Stretching the Muscle for Muscle Growth Myths Debunked |

A new preprint study from the University of British Columbia challenges the popular belief that stretching the muscle for muscle growth leads to superior results. Over ten weeks, participants trained using both “stretch-focused” and “squeeze-focused” resistance profiles. Researchers found that both methods produced similar gains in muscle size and strength, suggesting that the key factor for growth is training effort and consistency rather than where peak tension occurs. The findings indicate that while stretching the muscle under load for hypertrophy can be beneficial, it isn’t necessarily more effective than traditional training. For most lifters—especially beginners—focusing on full range of motion, intensity, and progressive overload remains the most reliable approach. In short, the study concludes that stretch focused training vs traditional lifting for muscle size results in comparable outcomes, emphasizing that consistent, challenging workouts drive real muscle growth, not just the stretch position of an exercise.

Stretch vs Squeeze: New Research Questions Whether Stretching a Muscle Really Builds More Muscle Key Takeaways

A new preprint study from the University of British Columbia found that training at longer muscle lengths didn’t lead to more muscle growth than training at shorter muscle lengths. This challenges common beliefs about stretching the muscle for muscle growth and how it affects training results.
Both “stretch-focused” and “squeeze-focused” training led to similar gains in muscle size and strength after 10 weeks.
For untrained individuals, simply training hard and consistently matters more than where peak resistance occurs.

Rethinking Stretching the Muscle for Muscle Growth

For the past year, social media has been buzzing with one bold claim: “Stretching the muscle builds more muscle.” Coaches and influencers alike have been telling lifters to train in the “stretched position”—think incline curls, deep squats, and Romanian deadlifts—to unlock “superior hypertrophy.”

But what if that’s not the full story?

A new preprint study (not yet peer-reviewed) from researchers at The University of British Columbia, titled “Stretch vs Squeeze: The Impact of Varying Resistance Challenge at Long vs Short Muscle Lengths. A Randomized Controlled Trial” (Jones et al., 2025), challenges this trendy idea.

This 10-week experiment found that loading a muscle in its stretched position — what scientists call the “descending limb” of the length-tension curve — didn’t lead to greater muscle growth than training in the shortened position.

In simpler terms, stretching the muscle under load didn’t produce better gains than squeezing it.

Review of the Literature: Does Stretching the Muscle for Muscle Growth Really Work?

Let’s take a quick step back.

For years, research has suggested that training at longer muscle lengths may lead to greater growth. Studies on the hamstrings, calves, triceps, and biceps have often found that exercises performed when the muscle is stretched — such as seated leg curls or incline curls — can lead to slightly greater hypertrophy.^1-3

However, these studies weren’t perfect. Many compared different exercises that varied not only in muscle length but also in other factors, such as range of motion, resistance profile, and overall tension curve. So, it was hard to tell whether the stretch itself was driving the superior growth, or something else entirely.

That’s what makes this new research so interesting. The team at UBC designed a study that directly controlled for those variables — same range of motion, same exercise type, same effort — with the only difference being where the muscle experienced the hardest part of the lift.

Study Design: How They Tested Stretching the Muscle for Muscle Growth

Twenty untrained young adults (7 men and 13 women, aged 19–30) participated in the 10-week trial. Each participant trained two times per week, performing four exercises designed to hit both the upper and lower body:

Reverse fly for the rear shoulders
Chest fly for the chest
Lateral raise for the side delts
Multi-hip machine for the glutes

Each participant’s left and right limbs were randomly assigned to one of two conditions:

Descending bias (Stretch-focused): Peak resistance occurred when the muscle was lengthened — for example, the bottom of a chest fly.
Ascending bias (Squeeze-focused): Peak resistance occurred when the muscle was shortened — for example, the top of a chest fly.

Every set was taken to momentary muscular failure (the point where you can’t complete another rep with good form) using moderate weights — roughly 70% of their one-rep max — for 4–5 sets of 8–12 reps.

Both sides of the body were trained identically in terms of effort, rest, and range of motion.

Measuring Growth

To get precise data, researchers used 3-Tesla MRI scans (a high-resolution imaging technique) to measure muscle growth before and after the training period. They scanned the posterior and lateral deltoids, the pectoralis major (chest), and the gluteus maximus. Muscle cross-sectional area (how thick the muscle became) and volume were analyzed using specialized imaging software.

