If you were to think of the most popular upper body exercise (or even the most popular exercise itself), there’s a good chance the bench press comes up.
Generally, when talking or thinking about the bench press, most people probably think of the barbell bench press.
However, there are a few other modalities you can perform the bench press with.
In a previous article, we assessed how the smith machine bench press compared to the barbell bench press.
In this article, based on the research, we’ll be comparing the dumbbell bench press to the barbell bench press for muscle mass (hypertrophy).
Before detailing the research, it’s important to mention what style of dumbbell bench press we’re discussing.
There are different ways you can execute a dumbbell bench press, but the most common one is where you begin with the dumbbells together and then move them away from each other on the lowering phase.
In all of the research we’ll be assessing, this seems to have been the dumbbell bench press style used. Therefore, much of the information detailed in this article is specific to this dumbbell bench press style and may not necessarily apply to others.
Although, near the end of the article, I’ll mention and discuss some other dumbbell bench press styles.
Table of Contents
Stability Differences
When comparing how a barbell bench press feels to a dumbbell bench press, one of the most apparent differences is stability.
Both of your hands comfortably hold on to the barbell (a single object). Moreover, there are only so many ways you can move the barbell due to its structure.
Contrastingly, each of your hands independently holds on to a dumbbell, creating more freedom of movement. You can move the two dumbbells asymmetrically (your left hand does a movement with a dumbbell that is different from the movement performed with the dumbbell in the right hand).
Does any of this matter for hypertrophy outcomes?
There are some that believe that greater stabilization requirements are more beneficial. It’s hypothesized that greater instability necessities greater muscle activation, resulting in a more powerful stimulus for muscle mass.
However, there are also opposing thoughts to this notion. Some believe that excessive instability may hinder one’s ability to truly produce muscle force, thereby actually preventing an optimal stimulus for muscle hypertrophy.
We’ll explore these ideas more in the muscle activation and hypertrophy outcomes section of this article.
Which Are You Stronger On?
Unsurprisingly, it seems people are generally stronger on the barbell bench press.
A study by Saeterbakken et al. found that in individuals with an average of 4.6 years of training experience, one-rep max on the barbell bench press was statistically significantly greater than one-rep max on the dumbbell bench press.
Unfortunately, they did not provide the exact values, only a graph that is pretty hard to decipher.
When assessing the number of repetitions an individual can perform between a dumbbell and barbell bench press with a given load, it’s also unsurprising to find that performance is superior with the barbell variation.
Heinecke et al. had college football players perform repetitions to failure on the dumbbell and barbell bench press with a 91g load (so with the dumbells, each dumbbell was 45.5kg).
On average, subjects performed 13.8 repetitions with the barbell, but only 12.5 with the pair of dumbbells.
Of course, this isn’t a massive difference, but it is a difference nonetheless.
The discussed differences in stabilization are likely one of the reasons why you can perform better on the barbell bench press.
However, there is also another (less talked about) reason that may play a role here, relating to the triceps. We’ll touch on this in the (next) muscle activation section.
Muscle Activation
In addition to the discussion on if stabilization differences could impact muscle activation, I have come across arguments suggesting that the motions used during a dumbbell bench press may be conducive towards greater chest activation.
Dumbbell bench presses may involve more horizontal flexion (bringing your arms towards the midline of your body), a primary function of the chest.
With the dumbbell bench press style we’re discussing, after the lowering phase, you press and bring the dumbbells together (more horizontal flexion, as your arms get closer towards the midline of your body).
Contrastingly, with a barbell bench press, given your hands do not move on the barbell during the execution of the movement, the arms stay at more or less the same distance away from the midline of the body.
Indeed, there one study by Farias et al. finding that the dumbbell bench press elicited greater chest activation compared to the barbell bench press.
As a note, activation was measured (and averaged) from the middle repetitions of 4 sets with a 10 rep-max load.
However, there are two other studies that do not support this.
Saeterbakken et al. found that during a one-rep max on both exercises, there was similar activation of the chest between the dumbbell and barbell bench press.
Similarly, Welsch et al. found that during the first 3 reps with a 6 rep-max load, activation of the chest was similar between the dumbbell and barbell bench press.
So, although it’s far from overwhelming, the slight majority of evidence suggests that the dumbbell and barbell bench press induce similar chest activation.
Why might this be?
Although the dumbbell bench press may involve more horizontal flexion, it may just be insignificant for chest activation.
Aside from the chest, the anterior deltoid and triceps are the two other muscles that are heavily involved in the bench press.
How does activation of these muscles compare between the dumbbell and barbell bench press?
The studies by Saaterbakken et al. and Welsch et al. explored anterior deltoid activation. They both found the dumbbell and barbell bench press elicited similar activation of this muscle.
