FAST-TWITCH, FAST-TWITCH, FAST-TWITCH :
Yes, your arms have a high amount of fast-twitch muscle fibers. So it makes sense that if you want to maximize the size of your arms, you must stress the fibers with the greatest growth potential.
The Brachialis :
While your biceps have a mix of fast and slow-twitch fibers, the misnamed "lower biceps" or brachialis is composed primarily of fast-twitch fibers. Even though it is only the size of a golf ball, the brachialis is situated underneath your biceps next to the inside of your elbow.
With regards to symmetry, this is a strategic location on your arm. Develop the brachialis, and its increased size will push the biceps up and give you greater biceps "peak." Greater bicep peak adds to greater arm girth.
The Triceps Long Head :
Of the three triceps heads (lateral, medial, and long head), the long head of the triceps is the meatiest of the three. Even when the lateral and medial heads are fully developed and the long head is underdeveloped, the long head is still comparable in size.
Whereas the lateral and medial heads have a mix of fast and slow-twitch fibers, the long head is comprised primarily of fast-twitch fibers. So when the fibers of the triceps long head are properly stressed, they develop tremendous size.
Set & Rep Protocols For The Upper Arms :
You know where the fast-twitch fibers are on your arms, and you know what exercises isolate these fibers. You can find the training partner appropriate for you on :
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