Skip to main content

Can doing bicep curls on one arm boost strength in the other? Study finds out

Is it possible that doing bicep curls with your left arm somehow impacts the muscles in your right arm?

Muscular man bicep curling weight in one hand
Anush Gorak / Pexels

When you’re only curling a dumbbell with one arm, you might think the other arm just hangs out, unaffected. In a fascinating new study, researchers set out to explore whether only training one arm would affect muscle strength and size in the other when we don’t train that side. Is it possible that doing bicep curls with your left arm somehow impacts the muscles in your right arm? Let’s take a look at the research. 

The study

workout recovery, man doing bicep curls
Pressmaster / Adobe Stock

In a study published in The Scandinavian Journal of Medicine & Science in Sports, researchers wanted to understand whether unilateral or single-limb training with heavy weights impacted the strength in the non-working arm. The focus was on neural adaptations and muscle strength and size. 

Recommended Videos

The study methods

man doing bicep curl in gym one arm unilateral dumbbell.
Tima Miroshnichenko / Pexels

The study involved 160 healthy younger adults who hadn’t done any resistance training in the last six months. Researchers measured muscle thickness and strength at the start and end of the study. They assigned the participants into one of four different groups:

  • Control group — No training.
  • D + ND — Training both arms.
  • D only — Training only the dominant arm.
  • ND only — Training only the non-dominant arm.

Over six weeks, study participants finished three training sessions every week for a total of 18 bicep curl sessions. Participants were allowed a maximum of five attempts to figure out their 1 rep max. During each heavy resistance training session, they completed four sets at around 70-80% of their 1 rep max. The sets had an 8-12 rep max range.

The effect of cross-education

a man in a wheelchair performing a biceps curl
Alesia Kozik / Pexels

Cross-education is a neurophysiological occurrence where researchers witness an increase in strength in an untrained limb after unilateral strength training on the opposite side. Changes at the muscular, spinal, and neural levels result in this cross-transfer. In another example, a basketball player might learn to dribble with his right hand, and then he’s able to successfully dribble with his left hand despite having no previous training on his left side. 

Cross-education or cross-transfer occurs due to changes in the nervous system, not the muscles. The researchers were keen to see the extent of this cross-education effect involving the nervous system. 

The results

close up biceps bicep curl one arm muscles muscular
Tima Miroshnichenko / Pexels

Here are the conclusions:

Strength

  • Non-dominant arm — The D + ND group gained 2.7 kg in strength in the non-dominant arm, and the ND-only group gained similar strength at 2.6 kg. The D-only group gained 1.5 kg in strength, whereas the control group that didn’t do any strength training lost strength in the non-dominant arm.
  • Dominant arm — The D + ND group gained 2.5 kg of strength in the dominant arm, and the D-only group gained 2.3 kg. The ND-only group gained 1.3 kg; once again, the control group lost -0.1 kg of strength.

Hypertrophy

Muscle growth was only seen in the trained arm. The untrained arm didn’t show an increase in muscle size as a result of cross-transfer.

-man doing one arm unilateral bicep curl dumbbel
RDNE / Pexels

Neural Adaptations

While there wasn’t an increase in muscle growth, the researchers did see an increase in muscle strength driven by neural changes and cross-education. They concluded that unilateral or single-arm resistance training boosted strength in the other untrained arm without changing the muscle thickness. This is called the cross-education of strength.

The takeaway

dumbbell outside on floor weights stack rack
Anete Lusina / Pexels

It turns out that doing bicep curls and resistance training on one arm can increase strength in your other arm due to neural changes, but it likely won’t increase the muscular size of the untrained arm. Not doing any resistance training at all could cause a loss in muscle strength. Researchers continue to explore the fascinating concept of cross-education. For now, it’s just another reason to continue putting in the effort and curling those weights.

Topics
Steph Green
Steph Green is a content writer specializing in healthcare, wellness, and nutrition. With over ten years of experience, she…
Can soaking in a hot tub and running yield similar benefits? Surprising UK study
Here are more reasons to sink into that Jacuzzi and relax
man hot tub relax indoors

If you enjoy sinking into a hot tub, you know that familiar feeling when the jets massage your back, and the hot water soothes your muscles and mind. Whether you use the Jacuzzi at your local gym or on vacation or you’re a hot tub owner, mounting research highlights the benefits of hot water immersion and using hot tubs. For example, a study showed that the massaging hot tub jets along with the hot water soothes tense muscles and promotes relaxation. Another study showed that soaking in a hot tub promotes more peaceful sleep and increases levels of hormones like serotonin that help you drift off to sleep.

It’s widely known that exercise and running also provide a range of health benefits, but it requires more effort and energy than simply sitting in a tub. Recently, researchers wanted to understand if sitting in a hot tub and going for a run have similar benefits, and you might be surprised by the results. Let’s look at the study.
The study

Read more
New study explores whether regular exercise can lower your risk of dementia
Does prioritizing your fitness help protect your brain health?
man exercising running around outdoors dark grey sky

We all want to protect our brains and bodies from disease and decline and stay sharp and vibrant throughout the decades. Regular exercise is part of a healthy lifestyle, and it brings a range of benefits, from lowering blood pressure to perking up your mood and prompting the release of feel-good endorphins. Your training habits can benefit your physical health and your brain health, too. For example, an interesting study showed that people who took part in aerobic fitness training had increased brain volume and white and gray matter. 

Physical activity can sharpen problem-solving, memory, and learning and reduce depression or anxiety. Another study concluded that cognitive decline is nearly twice as common in adults who are inactive compared to active adults. In a recent study, researchers wanted to look at how exercise lowered the risk of dementia. Let’s take a look at the study and the results.
The study

Read more
Does working out too close to bedtime affect your sleep quality? Study finds out
Could there be a negative side to exercising later in the evening?
kettlebell at sunset next to fence workout

Sometimes, later in the evening seems to be the only or the best time to work out. Maybe the daytime tangled you up with responsibilities, and now it’s dark outside, and instead of putting on your pajamas, you’re lacing up your sneakers. As the old adage goes, ‘Any exercise is better than no exercise,’ and getting your muscles moving provides numerous health benefits, from lowering your blood pressure to boosting your mood and cardiovascular fitness. 

However, some question whether working out too close to bedtime negatively affects sleep quality. Could there be a downside to getting your fitness in and those endorphins flowing later in the day? Researchers set out to explore these questions in a recent study. 
The study

Read more