Plus 3 training applications to maximize hypertrophy
Key Points You Need To Know:
Maximum biceps growth, especially fuller size near the elbow, occurs with curls.
Rows are still great for overall back development and will hit the biceps somewhat, but they may not maximize distal biceps hypertrophy (near the elbow)
Don’t rely on the “pump” alone: The study showed acute swelling patterns didn’t perfectly match hypertrophy outcomes.
Best strategy? Use exercise variation by combining single-joint (curls) and multi-joint (rows, pull-ups, pulldowns) for balanced development and efficiency.
The quest for the best exercises to maximize muscle growth is never-ending. You can easily find articles titled “Top 5 Exercises For (any muscle you want)”. But what if we have it wrong? What if the best way to maximize muscle hypertrophy isn’t using the best exercise, but by using multiple exercises? That’s what new research published in Sport Sciences for Health suggests, adding to the growing stack of literature promoting exercise variation over using a single exercise.
The Study: Acute and chronic regional changes in elbow flexor thickness after resistance training with dumbbell curl or dumbbell row exercises (2025)
A 2025 study in Sport Sciences for Health (Leitão et al., 2025) wanted to answer a couple of questions concerning bicep growth:
Are there differences between acute and long-term muscle growth from resistance training?
Do dumbbell curls or rows produce greater muscle hypertrophy?
Does using multiple exercises produce greater muscle growth than a single exercise?
To do this, they compared single-joint dumbbell curls (DC) and multi-joint dumbbell rows (DR) to see how each exercise affects muscle growth in the biceps.
How Did Researchers Compare Differences in the Biceps’ Muscle Growth?
Since the researchers were looking at both chronic and acute effects, they used two studies.
Each study used a similar protocol with a within-subject experimental design. Each participant performed a dumbbell curl with one arm and a single-arm row with the other.
Muscle hypertrophy was measured at proximal (25%) and distal (75%) regions of the biceps.
Experiment 1 (Acute response): To determine acute response, 16 trained men performed a single session of dumbbell curls and single arm dumbbell rows using a 4×8–12RM rep scheme.
Ultrasound was used to measure muscle swelling immediately after training (a temporary increase in thickness).
Experiment 2 (Chronic adaptation): To look at long-term growth, nine untrained men trained for 8 weeks, twice per week, performing curls with one arm and rows with the other. Muscle thickness was measured before and after training at two points along the biceps (proximal = near the shoulder; distal = near the elbow).
What’s The Difference Between Acute And Chronic Muscle Growth?
Let’s touch on “acute” and “chronic” muscle hypertrophy and why that matters.
Acute Effects was the immediate swelling of the biceps measured right after a workout. This is casually referred to as “the pump,” caused by blood flow and water accumulation.
Chronic Effects were measured after eight weeks of training, reflecting true muscle hypertrophy from long-term adaptation. This is “actual growth” that will stick around.
The acute swelling can highlight which regions of a muscle are most stressed during an exercise in real time. However, only chronic measurements confirm whether that stress actually translates into lasting growth.
This distinction is crucial in today’s gym, where many lifters are chasing the pump. They confuse their larger muscles after an intense session with actual growth, but a few days later, they find out their muscles have “shrunk”.
Now, this doesn’t mean the pump has no value, as there is a relationship with muscle growth, and it can be anabolic. However, it’s important to distinguish the difference and that training for a pump doesn’t automatically translate into real muscle growth.
What Did The Researchers Find?
Alright, so what happened? Here’s a rundown of the results.
Acute (single session):
Both curls and rows caused swelling along the biceps.
Curls produced greater swelling proximally (nearer the shoulder) than rows (19% vs 13%).
Distal swelling (near the elbow) was similar between exercises.
Chronic (8 weeks of training):
Dumbbell curls increased muscle thickness both proximal (≈5%) and distal (≈11%).
Dumbbell rows increased only proximal thickness (≈5%), with no significant distal growth (≈1%).
Overall, curls produced more total hypertrophy, especially in the lower (distal) biceps region.
In the acute experiment, the dumbbell curls produced greater growth in the entire biceps. Of interest, this growth was significantly greater in the proximal region of the biceps (near the shoulders).
In the chronic experiment, the dumbbell curls again produced greater overall growth. Of interest, both groups produced similar increases in the proximal region of the biceps. However, in the distal region (near the elbow), the row saw minimal growth while the bicep curls produced an 11% increase in muscle.
Why Might This Happen?
So, why would these two exercises cause such differences? Well, there are 3 things to consider.
1. Range of motion: Range of motion (ROM) plays a large part in muscle growth, with greater ROM generally being ideal for growth. This is largely due to:
The amount of tension placed on the muscle
A more even distribution of tension throughout the muscle belly
Curls train the biceps through a larger range of motion, resulting in greater stretch and more direct tension along the length of the muscle.
2. Exercise mechanics: In rows, the biceps assist the back and shoulder muscles rather than being the prime mover. This could limit their hypertrophic stimulus or even focus.