Results: What Happens When You Focus on Stretching the Muscle for Muscle Growth

After 10 weeks, both training styles led to significant muscle growth. Here’s what they found:

Posterior Deltoid: Increased by about 15–26%, with no difference between groups.
Lateral Deltoid: Grew by 18–20%, again, no difference.
Pectoralis Major: Grew by 17–19%, no difference.
Gluteus Maximus: Increased muscle volume by about 6%, no difference.

Strength (measured by one-rep max tests) also improved across all exercises — roughly 17–20 kilograms (37–44 pounds) more on the chest fly and reverse fly, and 13–15 kilograms (29–33 pounds) more on the lateral raise. But again, both the stretch and squeeze conditions improved equally.

In short: both groups got stronger and bigger, but neither method outperformed the other.

The authors concluded that “biasing peak torque toward longer muscle lengths does not enhance hypertrophy beyond that achieved with shorter-length bias in previously untrained adults.⁴

Discussion: What These Results Mean for Stretch Mediated Muscle Growth

So, what does this mean for your training?

If you’ve been stressing over whether you should “stretch the muscle under load,” relax — both methods work. The results suggest that as long as you’re training hard, close to failure, and with a full range of motion, your muscles will grow.

This doesn’t mean the stretch-focused method is useless. Many lifters might still feel better activation or comfort using one profile over the other. The “stretch” part of a lift can certainly be beneficial for mobility and joint control. But this study shows that in untrained individuals, simply pushing yourself hard is the bigger driver of growth — not necessarily where the muscle is challenged.

Why might that be?

Newbie gains: Untrained participants often experience rapid muscle growth regardless of the exact program, as almost any stimulus is new and effective.
Effort is king: Both groups trained to true muscular failure — a critical factor for growth.
Controlled volume and ROM: Because the range of motion and total work were matched, there wasn’t room for one method to “win” simply due to more overall effort.

It’s also worth noting that this is a preprint study — meaning it hasn’t yet been peer-reviewed. Results could change after additional analysis or replication in trained lifters. Still, the design was rigorous and adds a valuable piece to the conversation.

Practical Applications

So, how can you use this information?

Train hard — not just “stretched.” Don’t overcomplicate things. Whether you’re feeling the burn at the bottom or top of a lift, what matters most is reaching muscular failure safely and consistently.
Full range of motion still matters. The study controlled for range of motion, meaning both groups trained through a full range of motion. That’s important for balanced development and joint health.
Program variety is your friend. You don’t need to choose between “stretch” and “squeeze.” Mixing exercises that challenge different parts of the range of motion — like combining incline curls and preacher curls — might still be a great way to target a muscle fully.
Beginners: focus on consistency. If you’re new to lifting, this study suggests that how hard you train and how often you show up matters far more than fancy biomechanical tweaks.
Trained lifters, stay tuned. Future research should test these methods in advanced athletes who might respond differently once the “beginner effect” wears off.

Practical Applications: How to Use Stretching the Muscle for Muscle Growth in Training

The hype around “stretch-mediated hypertrophy” might have gotten a bit ahead of the evidence. According to this new preprint study from UBC, training at longer muscle lengths doesn’t automatically mean more muscle growth — at least not for untrained individuals.

The real takeaway? Don’t get caught up in the stretch-vs-squeeze debate. Just train with intention, control your range, and challenge your muscles close to failure. That’s what builds real, lasting gains.

Because at the end of the day — it’s not about where the tension peaks. It’s about how hard you push when it does.

References

1 Maeo, S. et al. Triceps brachii hypertrophy is substantially greater after elbow extension training performed in the overhead versus neutral arm position. Eur J Sport Sci 23, 1240-1250 (2023). https://doi.org/10.1080/17461391.2022.2100279

2 Pedrosa, G. F. et al. Partial range of motion training elicits favorable improvements in muscular adaptations when carried out at long muscle lengths. Eur J Sport Sci 22, 1250-1260 (2022). https://doi.org/10.1080/17461391.2021.1927199

3 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

4 Jones, A. et al. Stretch vs Squeeze: The Impact of Varying Resistance Challenge at Long vs Short Muscle Lengths. A Randomized Controlled Trial. (2025).