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Bilateral vs. Unilateral Bicep Curls: Strength Comparison

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Unilateral (One Arm at a Time) Curls

• You can usually lift slightly more per arm in a unilateral curl.
• This is partly due to:
  • Greater neural drive (you can focus all effort on one limb).
  • Less systemic fatigue since only one arm is working.
  • Core and stabilizers assisting more, especially in standing variations.

Example:

If you curl 40 lbs for 8 reps with one arm at a time, you might only manage 35–37.5 lbs per arm during bilateral curls with good form.

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Bilateral (Both Arms at Once) Curls

• You typically lift more total weight overall, but less per arm compared to unilateral.
• The movement is more time-efficient and symmetrical.
• Slight cheating (like using momentum) is easier to sneak in, which can increase the load artificially.

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Why You Might Lift More Per Arm Unilaterally

• Your central nervous system can concentrate force production on just one limb.
• No bilateral deficit: Many people experience a slight reduction in per-limb output when using both limbs simultaneously (called the bilateral deficit).
• Improved focus and mind-muscle connection.

🔄 Practical Implication

• If your goal is maximum load per arm and improved control, unilateral curls may be superior.
• If you’re training for efficiency, symmetry, or overall volume, bilateral curls are excellent.

💡 Pro Tip:

Alternate both styles in your routine:

• Use bilateral curls early for volume and symmetry.
• Finish with unilateral curls to focus on peak contraction and correct imbalances.