When an individual performs a curl, their focus is likely directed more to the biceps muscle. Theoretically, this could invoke the mind-muscle connection, which has been found to be a determinant in muscle growth (Calatayud et. al, 2017)
3. Regional differences: Evidence now shows that a muscle (like the biceps or rectus femoris) can grow more in specific regions depending on the exercise mechanics.
Numerous studies have shown that when using a single exercise, the working muscle will experience different amounts of growth in areas that experience more stress (Antonio, 2000).
How This Compares To Other Research
The results of this study align with other research, but they need to be considered in context.
1. The effect of muscle swelling and its relationship to long-term muscle growth is surprisingly largely understudied.
There was an interesting study in 2022 published in the Journal of Strength and Conditioning Research that looked at the association between the muscle swelling after the first training session of a 6-week program and muscle growth at the end. Unlike this study, they did find a direct relationship.
While interesting, this is mechanistic and shouldn’t affect our training significantly.
2. In terms of the non-uniform growth seen in a muscle, there has been a lot of research in the past that lines up with these findings. So much so that we would say, to optimize growth, it’s essential to use exercise variation.
This opinion is echoed by Dr. Jose Antonio, who published a study in the Journal of Strength and Conditioning Research. He conducted a study researching the effect of several exercises on muscle activation and growth. Due to non-uniform muscle growth from a single exercise, he concluded;
“…no single exercise can maximize the hypertrophic response of all regions of a particular muscle…for maximal hypertrophy…athletes (particularly bodybuilders) are justified in incorporating various exercises.“
Another study from de Vasconcelos et. al (2021) published in the International Journal of Sports Medicine examined using a single exercise to train the biceps and quadriceps or a variety (3 exercises). In it, both the biceps and quadriceps saw fuller muscle growth across the entire muscle compared to using a single exercise.
We have written about this before in a dedicated article, so be sure to check that out!
What Does This Mean For Your Training?
When looking at the takeaways, it’s important to note that the muscle swelling is mechanistic in nature, while using exercise variation is directly applicable to our training.
So, while looking for the relationship between acute swelling and long-term growth is definitely interesting, “chasing the pump” probably isn’t the best take-away.
Rather, this study shows the important roles that exercise selection and exercise variation choice can play in our overall training method.
Now, since only one isolation and one compound exercise were tested, we obviously can’t apply this to all movements. For example, chin-ups and close-grip lat pulldowns are excellent bicep exercises.
The most practical conclusion is that variation of exercises that mix compounds and isolations is likely needed to optimize muscle growth.
With that said, be sure to include exercise variation in your training following these 3 guidelines.
1. Don’t use exercises with similar biomechanics in the same session. This can become redundant as the muscles are being worked in the same way.
Don’t Use: Bench press and push-ups
Use: Incline bench press, dips, chest flies
2. If you train the same muscle twice a week, use different exercises. This can vary depending on the individual and training goals, but here’s an example of how it might look.
Session 1: Incline barbell bench press, chest flies
Session 2: Dumbbell flat bench, dips
3. Alter exercises in a systematic approach. You still need to concentrate on applying progressive overload, which requires using the same exercises. The time frame can vary greatly depending on your training age, but here are some general recommendations;
Large exercises: Swap every 6-12 weeks
Accessory exercises: Swap every 2-4 weeks
Isolations: You can alter every session or two if you want
Keep in mind these are general guidelines, and specifics depend on the person. Regardless, remember to always train smarter, not harder!
References
Antonio, J. (2000). Nonuniform response of skeletal muscle to heavy resistance training: Can bodybuilders induce regional muscle hypertrophy? Journal of Strength and Conditioning Research, 14(1), 102–113. https://doi.org/10.1519/00124278-200002000-00017
Calatayud, J., Vinstrup, J., Jakobsen, M. D., Sundstrup, E., Brandt, M., Jay, K., … Andersen, L. L. (2017). Mind–muscle connection training principle: Influence of muscle strength and training experience during a pushing movement. European Journal of Applied Physiology, 117(7), 1445–1452. https://doi.org/10.1007/s00421-017-3637-6
de Vasconcelos Costa, B. D., Kassiano, W., Nunes, J. P., Kunevaliki, G., Castro-E-Souza, P., Rodacki, A., Cyrino, L. T., Cyrino, E. S., & de Sousa Fortes, L. (2021). Does performing different resistance exercises for the same muscle group induce non-homogeneous hypertrophy? International Journal of Sports Medicine, 42(9), 803–811. https://doi.org/10.1055/a-1308-3674
Hirono, T., et al. (2022). Relationship between muscle swelling and hypertrophy induced by resistance training. Journal of Strength and Conditioning Research, 36(2), 359-364. https://doi.org/10.1519/JSC.0000000000003478
Leitão B. F. M., Albarello J. C. S., Halmenschlager G. H., Mannarino P., Nunes J. P., De Salles B. F., & Matta T. T. (2025). Acute and chronic regional changes in elbow flexor thickness after resistance training with dumbbell curl or dumbbell row exercises. Sport Sciences for Health. https://doi.org/10.1007/s11332-025-01530-7
