Dumbbell Bench Press vs Dumbbell Fly: Which Builds the Biggest Chest Muscles?
Key insights: 60-second read
- Dumbbell bench press and dumbbell fly produce similar chest muscle growth - a 10-week study in recreationally trained men found no significant difference in pectoralis major muscle thickness between the two exercises.
- Both exercises increased muscle size across all measured sites - medial, intermediate, and lateral regions of the pectoralis major all grew similarly in both groups.
- The bench press group lifted heavier loads - the average load was 27 kg for the bench press versus 20 kg for the fly, likely compensating for the shorter moment arm and producing similar torque at the shoulder.
- Exercise selection can be based on personal preference - if you have joint pain or difficulty with heavy loads on the bench press, you can switch to the fly without sacrificing chest development.
- The study was limited to recreationally trained men over 10 weeks - results may differ for women, untrained individuals, athletes, or longer training periods.
If you're trying to build your chest, you may have wondered whether the dumbbell bench press or the dumbbell fly is the better choice. Both exercises target the pectoralis major in a way that encourages full range of motion through the shoulder and chest area, but have different biomechanical requirements. The bench press involves more elbow flexion and heavier loads, while the fly keeps the elbows relatively straight and places more tension on the muscle in the lengthened position.
Recent research compared these two exercises over a 10-week training program in recreationally trained men. The findings might surprise you: both exercises produced similar muscle growth.
Let's break down what the research found and what it means for your training.
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Background: The Biomechanics
Exercise selection is one of the main resistance training variables that can influence muscle growth. Different exercises can produce distinct adaptations, especially when they differ in torque, tension, and muscle length.
The dumbbell bench press (DBP) and dumbbell fly (DFLY) are two exercises with a similar degree of shoulder horizontal adduction, but a different degree of elbow flexion. From a biomechanical standpoint:
- Dumbbell Fly: Greater resistance moment arm at the end of the eccentric action (when the muscle is in a lengthened position).
- Dumbbell Bench Press: Shorter moment arm in the lengthened position and less moment arm variation across the range of motion.
"Contrary to our hypothesis, our findings indicated that both exercises elicited similar development of pectoralis major muscle thickness after a 10-week period."
The Study: Methods and Participants
This was the first study to compare different resistance-training exercises (DBP and DFLY) on hypertrophic adaptations of the pectoralis major in recreationally trained males.
Study Details
- Participants: 26 young, healthy males with an average of 3.3 years of resistance training experience.
- Design: Participants were allocated to either the DBP or DFLY group and trained twice a week for 10 weeks.
- Volume: Weekly set volume was individualised based on participants' previous pectoralis major training volume. Average weekly sets were 14 for DBP and 13 for DFLY.
- Intensity: 8-12 repetitions with approximately 2 reps in reserve, except the final set, which was performed to concentric failure.
- Measurement: Pectoralis major muscle thickness was assessed via ultrasound at medial (30%), intermediate (50%), and lateral (70%) sites.
Both groups trained with a controlled tempo (1 second concentric, 2 seconds eccentric) and were supervised by research staff. Participants were instructed to avoid any additional pectoralis major or anterior deltoid exercises outside the study.
What the Results Show
Muscle Thickness
Both groups increased muscle thickness across all measured sites over the 10-week period. However, there were no significant differences between groups at any site:
| Site | DBP Change | DFLY Change | p-value |
|---|---|---|---|
| Medial | +16.8% | +14.0% | 0.500 |
| Intermediate | +10.0% | +11.8% | 0.864 |
| Lateral | +13.1% | +17.4% | 0.720 |
| Sum of MT | +13.1% | +14.6% | 0.985 |
Volume Load
Both groups increased their volume load throughout the intervention. However, the DBP group accumulated more total volume load than the DFLY group. The average load lifted was significantly higher in the DBP group (27 kg vs 20 kg), likely because the bench press allows for heavier loading due to its shorter moment arm.
Key Finding: Despite the DBP group lifting heavier loads, both exercises produced similar muscle growth. This suggests that the greater load in the bench press may have compensated for the shorter moment arm, producing similar torque at the shoulder joint as the fly.
Practical Applications
The takeaway is simple: coaches and practitioners can select either exercise based on personal preference, comfort, and goals.
Similarly, a painful or recovering shoulder may tolerate the shorter moment arm of the bench press more than the dumbbell fly. Clinically, I find the bench press much kinder to anyone with restricted shoulder mechanics and less likely to generate shoulder pain.
- If you prefer one exercise over the other, you can choose based on what feels best for your body and what keeps you consistent.
- If you want variety, you can rotate between the two exercises or include both in your program - though it's unclear whether combining them provides additional benefits.
- If you're time-poor, either exercise alone is sufficient for pectoralis major development.
"Coaches and practitioners can select DBP or DFLY to develop pectoralis major muscle thickness according to their personal preference, comfort and goals of the resistance training program."
Limitations of the Research
The authors acknowledge several limitations:
- Nutritional intake was not tracked - deviations in energy and protein consumption could have influenced results.
- No non-training control group - this limits the strength of the inferences.
- Biomechanical modelling was not performed - the presumed differences in moment arms and torque were not directly measured.
- Population limited to recreationally trained men - results may not apply to women, untrained individuals, athletes, those in pain, or older adults.
- Only pectoralis major was measured - effects on synergist muscles (triceps, anterior deltoid) were not assessed.
- High dropout rate - may have diminished the effectiveness of randomisation.
This study provides the first direct comparison of dumbbell bench press and dumbbell fly for pectoralis major hypertrophy in recreationally trained men. The finding is clear: both exercises produce similar muscle growth.
This means you don't have to choose one over the other based on a belief that one is superior for building your chest. If you enjoy the fly more, or one specifically aggravates your joints, you can make an informed choice without losing out on muscle-building potential.
As always, consistency and progressive overload matter more than the specific exercise you choose. Find what works for you, and stick with it.
- Grant
Frequently Asked Questions
Is the dumbbell fly as good as the bench press for building chest muscle?
Based on this study, yes. Both exercises produced similar increases in pectoralis major muscle thickness over 10 weeks. However, the study was limited to recreationally trained men, so results may differ for other populations.
Why did the bench press group lift heavier loads but not grow more muscle?
The bench press allows for heavier loading because of its shorter moment arm. The fly, with its longer moment arm in the lengthened position, produces greater torque per unit of load. The two effects appear to balance out, resulting in similar muscle growth.
Should I do both exercises in my program?
The study didn't test whether combining both exercises provides additional benefits. If you enjoy both and have the time, including both is reasonable. If you prefer one, either alone is sufficient for chest development.
One key insight from this research
"Both exercises elicited similar general and regional hypertrophy on pectoralis major muscle thickness in recreationally trained individuals. Coaches and practitioners can select dumbbell bench press or dumbbell fly when targeting pectoralis major muscle development based on personal preference and goals."
Reference
Dell'Avanzia, F. G., Enes, A., Alves-Marques, F., Costa-Rodrigues, J., Bello, G., Seima, G., Nassa, G., Moreira, N. F., Santana, C., Mohan, A. E., Piñero, A., Schoenfeld, B. J., & Souza-Junior, T. P. (2025). Dumbbell bench press and dumbbell fly elicit similar pectoralis major muscle hypertrophy in recreationally-trained individuals. ResearchGate. https://www.researchgate.net/publication/414126435
Need personalised guidance for your training?
If you would like help with any shoulder pain or dysfunction, you can book with Grant either in Port Macquarie or via an online telehealth consultation.
