Whether you change your shoulder angle or not during bicep curls, your muscles recover at the same speed over the next three days.

Just because changing your shoulder angle makes your biceps work harder during one workout doesn’t mean it will make your muscles bigger over time — this study didn’t test that.

Even when you change your shoulder position during bicep curls, you still lift the same total amount of weight — your total workout effort doesn’t go up or down.

When you do bicep curls with your shoulder stretched back, the lower part of your bicep shows more signs of stress on ultrasound right after the workout than when you keep your shoulder neutral.

The middle part of your bicep gets a little more 'hazy' on ultrasound after a workout, but it clears up by the next day — and it doesn’t matter if you changed your shoulder angle.

Switching up your shoulder position during bicep curls makes your muscles fire more, even if you're lifting the same total weight.