If you're grinding in the gym to build a stronger, more muscular chest, you've probably done the barbell bench press (BBP) and dumbbell flyes (DF). These are go-to exercises for upper-body strength, but have you ever wondered which one fires up your muscles more? A 2020 study in the Journal of Sports Science & Medicine tackles this question, comparing muscle activation in the BBP and DF among resistance-trained men. Let's break it down in a clear, easy-to-read way, explain key technical terms, and figure out what it means for your next chest day. Spoiler: both exercises have their place, but one might be the champ for most lifters.
What's the Study All About?
The study, "A Comparison of Muscle Activation between Barbell Bench Press and Dumbbell Flyes in Resistance-Trained Males," involved 17 men (average age 22.9 years, with about 4.8 years of lifting experience). These guys were gym veterans, making them perfect for testing consistent exercise form. The researchers compared muscle activity in four key muscles during the BBP and DF:
- Pectoralis Major: The main chest muscle that drives pushing movements.
- Anterior Deltoid: The front part of your shoulder muscle, helping with shoulder flexion.
- Triceps Brachii: The muscle on the back of your upper arm, key for elbow extension.
- Biceps Brachii: The front arm muscle, often an antagonist (opposing muscle) in pressing moves.
They used surface electromyography (sEMG), a technique that measures electrical activity in muscles, to track muscle excitation during a 6-repetition maximum (6RM) load—the heaviest weight each guy could lift for six reps. For deeper insights, they zoomed in on the fifth rep, splitting it into six phases: the lower, middle, and upper parts of the descending phase (lowering the weight) and ascending phase (pushing or lifting the weight). This showed how muscle activation changed throughout the movement.
The BBP is a multi-joint exercise, involving both shoulder and elbow motion, while the DF is a single-joint exercise, focusing mostly on shoulder movement with minimal elbow action. The study aimed to uncover how these biomechanical differences affect muscle activation.
Key Findings: How Do the Exercises Stack Up?
The results showed clear differences in muscle activation, with each exercise excelling in different areas. Let's dive into the details for each muscle.
Pectoralis Major: Bench Press Rules
The pectoralis major, your chest's heavy hitter, was more active in the BBP:
- 16% higher activation overall compared to the DF (effect size: 0.36, a small difference).
- In the descending phase, the BBP had greater activation in all three phases: upper (42%), middle (21%), and lower (23%).
- In the ascending phase, only the upper phase showed higher activation (34%) in the BBP, with no significant differences in the middle or lower phases.
Why? The BBP lets you lift heavier loads (about 88.5 kg vs. 40.5 kg for DF), which ramps up the demand on the pecs. The BBP's external moment arm (the leverage from the weight) stays fairly constant, keeping the pecs engaged throughout. In contrast, the DF's moment arm changes—longest at the bottom (stretching the pecs) and shortest at the top—potentially reducing pec activation in some phases.
Anterior Deltoid: Bench Press Wins Again
The anterior deltoid also worked harder in the BBP:
- 25% higher activation overall (effect size: 0.84, a medium-to-large difference).
- In the ascending phase, the middle (14%) and upper (46%) phases had greater activation in the BBP.
- In the descending phase, only the middle phase (30%) showed higher activation in the BBP.
The heavier loads and multi-joint nature of the BBP likely drive this. The anterior deltoid stabilizes and flexes the shoulder, and the BBP's steady moment arm keeps it active. The DF, with its shifting moment arm, demands less from the deltoid in certain phases.
Triceps Brachii: Bench Press Dominates
The triceps brachii was a slam dunk for the BBP:
- 75% higher activation overall (effect size: 1.47, a large difference).
- Greater activation in all phases of both the descending (62–72%) and ascending (75–84%) parts.
This is no surprise. The BBP involves elbow extension, where the triceps thrive, as you push the barbell up. In the DF, the elbow stays mostly fixed at a slight bend (150–160°), so the triceps act as stabilizers, not prime movers, leading to much lower activation.
Biceps Brachii: Flyes Steal the Show
The biceps brachii, usually an antagonist in these exercises, was the standout for the DF:
- 76% higher activation overall (effect size: 3.07, a very large difference).
- Greater activation in all phases of both the descending (57–71%) and ascending (69–86%) parts.
This was unexpected, as biceps aren't the focus of chest exercises. In the DF, the biceps likely work harder to stabilize the elbow joint, especially with independent dumbbells, which are less stable than a barbell. The biceps may also assist in shoulder adduction (pulling the arms toward the body), particularly when the elbow is extended in the DF. In the BBP, the biceps act more as an antagonist, resisting elbow extension, which keeps their activation lower.
Extra Notes: Load and Timing
Participants lifted much heavier loads in the BBP (88.5 kg) than in the DF (40.5 kg), which likely boosted activation of the pecs, deltoids, and triceps. The DF took longer to complete (23.5 seconds vs. 18.7 seconds for BBP), possibly due to the extra control needed with dumbbells.
What Does This Mean for Your Workouts?
How can you use this to supercharge your chest training? Here are some practical tips:
Choose Barbell Bench Press for Max Muscle Activation
If you want to maximize strength and growth in your chest, shoulders, and triceps, the BBP is your best bet. Its higher activation and heavier loads make it a staple for most lifters.
Use Dumbbell Flyes for Specific Needs
The DF excels for biceps activation and can help with exercises requiring horizontal shoulder flexion with extended elbows, like throwing or pressing motions in sports. It's also great for isolating the pecs and boosting shoulder stability, especially in rehab or specialized programs.
Mix Both for Variety
While the BBP is more effective overall, adding DF brings variety, hits the biceps unexpectedly, and challenges stability. A smart program might focus on BBP (e.g., 70% of your chest volume) with DF as a complementary move.
Target Weak Points with Phases
The BBP's consistent activation across the range of motion makes it great for addressing weak spots, like the top of the press. The DF's lower phase stretches the pecs, which could enhance growth through increased mechanical tension (the force stretching the muscle).
Limitations and What's Next
The study isn't flawless. It only included resistance-trained men, so results might not apply to beginners, women, or other groups. sEMG can pick up cross-talk (signals from nearby muscles), and dynamic movements can muddy the data. Also, it focused on immediate activation, not long-term muscle or strength gains.
Future research could test these exercises in different populations, try other equipment (e.g., cables or machines), or track muscle growth over time. Exploring how grip width in the BBP or elbow angle in the DF affects activation would be cool too.
Reference
This article is based on the research study: "A Comparison of Muscle Activation between Barbell Bench Press and Dumbbell Flyes in Resistance-Trained Males" published in the Journal of Sports Science & Medicine (2020). You can access the original study here: https://pmc.ncbi.nlm.nih.gov/articles/PMC7675616/
Final Thoughts
The barbell bench press comes out on top for activating the pectoralis major, anterior deltoid, and triceps brachii, making it a must for most strength and hypertrophy programs. But don't dismiss dumbbell flyes—they boost biceps activation and offer unique benefits for stability and specific movements. By strategically using both, you can build a stronger, more balanced upper body.
Next chest day, try kicking off with heavy BBP sets to maximize load and activation, then add some DF to stretch the pecs and work your stabilizers. You'll have the science to back your gains. Happy lifting!