Health Claims

If new gym guys do a specific arm curl workout for 10 weeks — going until their muscles are totally tired — their biceps get about 7% to 9% thicker, no matter how their shoulders are positioned, as long as the movement and resistance stay the same.

If you're new to lifting, changing your arm position during cable curls doesn't make one part of your biceps grow more than another — both positions give you the same kind of muscle growth over 10 weeks if everything else is kept equal.

If you do cable curls the same way every time except for where your shoulders are, it doesn’t really matter for building arm muscle—even if you can lift heavier when your arms are stretched out.

If new guys do a specific arm curl workout for 10 weeks — going until their muscles are totally tired — their arm muscles get about 7% to 9% thicker, no matter how their shoulders are positioned, as long as the movement and resistance stay the same.

If you're new to lifting and do cable curls the same way each time, it doesn't really matter whether your arms are stretched far back or in a neutral position — your biceps will grow about the same amount after 10 weeks.

If you're used to lifting weights, changing the angle of your arm during bicep curls in one workout can make your muscles work harder—even though you're doing the same amount of lifting.

After a bicep workout, your muscle swells up right away — by about 12% — but that puffiness goes away within a day, even if you changed up your arm angles during the workout.

Changing your shoulder angle while doing bicep exercises seems to cause more muscle swelling and strain in the lower part of your bicep right after the workout, especially if you do moves that stretch the muscle.

If you're used to lifting weights, changing the angle of your shoulder during bicep curls doesn't make your workout easier or harder — you still do about the same amount of work as with a fixed angle.

Changing the shoulder angle during bicep curls makes your biceps work harder, even if you're lifting the same total weight — your muscles fire more, according to electrical activity measurements.

This scan can see how stiff your biceps get before and after a workout, and might help track muscle changes without needles or surgery — especially for guys who lift weights regularly.

If you're into weight training, where you position your shoulder affects how stretched your biceps are and how stiff they feel before exercising — especially when your arm is pulled back behind you.

After heavy bicep workouts, most guys show reduced muscle stiffness in a specific part of the bicep—especially when the arm is stretched out—meaning that area might get worked harder during certain movements.

If young women do bicep curls on an incline bench, they’ll likely grow the upper part of their biceps more, but if they use a preacher curl bench, they’ll grow the lower part more — the way you curl matters for where your muscle grows.

Young women who do incline bicep curls twice a week for 8 weeks get stronger at that exact move compared to doing preacher curls — it looks like getting stronger depends on the specific exercise you do.

If young women do preacher curls twice a week for 8 weeks, they get stronger at that specific move compared to doing incline curls — it really helps to train the way you want to get strong.

For young women doing strength training twice a week, preacher curls might build more muscle in the lower part of the biceps than incline curls.

Young women who train biceps twice a week for 8 weeks get stronger in the exact curl they practice—like getting better at preacher curls if they do preacher curls. It shows your muscles get best at what you actually train.

If young women do preacher curls instead of incline curls during their workouts for 8 weeks, they’ll likely build more muscle in the lower part of their biceps.

If young women do incline bicep curls twice a week for 8 weeks, their upper arm muscles grow more than if they did preacher curls — the type of curl really affects where the muscle grows.

Ultrasound can reliably measure arm muscle size in active women, and the same person can get consistent results when repeating the measurement—making it a trustworthy way to track muscle growth from workouts.

For women who work out regularly, doing preacher curls or incline bicep curls doesn't seem to change where their biceps grow — both exercises lead to similar growth patterns after 9 weeks.

Doing inclined bicep curls 3 times a week for 9 weeks doesn’t seem to make women’s biceps grow more in specific areas, even when they push themselves to the max each time.

Doing preacher curls might help women who work out regularly build more arm muscle, especially toward the lower part of the upper arm, and after about 9 weeks they could see around a 9% increase.