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If the goal is to emphasize the bicep muscles, hands should be placed in full supination (palms up).
If a straight bar is used, requiring full supination, the grip width is determined by your carrying angle.
To determine your carrying angle, stand with hands at your sides, palms facing the body.
From this position, forearms (not shoulders) should be rotated outward, indicating ideal placement for hands on the bar.
Because some people feel discomfort when fully supinated, the use of a barbell may not be appropriate.
Variations of resisted elbow flexion can be achieved by altering shoulder positions.
By altering the starting length of the biceps, new effects can be created.
Examples of variations include the incline dumbbell curl in shoulder extension (shoulder behind the body) and the concentration curl in shoulder flexion (shoulder in front of the body).