Resistance 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 calf training with initial partial repetitions versus full range-of-motion (ROM) repetitions followed by past-failure partials on gastrocnemius hypertrophy. Twenty-three participants (men: n = 16 and women: n = 7) performed four sets of unilateral Smith machine calf raises to momentary failure twice a week for 8 weeks. One leg was trained using initial partials to their individualized maximum dorsiflexion ROM. The contralateral leg was trained with a full ROM and continued with past-failure partials after failure in peak plantarflexion. Medial gastrocnemius muscle thickness was measured with ultrasonography both baseline and postintervention. A Bayesian framework was used to estimate the average treatment effect (ATE) using credible intervals and Bayes factors (BFs). 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 gastrocnemius hypertrophy. Although the average change favored initial partials, the estimated difference was uncertain, and the Bayes factor provided only anecdotal support for a differential effect.

Keywords: calves; muscle length; muscle thickness; plantarflexion; ultrasonography.

FIGURE 1

Consort diagram illustrating the data collection process. The enrollment process was similar to Larsen et al. (2025).

FIGURE 2

Illustrates the plantarflexion ROM for the (A) initial partials and (B) past‐failure partial legs, respectively.

FIGURE 3

Comparative distribution plot of estimated standardized mean difference of interventions. Density plots illustrate estimates and uncertainty of standardized mean difference changes across the two interventions. Thresholds describing the magnitude of improvements are obtained from strength and conditioning‐specific data.

FIGURE 4

Mean (SD) volume load (sets × load × repetitions) lifted each resistance training session for the initial partials and past‐failure partials leg. LP = lengthened partials; PFP = past‐failure partials; RT = resistance training.