A Barbell Curl a weight training exercise which targets the biceps brachii muscle in order to develop one or more of the following attributes:

• size
• definition
• strength
• stamina
• length

Target Muscles

Target

• Biceps Brachii

Synergists

• Brachialis
• Brachioradialis

Stabilizers

• Deltoid, Anterior
• Trapezius, Upper
• Trapezius, Middle
• Levator Scapulae
• Wrist Flexors

• Stand with your feet apart for a firm base.
• Grasp bar with a shoulder width under hand grip.
• Keep your chest high and your shoulders down and back.
• Keep your knees slightly bent in order to take stress off your lower back.
• Without swaying, swinging or lifting at the shoulders and keeping your upper arms at your sides, curl the barbell up in a wide arc from your thighs up to shoulder level until forearms are vertical.
• Squeeze the biceps.
  
• Lower the weight in a controlled fashion until arms are fully extended.
  
• Repeat.

Tips  when Performing Barbell Bicep Curls

• The key to the bicep curl is weight control. If you can't control the weight through the whole bicep curl, you may be lifting too heavy.
• Take a narrow grip (inside shoulder-width). This activates the biceps more strongly than a shoulder-width or outside shoulder-width grip. You will not be able to use as much weight as with a wider grip but you will get increased bicep muscle recruitment during the movement.
• You can take advantage of the improved leverage on the wide grip by first doing a set to failure in a narrow grip then immediately switching to a wider grip and continuing till failure with that grip.

• Swinging the weight. This error is often made by people who are using too much weight in an effort to use momentum to get the weight moving. This reduces the effectiveness of the exercise by taking tension off the target muscles. It also has the potential to damage your lower back.
• Overarching the back. The other common error is hyperextending (over-arching) the back. This places an unnecessary strain on the lower back.
• Leaning back. This is often done at the end of the set as the weight starts to get heavy in an effort to keep going. This is potentially dangerous to your lower back. If you can't complete the rep in the good form, go as far as you can, hold it there for as long as you can, then lower the weight.
• Not wearing a lifting belt. This places an unnecessary strain on the lower back.

Incorrect form may lead to multiple types of injuries including:

• Torn ligaments/tendons in lower back, biceps.

Variations are intended to work different subgroups of muscles, or work the same muscles in slightly different ways. Biceps curls can be done using any of the following equipment:

• Dumbbell(s)
• Barbell
• E-Z bar (also known as a "Bent bar")
• Cable machine
• Biceps curling machine

Although the exercises differ, a common factor of each is a 'curling' motion, where a weight—attached to an item of equipment listed above—is moved through an arc, primarily using the strength of the biceps. The bicep is contracted to lift the weight upward through the arc, to a point where further movement is not possible. The biceps is then extended, lowering the weight back through the arc, to the start position. This contraction and extension together constitute a single repetition.