Training beyond momentary failure: The effects of past-failure partials versus initial partials on calf muscle hypertrophy among a resistance-trained cohort

Abstract

This study compared the effects of plantar flexion training with initial partial repetitions versus full range-of-motion (ROM) repetitions followed by past-failure partials on gastrocnemius muscle thickness in resistance-trained individuals. Twenty-three participants performed four sets of unilateral Smith machine calf raises to momentary failure twice a week for eight weeks. One leg was trained using initial partials to their individualized maximum dorsiflexion ROM (-29.8 ± 5.9° to 0°). The contralateral leg was trained with a full ROM (-31 ± 6.8° to +33.6 ± 7.8°) and continued with past-failure partials after momentary failure in peak plantarflexion. Medial gastrocnemius muscle thickness was measured with B-mode ultrasonography at both baseline and post-intervention. A Bayesian framework was used to estimate the average treatment effect (ATE) and assess our a priori hypothesis of the superiority of initial partials using credible intervals and Bayes Factors (BF). The ATE posterior distribution indicated a greater increase in muscle hypertrophy for the initial partial condition (0.40 [95%CrI: -0.06 to 0.85 mm]; p(>0)=0.958), with a BF of 1.2 suggesting ‘anecdotal’ evidence in favor of an effect. Within-condition analyses using standardized mean difference estimates indicated that the interventions were likely to produce medium to large improvements. These findings suggest that both initial partials and past-failure partials are viable strategies for achieving medial gastrocnemius hypertrophy in resistance-trained individuals. Although the average change favored initial partials, the estimated difference was uncertain, and the Bayes Factor provided only anecdotal support for a differential effect. Further research with longer interventions is needed to clarify whether one method is truly superior.