This study features one of the largest participant samples we've reviewed in REPS, investigating the ongoing debate on lengthened partials versus full range of motion. While it doesn’t redefine what we know, its findings add to the growing evidence that lengthened partials may be just as effective as full range of motion. Also noteworthy is how the study highlights some shortcomings in standard resistance training research practices.
Overview
- What did they test? A randomized controlled cluster trial across 15 training sites compared full range of motion (ROM) resistance training (n = 134) with lengthened partials (n = 163). Trained participants followed a low-volume, twice-weekly program for 12 weeks. All compound exercises used full ROM, while single-joint exercises for the arms and legs were assigned to either full or partial ROM. Cross-sectional area of the thigh and upper arm was estimated pre- and post-training, while estimated 1RMs were tracked throughout.
- What did they find? The researchers found that both training styles led to small improvements in hypertrophy and strength after 12 weeks of low volume training, with no meaningful advantage for either approach. Changes in estimated muscle size (upper arm and thigh cross-sectional area) and maximal strength (estimated 1RM) were similar between groups, indicating that lengthened partials and full ROM training produced comparable outcomes.
- What does it mean for you? Low-volume training programs that incorporate lengthened partials for isolation exercises are likely to produce similar hypertrophy and strength outcomes as those using full ROM exclusively. If you prefer lengthened partials for comfort, enjoyment, or injury considerations, you can expect comparable outcomes.
What’s the problem?
If you follow exercise science on social media, you’re likely familiar with the ongoing debate between full ROM exercises and lengthened partials (partial reps performed at long muscle lengths). In the November 2024 issue of REPS, we covered a recent preprint by Wolf et al. 1, which compared upper body training using either full ROM or lengthened partials exclusively. The researchers found that both training styles led to small to moderate improvements in muscle thickness and strength-endurance (as measured by 10RM in both conditions). Their results supported the null hypothesis, indicating no meaningful differences between the training styles for muscle growth or strength-endurance.
Research on lengthened partials is still in its early stages, and further studies are needed to clarify their effectiveness. A recent meta-analysis suggested that lengthened partials may actually provide greater hypertrophic benefits compared to full ROM training 2, a finding that wasn’t reflected in the Wolf et al. study. These conflicting results highlight the ongoing uncertainty about whether one method is truly superior. This month’s article adds new data to this discussion.
Beyond this, the authors of the current study highlighted concerns about small sample sizes in resistance training research. They noted that most studies are underpowered, making it difficult to detect meaningful differences between training interventions. Since resistance training interventions typically yield only small effect size changes even when compared to non-training controls, studies with limited sample sizes usually lack the statistical power needed to draw strong conclusions when comparing training methods. To address this, the researchers recruited a large number of participants, aiming to improve the statistical power of their study.
It’s worth noting that this study is a preprint, meaning it has not yet been peer-reviewed or accepted for publication. Therefore, the manuscript reviewed here may undergo revisions before final acceptance.
Purpose
The authors aimed to perform a highly powered investigation, comparing the equivalence of two resistance training interventions, full ROM and lengthened partials, in previously trained participants.
Hypothesis
The authors hypothesized that resistance training using lengthened partials would produce changes in estimated muscle size that are not meaningfully different from those achieved with full ROM training.
