If you've ever hit the gym to pump up your biceps, you've probably done a biceps curl or two. It's a classic exercise for building those eye-catching arm muscles. But did you know that the way you grip the bar or dumbbell can change which muscles are working and how hard? A fascinating new study published in the journal Sports dives into this very question, exploring how different handgrips—supinated, pronated, and neutral—affect the activation of the biceps brachii, brachioradialis, and anterior deltoid during the biceps curl.
What's the Study About?
The study, titled "Biceps Brachii and Brachioradialis Excitation in Biceps Curl Exercise: Different Handgrips, Different Synergy," was conducted on ten competitive bodybuilders. These folks know their way around a gym, making them ideal for a study requiring consistent exercise technique. The researchers wanted to see how three different handgrips affect muscle excitation (how much a muscle is activated) during the biceps curl.
The grips they tested were:
- Supinated Grip (palms facing up, like you're holding a bowl of soup)
- Pronated Grip (palms facing down, as if you're pushing something away)
- Neutral Grip (palms facing each other, like holding a hammer)
They used surface electromyography (sEMG), a technique that measures electrical activity in muscles, to track the excitation of three muscles:
- The biceps brachii (the big muscle on the front of your upper arm)
- The brachioradialis (a forearm muscle that helps flex the elbow)
- The anterior deltoid (the front part of your shoulder muscle)
The biceps curl was performed with a cable machine, using an 8-repetition maximum (8-RM) load, meaning the weight was heavy enough that the participants could only do eight reps before failing.
The study looked at two phases of the curl:
- The ascending phase (lifting the weight up)
- The descending phase (lowering the weight back down)
By analyzing these separately, the researchers could see if the grip affected muscles differently during each part of the movement.
Key Findings: What Happens with Each Grip?
Here's where things get interesting. The study found that the grip you use changes how much each muscle works, and the differences are most noticeable during the ascending phase.
Biceps Brachii: Loves the Supinated Grip
The biceps brachii was the star of the show when using a supinated grip. During the ascending phase, it showed:
- 19% greater excitation compared to the pronated grip (effect size: 2.60, meaning a very large difference)
- 12% greater excitation compared to the neutral grip (effect size: 1.24, a large difference)
In simpler terms, when your palms are up, your biceps work harder. The neutral grip was better than the pronated grip, but not as effective as the supinated one. Interestingly, during the descending phase, there were no significant differences between grips—the biceps activation was similar across all three.
Why does this happen? The biceps brachii isn't just an elbow flexor; it's also a supinator (a muscle that rotates the forearm to turn the palm up). So, when you use a supinated grip, the biceps are in their happy place, doing both jobs at once. A pronated grip, on the other hand, puts the biceps in a less favorable position, reducing their activation.
Brachioradialis: Surprising Results
The brachioradialis, a key forearm muscle, also preferred the supinated grip during the ascending phase:
- 5% greater excitation compared to the pronated grip (effect size: 1.01, moderate difference)
- 6% greater excitation compared to the neutral grip (effect size: 1.10, moderate difference)
This was a bit of a surprise. Many gym-goers believe a neutral grip (like in a hammer curl) maximizes brachioradialis activation because it keeps the forearm in a neutral position, which is this muscle's specialty. But the study suggests that the supinated grip might stretch the brachioradialis more, leading to higher activation. Like the biceps, the brachioradialis showed no significant differences between grips during the descending phase.
Anterior Deltoid: The Stabilizer Steps Up
The anterior deltoid, which stabilizes the shoulder joint during the curl, told a different story:
- During the ascending phase, it was 6% more active with the pronated grip and 9% more active with the neutral grip compared to the supinated grip (effect sizes: 2.07 and 3.18, respectively—very large differences)
- During the descending phase, the pronated grip still showed 5% greater excitation than the supinated grip (effect size: 1.02, moderate difference)
This makes sense when you think about the biceps' role. The biceps brachii, especially its long head, helps stabilize the shoulder when supinated. With a pronated or neutral grip, the biceps are less effective at this, so the anterior deltoid has to work harder to keep the shoulder stable. This is a great example of muscle synergy (how muscles work together to perform a movement).
Ascending vs. Descending: Why the Difference?
Across all grips and muscles, the ascending phase showed higher excitation than the descending phase. This is because the ascending phase involves concentric contraction (muscles shortening to lift the weight), which requires more effort than the eccentric contraction (muscles lengthening to lower the weight) in the descending phase. Eccentric contractions are stronger, so the muscles don't need to fire as intensely to control the weight going down.
Why Does This Matter for Your Workouts?
So, what can you take away from this study for your next gym session? Here are some practical tips:
Want Bigger Biceps? Go Supinated
If your goal is to maximize biceps brachii activation, stick with a supinated grip. It's the most effective for targeting this muscle, especially during the lifting phase.
Mix It Up for Balanced Development
While the supinated grip is great for biceps, the pronated and neutral grips activate the brachioradialis and anterior deltoid more. Including all three grips in your routine can ensure you're hitting your arm and shoulder muscles from different angles, promoting balanced growth and strength.
Consider Phase-Specific Training
The study highlights that the ascending and descending phases have different effects. If you're advanced, you could experiment with emphasizing one phase (e.g., slow eccentrics for more time under tension) to vary the stimulus on your muscles.
Vary Your Grips for Neural and Mechanical Benefits
Changing grips doesn't just target different muscles; it also provides varied neural stimuli (how your brain recruits muscles) and mechanical stress (the physical load on your muscles). This can help prevent plateaus and keep your training fresh.
Limitations and What's Next
The study isn't perfect. It didn't measure other muscles like the brachialis (a deep elbow flexor) or wrist muscles, which could play a role in grip differences. It also focused on competitive bodybuilders, so the results might not apply to beginners or casual lifters. Plus, the study used a cable machine, and results might differ with dumbbells or barbells.
Future research could explore these other muscles, test different equipment, or look at how grip affects less experienced lifters. It'd also be valuable to see studies on how grip variations impact long-term muscle growth, not just immediate activation.
Reference
This article is based on the research study: "Biceps Brachii and Brachioradialis Excitation in Biceps Curl Exercise: Different Handgrips, Different Synergy" published in the journal Sports (2023). You can access the original study here: https://www.mdpi.com/2075-4663/11/3/64
Final Thoughts
This study is a goldmine for anyone serious about arm training. It shows that something as simple as changing your handgrip can significantly alter how your muscles work during a biceps curl. A supinated grip is your go-to for maxing out biceps and brachioradialis activation, while pronated and neutral grips bring the anterior deltoid into the mix for shoulder stability. By mixing up your grips, you can create a well-rounded arm workout that hits multiple muscles and keeps your training varied.
Next time you're curling, try rotating through all three grips in a single session or across your weekly routine. Your biceps, forearms, and shoulders will thank you—and you might just notice some extra gains. Happy lifting!