For years, gym culture has been filled with strict rules about “perfect form.” Slow reps. Full range of motion. Never use momentum. Always control the weight. But what if muscle growth is actually more flexible than we thought?
A recent review published in the MDPI journal Journal of Functional Morphology and Kinesiology explored one big question: what exercise technique actually maximises muscle hypertrophy?
The findings challenge a lot of common fitness advice.
The big takeaway
The review concluded that muscle growth appears to depend less on “perfect textbook form” and more on a few key principles:
- Training muscles at longer muscle lengths
- Using a controlled but not excessively slow tempo
- Maintaining enough control to keep tension on the target muscle
- Performing exercises through an effective range of motion
In other words, there may not be one universally “correct” way to lift weights for hypertrophy.
Full range of motion might not be the whole story
Traditionally, fitness professionals have recommended using a full range of motion for every exercise. The review supports this generally, but adds an important nuance.
Research increasingly suggests that training at long muscle lengths may be especially effective for growth.
That means the stretched portion of an exercise could be where much of the hypertrophy stimulus occurs.
Think about:
- The bottom of a squat
- The stretched position in a dumbbell fly
- The lowered phase of a Romanian deadlift
- Deep calf raises
Interestingly, some studies reviewed found that partial reps performed in the stretched position produced similar, or even greater, muscle growth compared to full range movements in certain muscles.
This does not mean full range of motion is useless. Instead, it suggests that where tension occurs during the movement matters more than simply moving from point A to point B.
Do slow reps build more muscle?
One of the most common gym myths is that slower is always better.
The review found little evidence that extremely slow repetitions improve hypertrophy. In fact, very slow training may actually reduce effectiveness in some cases.
Instead, the evidence suggests a fairly broad “effective zone” for repetition speed. The authors recommend total repetition durations between roughly 2–8 seconds.
That means:
- You do not need exaggerated “super slow” reps
- You should still control the weight
- The eccentric (lowering phase) should not simply collapse under gravity
This supports what many experienced lifters intuitively do already: controlled but natural movement.
Is “perfect form” overrated?
Possibly.
The review points out that many exercise technique rules are based more on biomechanics theory and coaching tradition than direct hypertrophy research.
For example:
- How strict should a bicep curl be?
- Is a little body movement automatically bad?
- Does using slight momentum reduce muscle growth?
Surprisingly, there is very little direct research answering these questions.
The authors note that moderate momentum might even help overload muscles in some situations, although excessive cheating likely reduces tension on the target muscle.
The key distinction seems to be whether the target muscle is still doing meaningful work.
What this means in practice
- train muscles through a meaningful stretch rather than only focusing on shortening phases
- keep the weight under control, especially during the lowering portion, without needing to slow everything down excessively
- don’t overthink tempo too much; a steady, natural pace is usually enough
- accept that technique can vary between people depending on body shape, mobility, and experience
- a small amount of natural movement or momentum isn’t automatically a problem if the target muscle is still doing the work
- prioritise whether the exercise actually feels effective and challenging for the muscle you’re trying to train
Final thoughts
What makes this review interesting is that it reflects a broader shift in exercise science.
The conversation is moving away from rigid “one correct way” thinking and toward more flexible, evidence-based principles.
Instead of:
- “Always lift this way”
The emerging perspective is:
- “Does this technique create effective tension for this individual and goal?”
That is a much more nuanced and probably more realistic way to think about training.
Reference
Korakakis, P. A., Wolf, M., Coleman, M., Burke, R., Piñero, A., Nippard, J., & Schoenfeld, B. J. (2024). Optimizing resistance training technique to maximize muscle hypertrophy: A narrative review. Journal of Functional Morphology and Kinesiology, 9(1), 9. https://doi.org/10.3390/jfmk9010009