The Hornberger Lab

Lengthened partial repetitions have received considerable attention as a strategy for maximizing muscle hypertrophy. Most research indicates that the lengthened portion of a rep is more hypertrophic than the shortened portion. But research comparing lengthened partials vs full ROM training have produced mixed results. A new study from @drmikeroberts lab, led by Daniel Plotkin, sheds additional light on the topic (PMID: 42841600). The study employed a within-subject design in resistance-trained men, with one leg assigned to lengthened partials and the other to full ROM. Training was performed twice weekly using leg presses, leg extensions, and lying leg curls for 8 weeks. Whole muscle growth was assessed using MRI and fiber type growth assessed by biopsy. Results showed both conditions promoted appreciable growth of the vastus lateralis, with no clear difference between conditions in CSA or fiber type hypertrophy. Moreover, both protocols produced broadly similar changes in anabolic signaling and gene expression following exercise. Notably, these findings were only a portion of the overall study, which also included MRI of the lower body muscles. Based on the preprint, quad and glute hypertrophy was similar between conditions. Interestingly, however, lengthened partials showed a tendency to produce greater overall hamstring hypertrophy, largely driven by greater growth of the semitendinosus. This suggests that the effects of ROM manipulation may be muscle- and exercise-specific. From a practical standpoint, these findings challenge the notion that lengthened partials are universally superior to full ROM training for hypertrophy—consistent with a study from our lab on the topic (PMID: 39959841), amongst others. Both approaches appear capable of producing meaningful muscle growth, even in experienced lifters. However, the potential advantages of lengthened partials may depend on the specific muscle and exercise being trained. Bottom Line: Rather than establishing one approach as universally superior, the emerging evidence suggests that the hypertrophic benefits of different ROM strategies may be muscle-specific. It is also conceivable that combining approaches could produce complementary, or perhaps even synergistic, hypertrophic adaptations. Moreover, given the joint-angle specificity of strength adaptations, incorporating a substantial amount of full ROM training would seem prudent to maximize the overall benefits of resistance training. pubmed.ncbi.nlm.nih.gov/4284…

Why do some people gain more muscle than others? Last year I participated in the 2025 Inter-Individual Variation in Resistance Training Response Conference at the University of Jyväskylä, organized by @DrMikeRoberts, where leading researchers discussed why hypertrophy responses can vary so widely between individuals. The findings were summarized in a recent paper published in JAP (PMID: 42172438) Some key takeaways: --Programming matters. Evidence suggests ~10 sets per muscle per week is sufficient to efficiently promote hypertrophy for most people, with diminishing returns as volume increases. Rest periods should generally be at least 60 seconds—and ≥2 minutes for multi-joint exercises—with sets performed close to failure (~2 RIR or less). --“Non-responders” may not really be non-responders. A single pre/post measurement can reflect measurement error and normal biological variation rather than someone's true response to training. --Genetics aren't destiny. Despite substantial variability in muscle growth, we currently lack strong evidence that genetic testing can meaningfully predict who will or won't respond well to resistance training. Hypertrophy appears to result from a complex interaction of numerous biological and environmental factors. --Age doesn't automatically make you a poor responder. Some older adults respond very well to resistance training, and chronological age alone shouldn’t be viewed as a barrier to gaining muscle. Resistance training remains a potent strategy for combating age-related declines in muscle mass and strength. --Before blaming your biology, get the basics right. If progress is poor, first examine training consistency, progressive overload, sleep, and dietary habits. Supplements play a comparatively minor role in muscle-building. Bottom Line: Yes, people differ in how much muscle they gain from resistance training—but determining someone's true responsiveness is far more complicated than labeling them a “high responder” or “non-responder.” The most important controllable factor remains remarkably straightforward: Train consistently, apply progressive overload, and keep doing it for the long haul. journals.physiology.org/doi/…

New study shows that partial range of motion in the leg extension at long muscle lengths elicits greater hypertrophy compared to training at short muscle lengths. Moreover, gains for the long length condition were generally comparable to training through a full ROM. These findings are consistent with the growing body of evidence suggesting that the lengthened portion of a repetition provides the strongest stimulus for muscle hypertrophy. Nice work from @MuscleMechsLab 💪 pubmed.ncbi.nlm.nih.gov/4239…