Lengthened partials vs. full range of motion: What the latest research says about muscle growth

Lengthened partial repetitions—reps performed in the stretched position of an exercise and often taken beyond momentary failure—have gained considerable attention in the fitness community over the past few years. Promoted as a strategy to enhance muscle growth, these techniques are frequently highlighted in social media posts and hypertrophy discussions.

A newly released preprint study provides fresh data comparing the effects of lengthened partials (LP) and full range of motion (ROM) training with added partials on muscle hypertrophy in resistance-trained individuals. This article reviews the study’s methods, findings, and implications for program design.

Previous research by the same group of investigators examined the effects of lengthened partial supersets (LPSS)—repetitions performed in the stretched position beyond failure—on muscle growth in untrained individuals. In that study, participants in the LPSS condition experienced an average increase of 0.19 cm in medial gastrocnemius thickness, compared to 0.14 cm in the full ROM condition.²

Although the absolute difference in growth was only 0.05 cm, the result was heavily amplified online, with claims of “43% more muscle growth” in the LP group. While technically accurate in relative terms, this reporting was misleading given the small magnitude of change. The observed difference is unlikely to be practically meaningful and warrants further investigation in trained individuals.

The most recent study by Larsen et al.¹ sought to address this gap by examining the effects of lengthened partials in a more experienced population. The study included 23 resistance-trained individuals, defined as participants who had performed at least two resistance training sessions per week for the previous three years.

Researchers employed a within-subjects design, where each participant trained both legs separately under different conditions: