If you're working hard 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 works your muscles more? A 2020 study in the Journal of Sports Science & Medicine tackles this question, comparing muscle activity in the BBP and DF among trained men. Let's break it down in a clear, easy-to-read way, explain key terms, and figure out what it means for your next chest day. Spoiler: both exercises have their place, but one might be the winner for most lifters.
What's the Study All About?
The study, "A Comparison of Muscle Activity between Barbell Bench Press and Dumbbell Flyes in 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:
- Main Chest Muscle: The main chest muscle that drives pushing movements.
- Front Shoulder: The front part of your shoulder muscle, helping with shoulder movement.
- Triceps: The muscle on the back of your upper arm, key for straightening your elbow.
- Biceps: The front arm muscle, often working against other muscles in pressing moves.
They used special equipment that measures electrical activity in muscles to track muscle work during a 6-repetition maximum (6RM) load—the heaviest weight each guy could lift for six reps. For deeper insights, they looked closely at the fifth rep, splitting it into six parts: the lower, middle, and upper parts of the lowering phase (lowering the weight) and lifting phase (pushing or lifting the weight). This showed how muscle activity 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 little elbow action. The study aimed to uncover how these differences affect muscle activity.
Key Findings: How Do the Exercises Compare?
The results showed clear differences in muscle activity, with each exercise being better in different areas. Let's dive into the details for each muscle.
Main Chest Muscle: Bench Press Rules
The main chest muscle, your chest's heavy hitter, was more active in the BBP:
- 16% higher activity overall compared to the DF (a small but meaningful difference).
- In the lowering phase, the BBP had greater activity in all three parts: upper (42%), middle (21%), and lower (23%).
- In the lifting phase, only the upper part showed higher activity (34%) in the BBP, with no big differences in the middle or lower parts.
Why? The BBP lets you lift heavier loads (about 88.5 kg vs. 40.5 kg for DF), which increases the demand on the chest muscles. The BBP's leverage from the weight stays fairly constant, keeping the chest muscles working throughout. In contrast, the DF's leverage changes—longest at the bottom (stretching the chest) and shortest at the top—possibly reducing chest muscle activity in some parts.
Front Shoulder: Bench Press Wins Again
The front shoulder also worked harder in the BBP:
- 25% higher activity overall (a medium-to-large difference).
- In the lifting phase, the middle (14%) and upper (46%) parts had greater activity in the BBP.
- In the lowering phase, only the middle part (30%) showed higher activity in the BBP.
The heavier loads and multi-joint nature of the BBP likely drive this. The front shoulder helps stabilize and move the shoulder, and the BBP's steady leverage keeps it active. The DF, with its changing leverage, demands less from the shoulder in certain parts.
Triceps: Bench Press Dominates
The triceps was a slam dunk for the BBP:
- 75% higher activity overall (a large difference).
- Greater activity in all parts of both the lowering (62–72%) and lifting (75–84%) phases.
This is no surprise. The BBP involves straightening your elbow, 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 main movers, leading to much lower activity.
Biceps: Flyes Steal the Show
The biceps, usually working against other muscles in these exercises, was the standout for the DF:
- 76% higher activity overall (a very large difference).
- Greater activity in all parts of both the lowering (57–71%) and lifting (69–86%) phases.
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 help in pulling the arms toward the body, particularly when the elbow is extended in the DF. In the BBP, the biceps act more against other muscles, resisting elbow extension, which keeps their activity lower.
Extra Notes: Weight and Timing
Participants lifted much heavier weights in the BBP (88.5 kg) than in the DF (40.5 kg), which likely boosted activity of the chest, shoulders, 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 improve your chest training? Here are some practical tips:
Choose Barbell Bench Press for Max Muscle Activity
If you want to get the most strength and growth in your chest, shoulders, and triceps, the BBP is your best bet. Its higher activity and heavier weights make it a staple for most lifters.
Use Dumbbell Flyes for Specific Needs
The DF is great for biceps activity and can help with exercises requiring horizontal shoulder movement with extended elbows, like throwing or pressing motions in sports. It's also great for isolating the chest muscles and boosting shoulder stability, especially in rehab or special 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 supporting move.
Target Weak Points with Phases
The BBP's consistent activity 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 chest muscles, which could help growth through increased stretching force.
Study Limitations and What's Next
The study isn't perfect. It only included trained men, so results might not apply to beginners, women, or other groups. The equipment can pick up signals from nearby muscles, and moving exercises can make the data unclear. Also, it focused on immediate activity, 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. Looking into how grip width in the BBP or elbow angle in the DF affects activity would be interesting too.
Reference
This article is based on the research study: "A Comparison of Muscle Activity between Barbell Bench Press and Dumbbell Flyes in 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 working the main chest muscle, front shoulder, and triceps, making it a must for most strength and muscle-building programs. But don't dismiss dumbbell flyes—they boost biceps activity and offer unique benefits for stability and specific movements. By smartly using both, you can build a stronger, more balanced upper body.
Next chest day, try starting with heavy BBP sets to get the most weight and activity, then add some DF to stretch the chest muscles and work your stabilizers. You'll have the science to back your gains. Happy lifting!