In a study they looked at the muscle activation of the bicep brachii and the brachioradialis muscle in each of variation.
In this study, they did 10 reps at 65% of their 1 RM and looked at the concentric and eccentric. They did 3 seconds a rep. They observed the subject’s trunk muscles and knees to make sure they weren’t cheating on these reps.
🔥Muscle Activation
 During the EZ bar curl and the barbell curl, they found that the bicep brachii and brachioradilais muscle had a slightly lower activation compared to the EZ bar curl but it was not significant.
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🔥Overall
 The concentric phase of the lift had a greater activation in general while the eccentric phase had a lower activation overall. The EZ bar curl was most effective at activating the bicep brachii and brachioradilis. The reason this may be for the high activation could be due to the semiproned grip.
🔥Eccentric Phase
 The brachioradilails activation compared between exercises was not significantly different.
The EZ curl and the barbell curl have very slight differences, so it may just end up being a matter of comfort as to which one you choose.
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One exercise is not necessarily better than the other
Let me know in the comments your thoughts! No questions is stupid! Just ask!
Resource:
Differences in electromyographic activity of biceps brachia and brachioradilais while performing three variants of curl!
