this limitation, the concept of “level of effort”—defined as the “relationship between the repetitions performed and the maximum number of repetitions that could be completed with a given load”—offers a proportion-based and more comprehensive representation of exertion. When quantified through movement velocity, the level of effort integrates two critical variables: relative intensity (via the fastest repetition velocity) and fatigue development (via velocity loss), allowing accurate estimation of the percentage of repetition capacity utilized within a set. This approach enables practitioners to derive RIR from an objective measure of actual effort, thereby enhancing the precision of RT prescription and monitoring.