Different incline bench press angles can work your muscles in different ratios and offer other benefits. Find out whether 15 or 30 degrees is better.
15-degree bench presses will generally be better than the 30-degree version for working the lower and middle pectoral (chest) muscles.
On the flip side, the 30-degree bench press will generally work your upper chest and deltoid muscles slightly more than the 15-degree version.
Both exercises work all of these parts to some extent but these different ratios will apply. This is not necessarily better or worse for everyone. Your training goals matter.
Besides these things, you want to keep in mind that comfort and enjoyment matter too. You may prefer one of the two angles.
Additionally, switching up between 15 degrees, 30 degrees, other degrees of bench press angles, or incline bench press alternatives can also help you avoid plateaus.
Ratio muscles worked
While many people are aware of it, it is worth mentioning that the standard different incline bench press angles will generally all work the pectoral muscles, triceps, and deltoids.
However, by switching up the angles with a good FID bench, you change in what ratio your muscles have to work.
This is because muscles and different parts of these muscles contract to pull the bones they are attached to closer to each other.
By changing the angle of your bench press, your bones have to be pulled in a slightly different direction.
With these principles, you can already estimate to some extent what the difference is between 15 and 30 degree bench presses in terms of muscles worked.
More specifically, with the laws of physics and biology, it would seem that 30-degree bench presses will work the upper chest and front deltoids more than the 15-degree bench press.
In turn, the 15-degree bench press will work the middle and lower parts of the pectoral muscles more than the 30-degree bench press.
In some exercises like tricep dips you definitely want some studies that look at the ratio of muscle engagement more in-depth.
For the bench press, studies like this may not be as necessary but interesting to see anyways.
One study with 30 trained adults measured the EMG activity in different muscles during 0, 15, 30, 45, and 60 degree bench presses.
They measured that the 15-degree bench press had more middle and lower chest muscle engagement than the 30-degree bench press (1).
Additionally, the 30-degree bench press had the highest upper-chest muscle engagement of all the options although this was not statistically significantly different from the 15-degree bench press.
Similarly, the EMG activity values of the anterior (front) deltoids were slightly higher in the 30-degree bench press than in the 15-degree version but not statistically significantly different.
The triceps brachii engagement was similar in all bench press angles.
You can be skeptical about the differences that are not statistically significant but in combination with the principles from the previous section, it is likely that more data would make the numbers statistically significant.
Most people will be interested in how 15-degree bench presses and the 30-degree version compare in terms of what ratio they work your muscles.
However, other training details like how comfortable you find each angle matter too.
Anecdotally, some people find 30-degree angle bench presses more comfortable on their shoulder joints.
That being said, this difference is still somewhat subjective and dependent on your personal body.
If comfort matters to you, you likely want to give both incline bench press angles a try to feel how they compare.
While comfort is part of this, you may also simply prefer either 15 or 30-degree bench presses for more unexplainable reasons.
Unless you have great self-discipline, part of a good workout program is enjoying the exercises you do at least somewhat. This is not just something nice to have. It could also help improve consistency.
So if you prefer one of the two angles more and don’t care too much about the other differences, this detail can help you make your decision.
Benefits of changing things up
Lastly, something to note is that simply changing up training details like the angles you choose for your bench presses can offer other benefits too.
If you continue the exact same workout program with the same exercises, repetitions, weights, etc., you will hit a muscle growth and strength progress plateau sooner or later.
At this point, changing up your workout routine by switching between 15 or 30 degree bench presses (or changing other details like what exercises you do or bench press equipment you use) can help you see more results.
Additionally, you may also like the way changing up your incline bench press angles adds some variety to your workout program.