Partial Reps Don’t Increase Muscle Growth Better than Full Range of Motion in Trained Athletes

Partial Reps Don’t Increase Muscle Growth Better than Full Range of Motion in Trained Athletes Summary

• The study reveals that partial reps (lengthened partial repetitions) produce similar muscle hypertrophy and strength-endurance as full range of motion exercises when performed to muscular failure.
• Unlike many others, the study focuses on trained individuals, showing that partial reps can be effectively incorporated into resistance training routines for similar gains in muscle hypertrophy and strength-endurance.
• This study gives you the freedom to incorporate both full ROM and lengthened partial reps into your routine. Whether you prefer one method over the other, the benefits are the same.

Partial Reps Don’t Increase Muscle Growth the Same as Full Range of Motion?

For years, bodybuilders who didn’t use a full range of motion were often criticized. The claim was simple: using partial reps or “half reps” lifts was thought to be nothing more than a shortcut to lifting more weight without real gains in muscle mass. Experts in the fitness world drilled the idea that a full range of motion was essential for maximizing muscle growth. However, more recent studies challenge that long-held belief half reps using lengthen eccentrics are just as useful.

A new study is catching the attention of athletes and fitness experts alike for its surprising conclusion: performing exercises with lengthened partial repetitions, commonly referred to as partial reps, can yield the same muscle growth as a full range of motion—especially when taken to muscular failure. And perhaps the most groundbreaking aspect? Unlike many previous studies, this study was conducted on trained subjects, which focused on untrained individuals. The study, titled Lengthened Partial Repetitions Elicit Similar Muscular Adaptations as a Full Range of Motion During Resistance Training in Trained Individuals, conducted by Milo Wolf and colleagues, is making headlines in the fitness world. Published in SportRχiv (2024), it challenges some established beliefs about muscle hypertrophy and resistance training¹.

Review of the Literature: Full Range of Motion vs. Lengthened Partial Reps

When it comes to muscle growth, range of motion has long been a topic of debate. Traditionally, the idea has been that full ROM exercises are superior because they involve moving the muscle through its entire length, theoretically engaging more muscle fibers and leading to better hypertrophy. For example, a full bicep curl is believed to be more beneficial than doing partial reps focused only on the lower or upper half of the movement.

However, recent studies suggest otherwise. A 2020 study comparing cable versus barbell preacher curl training revealed that full and partial ROM could produce similar hypertrophic outcomes for the biceps, indicating that exercise selection and execution technique are critical factors in achieving desired hypertrophy.² A 2019 study demonstrated that partial ROM can be just as effective for muscle growth, particularly when focusing on the lengthened phase of the exercise, which places the muscle under greater tension.³ Another study by Kassiano et al. (2022) found that training at longer muscle lengths led to greater hypertrophy compared to shorter muscle lengths, which supports the idea that working in the stretched position can maximize gains.⁴

Moreover, the effects of manipulating the range of motion during resistance training have been studied extensively, mainly focusing on longer muscle lengths. Research comparing longer muscle-length isometric contractions with shorter lengths has shown promising results. For example, five key studies have found that longer muscle lengths produce better hypertrophy results than shorter lengths. ^4-6 Further studies comparing partial reps at longer lengths and shorter lengths support this conclusion, demonstrating that longer-length training results in better hypertrophic outcomes.^7-9

While many of these studies support the effectiveness of partial reps, it’s important to note that most were conducted on untrained subjects. This makes the Wolf et al. study stand out as it addresses explicitly trained individuals, filling a significant gap in the research.

Overview of the Study Protocol: 

The study was conducted with 30 healthy, resistance-trained participants, each with at least six months of consistent upper-body training experience. This is crucial, as muscle adaptations can differ significantly between untrained and trained individuals.

Study Design: A within-participant design was used, meaning that each participant trained one arm using lengthened partial reps and the other arm using a full range of motion. This allowed for direct comparisons within the same individual, minimizing variability in results.

Training Program: The participants followed a multi-exercise, multi-modality training routine over the course of eight weeks. Each week, they completed two training sessions targeting their upper body. Exercises included chest presses, rows, curls, and triceps extensions, with four sets per exercise. Both groups trained to momentary muscular failure, which is known to maximize hypertrophy regardless of the ROM used. Participants were encouraged and closely monitored to ensure they adhered to the specific ROM prescribed for each condition.

Dietary Control: Participants were instructed to maintain their regular diet throughout the study, but nutritional intake was tracked using the MacroFactor app. This helped ensure that changes in muscle mass weren’t due to differences in diet.

What Did the Study Find About Partial Reps?

The results of the study were striking. Muscle thickness and strength improvements were nearly identical between the full ROM and lengthened partial groups. This suggests that the lengthened partial reps were just as effective at stimulating muscle hypertrophy as the full ROM exercises. Improvements in strength-endurance, measured through a 10-repetition maximum (10RM) test, were also comparable between the two groups. Both the full ROM and partial ROM groups showed similar gains in their ability to perform repetitive lifts.