As for the triceps, Saeterbakken et al. and Farias et al. both found that dumbbell bench pressing produced less activation of this muscle group compared to barbell bench pressing.
This finding makes sense.
The barbell bench press involves lateral forces, something the triceps heavily contribute towards.
Let me explain this further.
Most people typically only think of vertical forces with the bench press. That is the force generated to lift the bar (or dumbbell) up.
However, with a barbell bench press, individuals actually also generate lateral forces.
Lateral forces are forces directed away from the center of the body.
Think of lateral forces as trying to tear the barbell apart with both of your hands during a barbell bench press. Your left hand is applying force left, while your right hand is applying force right.
In a barbell bench press, lateral forces are around 25% of the vertical forces.
As mentioned, the triceps play a heavy role in producing this lateral force.
With a dumbbell bench press, it’s more or less impossible to apply meaningful lateral forces (you can’t tear the two dumbbells away from each other). If you tried, you’d throw the dumbbells on either side of you to the floor.
The fact you cannot apply meaningful lateral forces to the dumbbell bench press may further explain why individuals are weaker on this exercise compared to a barbell bench press.
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Hypertrophy Outcomes
Despite there being some differences between the dumbbell and barbell bench press, there are many similarities.
For one, both movements more or less involve similar motions at the shoulder and elbow joints, and both are typically executed with a similar range of motion.
Moreover, as just established, both likely similarly recruit the chest and anterior deltoid muscles.
Consequently, I think it’s highly likely the dumbbell and barbell bench press would similarly grow the chest and anterior deltoid.
For the triceps, though, the barbell bench press is most likely superior, thanks to the presence of lateral forces (and hence greater triceps activation).
Some may be thinking of the stability differences and if this can impact hypertrophy.
All in all, differences in stability do not seem to be immensely important for muscle mass outcomes.
A study by Schwanbeck et al. compared a machine-only program to a free weight-only (barbells and dumbbells) program.
Of course, machines provide the most stable environment while free weights the most unstable.
Muscle hypertrophy outcomes were similar between both groups, indicating stability differences do not play a significant role in building muscle.
As a result, the fact dumbbell bench presses are more unstable than barbell bench presses is likely neither advantageous nor disadvantageous for building muscle mass.
Other Dumbbell Bench Press Variations
As promised near the start of the article, I thought it’d also be useful to discuss other dumbbell bench press variations.
The most common style was probably the one discussed in this article, where you begin with the dumbbells together and then move them away from each other on the lowering phase.
Neutral Grip
Another somewhat popular way is performing the dumbbell bench press is with a neutral grip, depicted in the image below:
It is possible that the change in hand position could somehow alter muscle activation patterns, but I’m unaware of any research that would be insightful here.
Additionally, there is less horizontal flexion movement in this style, but whether this could impact chest involvement isn’t clear.
Aside from these potential points, I can’t really think of any solid reason as to why this execution would result in less chest and anterior deltoid activation.
However, I think it is plausible that this dumbbell style could elicit greater triceps activation than the dumbbell style we’ve been discussing throughout this article.
Firstly, performing the dumbbell bench press with a neutral grip typically results in more range of motion at the elbow joint specifically. The greater range of motion of resisted elbow extension could enhance triceps involvement.
Secondly, another byproduct of more range of motion at the elbow is that at the bottom of the movement (when the dumbbells are at or below chest levels), the triceps are more stretched than they would be in the other dumbbell style we’ve been discussing.
Greater stretch under load seems to be quite a powerful stimulus for muscle growth.
Anecdotally, I think many people also feel more triceps activation during this dumbbell style.
Nonetheless, hopefully future research can substantiate these claims.
Unilateral Dumbbell Bench Press
Performing dumbbell bench presses with one arm at a time is also somewhat popular.
Training with dumbbells itself is likely a good way to reduce any imbalances between either side of your body.
However, training unilaterally (one side at a time) can be quite insightful for truly revealing any strength differences you may have between the two sides of your body.
For some people, these differences can be notable.
For instance, Heinecke et al. found that, on average, a group of college football linemen performed 18 reps to failure with their right hand with a 45.5kg dumbbell and only 15.4 reps to failure with their left hand.
Therefore, training with a unilateral dumbbell bench press can be useful for assessing any imbalances.
In total, as far as hypertrophy for the main muscle groups, I don’t think there’s any solid evidence to suggest that the unilateral dumbbell bench press could be superior or inferior to bilateral (two-arm) bench presses.
However, the unilateral dumbbell bench press may be more favorable for strengthening/developing the abdominal and oblique muscles.
The asymmetrical loading in this exercise likely requires greater stabilization from the core muscles.
Indeed, research has demonstrated that unilateral exercises can place more stress on the abdominal and oblique muscles compared to bilateral exercises.
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