I am absolutely loving how the most simple topic of "How to grow arms" can fuel so much good discussion. "The most basic things take the longest to master." The reality is that neither one of us are disagreeing with the other. I think you can build an above average, strong, highly athletic physique with only 4 exercises - chins, dips, squats, and deadlifts.
I think I could argue that the first 6 months of someone's training career can be benefited by any kind of training so long as the trainer is working hard. You could do nothing but squats 4 days a week and your upper body will grow during those first 6 months. Your back will get thicker, your core will strengthen, your traps will respond to the weight of the bar pressing into them, your chest and shoulders will develop from being so taught at the bottom of the rep, your neck will thicken from the strain of pushing, your hands will get stronger from loading the plates onto and off the bar, etc. So whether you do 3 sets of barbell curls for 10 reps or a highly specialized bicep workout featuring 5 different exercises for 3 sets each that hit the bicep from a variety of angles and emphasize full range of motion, your biceps will grow in those first 6 months. I personally think that if bodybuilding is the goal, then emphasizing isolation work right out of the gate is the best way to go. It doesn't make sense to start prioritizing the mind muscle connection after the first year of basically just throwing around weight. It's safer and more effective to emphasize learning how to contract your muscles optimally from day one. And the best way to learn that skill is through isolation work.
Another point I want to bring up is that there are no compound movements for the biceps. Bicep contraction is achieved through elbow flexion. There's only one joint involved. The forearms are involved in all bicep exercises, but they're also involved in everything that requires us to hold something. A compound exercise is defined as: any exercise that engages two or more different joints to fully stimulate entire muscle groups and, indeed, multiple muscles. Only dips and close grip bench presses are compound movements associated with triceps training because they involve elbow flexion and shoulder extension. 90% of upper arm training falls under isolation work.
The argument then is whether or not compound movements are the most effective way for beginners to build muscle. If that is true then you'd have to be willing to tell someone not to specifically target their upper arms during their initiation into weight training. This is dependent on goals. Should high school freshman trying out for football incorporate db curls and tricep pushdowns into their first weight training program? The science points to no because isolation work is going to work against the body functioning as a single unit. When you tackle someone, you don't use your lats or your pecs, you use your entire body. The body then must develop the skill of acting synergistically with itself. This helps avoid injury on the field. Athletes should train with almost exclusively compound movements and sport specific movements.
But if body composition is the goal, and most people who start training have an initial goal of increasing their arm size (as per OP) then specifically targeting the arms should not only be a necessity, but a priority. If arm training is made a priority then emphasizing peak contraction and a full stretch through a variety of angles with reps in the 8-15 range is going to be the most effective plan for both developing the skill of optimally contracting the muscle and building size.
I'm off to win Becky Thatcher's heart.
