Research Claims Lengthened Partial Reps Better than Full Range of Motion for Muscle Growth

Muscle hypertrophy is a topic of immense interest among fitness enthusiasts, trainers, and researchers. Recently, a study by Larsen et al. (2024) shed light on a new approach that could potentially enhance muscle growth: performing lengthened partial reps after reaching full range of motion (ROM) failure.

Here we will dive into the specifics of this study, exploring its methodology, findings, and practical applications for those looking to maximise their muscle growth, particularly in the calf muscles.

The contents of this article are largely based on a newsletter from Stronger by Science and written by Milo Wolf. Dr Milo Wolf shares his invaluable knowledge on a YouTube channel ranging from hypertrophy and strength training to losing fat. It is also important to note that Milo Wolf was one of the authors of the research we are basing the information for this article.

The study focused on the effects of lengthened partials past failure compared to terminating the set at full ROM failure. Using a within-participant design, 22 untrained participants engaged in a 10-week training programme involving single-leg Smith machine calf raises. Each participant’s limbs were trained differently; one limb ceased training upon reaching full ROM failure, while the other limb continued with partials until volitional failure or until movement from the fully stretched position was impossible. This innovative approach aimed to test whether continuing with partials after full ROM failure could stimulate greater muscle growth.

The researchers manipulated the set endpoint to understand the impact on hypertrophy better. Calf raises typically become challenging at the top of the movement, where the muscle is fully contracted. Since previous evidence suggests that training at longer muscle lengths might be more effective for muscle growth, this study hypothesised that extending the set with partials could yield better results. The study’s findings could have significant implications for muscle growth strategies, especially for exercises that are hardest in their peak contraction.

The study by Larsen et al. (2024) measured increases in muscle thickness of the gastrocnemius, a major calf muscle. The results indicated that performing lengthened partials led to approximately 40% greater hypertrophy compared to just full ROM training. This aligns with previous studies, such as those by Kassiano and colleagues, who found that lengthened partials resulted in significantly more muscle growth than both full ROM and shortened partials in leg press calf raises. The consistency of these findings across different studies suggests a robust potential for lengthened partials to enhance muscle hypertrophy.

The key takeaway from this study is the apparent superiority of lengthened partials over traditional full ROM training. The additional muscle growth observed could be attributed to several factors: the lengthened position of the muscle during partials, the extended time under tension, and the increased overall volume load. However, it remains challenging to isolate the exact cause of the additional hypertrophy due to the interplay of these variables.