For many years, the Parallel Bar Dip has been considered a key exercise for pectoral development. Many of us have seen photos of Arnold doing parallel bar dips, with additional weight hanging from his waist. Fitness / bodybuilding magazines routinely print articles touting Parallel Bar Dips at part of a “good” chest routine.
However, many people would be surprised - maybe even upset - at the notion that perhaps Dips are not a very good pectoral exercise. Let’s take a good, hard look at this exercise - as well as the anatomy of the pectoral muscles - and evaluate how good it is or isn’t, for pectoral development (i.e., bodybuilding / muscular hypertrophy).
Let’s start by first establishing what constitutes a “good exercise” - for any body part. There are specific mechanical principles that must be in place - ideally - in order for an exercise to be considered “good”.
Consider the Standing Barbell Curl. It’s a good exercise, and there are mechanical reasons why this is so. The biceps muscle originates high on the humerus (upper arm bone) - actually just above it, on the scapula (shoulder blade). The biceps fibers run down the length of the upper arm, cross the elbow joint, and insert on the upper portion of the forearm bones. When we perform a Standing Barbell Curl, we bend and straighten the arm - that much is obvious. But there are two things that may not be so obvious.
The forearm is traveling through a particular pathway, and that pathway runs parallel to the target muscle’s (biceps) fibers. This is one of the criteria for a “good” exercise - that the lever being operated by the target muscle, travel the correct pathway - which is usually parallel to its fibers.
Also, as the elbow straightens, the insertion of the biceps (again, located at the upper part of the forearm bones) moves farther away from the origin the biceps (located high on the upper arm bone / scapula). How else would the biceps stretch (i.e., elongate)? This is critically important. Dynamic exercise (resistance exercise that involves movement / range of motion) requires that a muscle be contracted and elongated, against resistance. The first half of this equation requires that the insertion of the muscle, move away from the origin of the muscle - thereby causing muscle elongation.
The second half of that equation is the contraction - in the case of the Standing Barbell Curl - bending the elbow fully. This causes the insertion of the biceps to move directly toward the origin of the muscle. “Full range of motion” dictates that the muscle fully elongate, and then fully contract (shorten).
In the illustration below, we see the muscle fibers of the pectorals. As you can see, most of the fibers originate on the sternum. Roughly 75% of the fibers originate there. Another smaller percentage originate on the ribs, and another percentage originate on the clavicle (collar bone).
Since the majority of the pectoral muscle fibers run from the sternum out (laterally) to (the upper part of) the upper arm bone, it makes sense that the movement of the upper arm bone, during a chest exercise, be parallel to those fibers.
The only way to stretch the pectoral fibers, is to cause the insertion of the pectoral muscle to move away from the origin of the fibers (located on the sternum). This requires that we move the arm laterally - straight out to the side of the torso - away from the sternum.
Conversely, the contraction of the pectoral muscles would require the insertion of the pectoral muscles (on the upper arm bone) to move maximally toward the origin of the fibers (located on the sternum).
This is precisely what occurs when performing a Flat (prone) Dumbbell Press. The upper arm swings out, away from the sternum - and then back toward the sternum. Ideally - the goal is maximum range of motion. So the wider the distance between the origin and the insertion (in the stretch position) - the better. Likewise, the closer the distance between the origin and the insertion (in the contraction) - the better. The Flat Dumbbell Press is - therefore - a good chest exercise for pectoral development.
But that is not what happens during a Parallel Bar Dip. Instead of having the upper arm bone move laterally - to the side of the torso - it moves more in a backward direction. This is due to the fact that the bars are stationary. They don’t move laterally - the way dumbbells move with us, out to the sides. This forces are elbows to go back (posteriorly), instead of out (laterally). So, even though we might be in the lowest (stretch) position, our pectoral insertion has not moved as much laterally (to the side) as it would have on a Dumbbell Press, a Butterfly Machine, a Cable Crossover, or even a Bench Press. All of those exercises cause the upper arm bone to move outward - laterally (to the sides) - away from the sternum and the origin of the pectoral fibers.
In the contraction phase of the Parallel Bar Dip, it's also less-than-ideal. The best contraction of the pectoral muscle, occurs when we maximally shorten (flex) it. This is achieved when we bring the upper arms forward, in front of our body, and toward the center. This causes the muscle insertions (high on the upper arms) to move maximally toward the muscle origin (on the sternum).
But since the dip bars are stationary, they prevent us from being able to bring the hands close together. So instead of contracting our pecs with our hands in front of our body, where maximum pectoral contraction occurs, we end up with our hands alongside our body (somewhere near our hips...not in front of our body), and about 18 inches away from a full pectoral contraction.
If we could somehow angle our bodies during a Parallel Bar Dip, such that our feet were farther back, thereby putting our torso in a slightly more perpendicular position with gravity - we'd be able to push slightly more forward (in front of our body), rather than downward - and this would be good. And if we could cause the bars to widen as we sink into the dip, and then come together as we rise up and enter the contraction, it would be even better. But we can't do that.
Interestingly, you’ll notice that - during a parallel bar dip - the upper arm bones travel along a pathway that is more parallel to the muscle fibers of the anterior deltoids. And - sure enough - Dips hit the anterior deltoids MORE than they hit the pectorals, precisely for that reason.
Certainly, an argument could be made that Parallel Bar Dips work the pectoral fibers that originate on the ribs. They comprise about 15% of the total pectoral fibers, and they do add a beautiful outer/lower sweep to the pecs. So, there is a justification for doing an exercise that stimulates THOSE muscle fibers. However, dips are not the best exercise for those fibers.
Any decline movement - whether with dumbbells or cables, or even a barbell - would be more productive - even for the lower fibers that originate on the ribs, because it would allow the arms to move outward (away from the sternum), and because they provide resistance from behind the torso, rather than from below the torso.
A Better Alternative
A great substitute for the Parallel Bar Dips is the Decline Cable Press, on a Free Motion machine (pulleys closer to each other than a typical Cable Crossover). This would be like a Parallel Bar Dip, in the sense that you’re relatively upright - although sightly more bent over - and this bent over position allows you to face more in the opposite direction from the resistance (which is good). The freedom of the cables allows you to bring the arm outward - laterally - thereby causing the pectoral insertion (on the upper arm bones) to move away from the sternum (the origin of the pectoral fibers). Then, you can bring the hands all the way together in front, which causes the pectoral insertions to move maximally toward the pectoral origins.
This cable movement runs parallel to the pectoral fibers (...as it should), provides better pectoral stretch than Dips, and provides better pectoral contraction the dips. Plus, you can dial in the exact weight that feels right. You're not obligate to use your entire bodyweight.