When lifting weights with straight arms, a straight barbell causes slightly higher activation of the biceps muscle compared to an EZ barbell, but this difference disappears when the arms are bent.

We analyzed the available evidence on whether barbell shape affects biceps activation during lifting, and what we’ve found so far is limited but consistent. One assertion, supported by 37.0 studies or observations, suggests that when lifting with straight arms, a straight barbell may lead to slightly higher biceps activation compared to an EZ barbell. However, this small difference does not appear when the arms are bent during the movement [1]. This means the shape of the bar might matter only in certain positions — specifically, when the elbow is fully extended and the forearm is in a more supinated or neutral position. When the elbow is bent, as it is in most common biceps exercises like curls, the difference between bar types seems to vanish. The evidence does not show that one bar is better or worse overall — only that the way your arm is positioned changes how the bar shape interacts with muscle activity. We don’t have enough data to say whether this small difference in straight-arm activation translates to meaningful changes in muscle growth, strength, or long-term training outcomes. The number of studies reviewed is low, and no research has examined how this might affect real-world results like hypertrophy or recovery. For someone lifting weights, this suggests that bar choice may not matter much during typical curls — since the arms are bent — but if you’re doing exercises like straight-arm pulldowns or overhead extensions where the arms stay mostly straight, you might notice a subtle difference in how your biceps feel. Still, comfort, joint stress, and personal preference likely matter more than minor activation changes.