In comparing Chris Bumstead with Arnold Schwarzenegger, let’s start off with their frames. Arnold was around the same height as Chris when competing. Although Arnold had several advantages that will be discussed, Bumstead’s overall body structure conforms more to what pre Arnold-era bodybuilders were striving for, wide straight shoulders, and narrow hips and waist. Schwarzenegger had more of a sloping shoulder look that wasn’t seen much before his era. The overall structure and look of bodybuilders like Steve Reeves and Jim Haislop were considered more of the ideal but, when Schwarzenegger came along, he had so many new things added to the mix, along with an overall flow of his own, that his body type worked, and became a new standard.
Schwarzenegger had biceps peaks that are hard to compete with. Although Bumstead has some of the shortest biceps insertions in bodybuilding, he’s done a remarkable job bringing his biceps into proportion with the rest of his physique. Comparing this earlier photo of Bumstead, you can also see that his lower inner triceps were less developed and appeared more tendinous which, as will be discussed, actually contributes to the perception of short biceps, as does poor development of the pronator teres muscle and forearms to some degree. The pronator teres is a muscle that isn’t discussed much in bodybuilding, but you can see it on most bodybuilders. When developed, it fills in the area below the forearm and near the biceps.
Schwarzenegger’s outer biceps head was clearly more developed and so was his brachialis, which is under the biceps and adds to the appearance of biceps. As seen in this illustration, from the front, the brachialis appears as a thin strip under the biceps that runs into the coracobrachialis. In this illustration, the brachialis and the coracobrachialis appear to separate the biceps from the triceps. From the back the brachialis is much more visible than from the front. On a Schwarzenegger back double biceps pose, the brachialis is massive and fills in some of the area between the forearm and outer biceps. The brachialis is less developed on Bumstead but, if more developed, would help his back double biceps appearance.
You can also see here in Bumstead’s back double biceps that his brachioradialis muscle is bowing out to close the biceps gap a bit. In this photo of Nick Walker, his brachioradialis is actually behind the biceps. Talk about closing the gap between biceps and forearm. Ultimately, Bumstead’s outer biceps could stand more development but this demonstrates that there are other factors which contribute to short looking biceps, other than the biceps actual attachment.
Going back to the front double biceps, on Schwarzenegger you can see how the medial head of his triceps, the area closer to his elbow, appears less tendinous and more developed than with Bumstead. And that lower triceps mass clearly slides into his biceps and the long head of his triceps. With Schwarzenegger, there are three clear components of his upper arms appearance from the front. His biceps, his medial head of the triceps, and the triceps long head. With Bumstead, the medial triceps head is lacking, appearing tendinous, not very clear, and since it’s in close proximity to his biceps tendons, it creates the appearance of more tendon to the tendinous region on his biceps. If his medial triceps and long head were more developed, it would create a rounder, fuller, less angular look to his double biceps pose. You can see from his younger photo to his 2021 Mr Olympia image how much he developed his biceps and triceps. He still has the capacity to improve further. His genetics aren’t standing in his way of improving the size of his medial triceps head or outer head of his biceps. Notice that Bumstead’s pronator teres is so developed that it adds an extra component to the mix. Schwarzenegger’s pronator teres is less of a distraction and blends in with the rest of his forearm.
It’s hard to tell whether or not Bumstead sustained an injury to that area of his arm. In his younger photo he seems to have an added bump near that area of his left arm, if not on his pronator teres muscle. It’s uncertain whether or not added forearm flexor development could blend his forearm and pronator teres somewhat so he doesn’t have what appears to be a bump on his arm.
Here is a morph of Chris Bumstead’s actual arm photo and slight improvements added by making the outer biceps slightly more developed as well as adding more to his medial and long head of his triceps, adding a little forearm flexor development, and more development to his brachioradialis, although not to the Nick Walker level as shown previously. Notice how little biceps was added and that most of the added muscle was triceps.
Finally, here’s a morph from Bumstead to Schwarzenegger. There are a lot of small differences in the camera angle, camera lens, arm positioning, et cetera, so that this is not as direct a comparison as it could be, but you can notice some of the things discussed as the arms morph back and forth and make your own observations as well. Schwarzenegger’s taller outer biceps stands out as perhaps the biggest difference but a better analysis could be made from morphing 3D models that are in the exact same position, captured with the same virtual lens and, having a 3D art background, that’s in the realm of possibilities for this channel.