Breaking Down the Results of Partial Reps

The findings of this study challenge the conventional wisdom that full ROM exercises are necessary for maximizing muscle growth. Instead, it suggests that focusing on the lengthened phase of a movement—which occurs when the muscle is under the most tension—may be just as effective. This study provides critical context for the ongoing debate about ROM in resistance training. The results align with other studies demonstrating the benefits of training at longer muscle lengths. For example, a meta-analysis conducted by Wolf et al. (2023) reported a small but meaningful benefit of lengthened partial reps over full ROM training for hypertrophy.¹⁰ This finding highlights that, even in trained individuals, partial reps can be just as effective as full ROM exercises when taken to muscular failure.

Additionally, there seems to be a point of diminishing returns with longer muscle length training. Once muscles are stretched to near-maximal lengths, increasing the ROM further doesn’t necessarily produce more hypertrophy. In the current study, shorter muscle lengths did not enhance muscle growth, suggesting that the lengthened range of motion should be the primary focus during resistance training.

Practical Applications: How to Use Partial Reps for Muscle Growth

What does this mean for your workout routine? The literature suggests that both full range of motion and lengthened partials can effectively contribute to muscle hypertrophy. Still, their efficacy may vary based on several factors, including the specific muscle group targeted, the velocity of contraction, and the overall training protocol employed.If  you’re a bodybuilder or fitness enthusiast aiming for muscle growth, the results of this study provide important insights into how you can structure your training. Here’s how you can apply the findings:

Don’t Fear Half Reps or Partial Reps: If you’ve been told that you need to perform every exercise through a full range of motion, this study suggests otherwise. Lengthened partial reps—other known as half reps particularly those that focus on the stretched phase of the movement—are just as effective as full ROM for muscle hypertrophy. This can be especially useful if you’re recovering from an injury or simply prefer to use heavier weights with half reps. Partial reps are good for muscle growth when taken to failure.

Flexibility in Training: This study gives you the freedom to incorporate both full ROM and lengthened partial reps into your routine. Whether you prefer full or half reps method over the other, the important takeaway is that both are effective as long as you’re pushing yourself to failure.

Apply the Findings to All Muscle Groups: While this study focused on upper-body muscles, the principles can likely be applied to other muscle groups as well. Whether you’re working on your legs, back, or arms, emphasizing the lengthened phase of the movement can help you achieve similar gains without the need for a full range of motion.

Reference:

1               Wolf, M. et al. Lengthened Partial Repetitions Elicit Similar Muscular Adaptations as a Full Range of Motion During Resistance Training in Trained Individuals. (2024).

2               Nunes, J. P. et al. Placing Greater Torque at Shorter or Longer Muscle Lengths? Effects of Cable vs. Barbell Preacher Curl Training on Muscular Strength and Hypertrophy in Young Adults. International Journal of Environmental Research and Public Health 17, 5859 (2020). https://doi.org/10.3390/ijerph17165859

3               Goto, M. et al. Partial Range of Motion Exercise Is Effective for Facilitating Muscle Hypertrophy and Function Through Sustained Intramuscular Hypoxia in Young Trained Men. The Journal of Strength & Conditioning Research 33, 1286-1294 (2019). https://doi.org/10.1519/jsc.0000000000002051

4               Kassiano, W. et al. Greater Gastrocnemius Muscle Hypertrophy After Partial Range of Motion Training Performed at Long Muscle Lengths. J Strength Cond Res 37, 1746-1753 (2023). https://doi.org/10.1519/jsc.0000000000004460

5               Alegre, L. M., Ferri-Morales, A., Rodriguez-Casares, R. & Aguado, X. Effects of isometric training on the knee extensor moment-angle relationship and vastus lateralis muscle architecture. Eur J Appl Physiol 114, 2437-2446 (2014). https://doi.org/10.1007/s00421-014-2967-x

6               Kubo, K. et al. Effects of isometric training at different knee angles on the muscle-tendon complex in vivo. Scand J Med Sci Sports 16, 159-167 (2006). https://doi.org/10.1111/j.1600-0838.2005.00450.x

7               Kassiano, W. et al. Does Varying Resistance Exercises Promote Superior Muscle Hypertrophy and Strength Gains? A Systematic Review. J Strength Cond Res 36, 1753-1762 (2022). https://doi.org/10.1519/jsc.0000000000004258

8               Larsen, S. et al. Resistance training beyond momentary failure: The effects of lengthened supersets on muscle hypertrophy in the gastrocnemius. (2024).

9               Maeo, S. et al. Greater Hamstrings Muscle Hypertrophy but Similar Damage Protection after Training at Long versus Short Muscle Lengths. Med Sci Sports Exerc 53, 825-837 (2021). https://doi.org/10.1249/mss.0000000000002523

10            Wolf, M., Androulakis-Korakakis, P., Fisher, J., Schoenfeld, B. & Steele, J. Partial vs full range of motion resistance training: A systematic review and meta- analysis. (2022).