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.

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

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.

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Practical Applications for Enhanced Muscle Growth

For those looking to incorporate these findings into their training routines, here are some practical takeaways:

1. Incorporate Lengthened Partials: Adding lengthened partials after reaching full ROM failure in your sets can lead to greater muscle growth, particularly in exercises like calf raises where the movement is hardest at the top.
2. Focus on Stretched Positions: Training muscles in their stretched positions seems to promote hypertrophy more effectively. For calf exercises, standing calf raises with knees extended, which lengthen the gastrocnemius, are particularly beneficial. For the soleus, since it doesn’t insert at the knee, any calf raise will work well, though there might be a very slight edge to a seated calf raise over a standing calf raise.
3. Experiment with Lengthened Supersets: If lengthened partials are not appealing, lengthened supersets offer an alternative way to emphasise the muscle stretch and potentially increase growth. This involves doing some partial reps in the stretched position after reaching full ROM failure.

Source: Andrea Piacquadio on Pexels

The recent study by Larsen highlights the potential benefits of incorporating lengthened partials after full range of motion failure into your training regimen. The findings suggest that this method can lead to greater muscle hypertrophy, particularly in the gastrocnemius muscle of the calf. While more research is needed to generalise these results to other muscles and exercises, the evidence indicates a promising approach for those seeking to maximise their muscle growth. By integrating lengthened partials or supersets into your routine, and focusing on exercises that challenge the muscle in its stretched position, you can potentially enhance your gains and achieve better results in your fitness journey.

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