Bicep Curls: Unilateral vs. Bilateral, Advantages, and How to Optimize Your Workout

Is it better to curl one arm at a time?

Neither method is inherently "better" than the other; both unilateral (one arm at a time) and bilateral (both arms simultaneously) bicep curls offer distinct advantages depending on your specific training goals, current physical condition, and desired outcomes.

Introduction to Bicep Curl Variations

The bicep curl is a foundational exercise for developing strength and hypertrophy in the biceps brachii, brachialis, and brachioradialis muscles of the upper arm. While the fundamental movement pattern remains consistent, a common question arises regarding execution: should you curl both arms simultaneously (bilateral) or one arm at a time (unilateral)? Understanding the biomechanical and physiological implications of each approach is crucial for optimizing your training.

Understanding Unilateral Curls (One Arm at a Time)

Unilateral bicep curls, performed with a single dumbbell or cable attachment, require the non-working arm to remain still or support the body, allowing for isolated work on one side.

Key Advantages of Unilateral Curls:

• Improved Mind-Muscle Connection: By focusing on one limb, you can enhance proprioception and neural drive to the target muscle, often leading to a more effective contraction and greater muscle activation.
• Addressing Muscular Imbalances: Most individuals have some degree of strength or size asymmetry between their dominant and non-dominant limbs. Unilateral training allows you to identify and specifically strengthen the weaker side, promoting balanced development and reducing injury risk.
• Enhanced Core Stability and Anti-Rotation: When curling one arm, your core musculature (obliques, transverse abdominis, erector spinae) must work harder to prevent rotation and lateral flexion of the torso, acting as an anti-rotational and anti-lateral flexion stabilizer. This translates to improved functional strength and athletic performance.
• Greater Focus on Form: With only one arm working, it's often easier to maintain strict form, reduce momentum, and ensure the bicep is performing the majority of the work without compensatory movements from other muscle groups.
• Increased Time Under Tension (for the working arm): While the overall set might take longer, the individual working arm experiences more time under tension per set compared to a bilateral curl where both arms share the load and rest.

Potential Disadvantages of Unilateral Curls:

• Takes More Time: To achieve the same total volume as bilateral curls, unilateral training effectively doubles the time spent on the exercise, as each arm must be worked independently.
• Potentially Lower Overall Training Volume (per session): Due to time constraints, some individuals might reduce the total number of sets or repetitions across both arms during a unilateral session compared to what they could achieve bilaterally.
• Requires More Concentration: The need to stabilize the body and focus on one limb can be more mentally demanding.

Understanding Bilateral Curls (Both Arms Simultaneously)

Bilateral bicep curls involve lifting weight with both arms at the same time, typically with a barbell or two dumbbells.

Key Advantages of Bilateral Curls:

• Time Efficiency: Bilateral curls allow you to complete your bicep training in half the time compared to unilateral curls, making them ideal for individuals with limited workout duration.
• Higher Overall Training Volume (per session): Because both arms are working concurrently, you can often accumulate more total repetitions or sets in a shorter period, which can be beneficial for hypertrophy.
• Greater Systemic Load: With two arms working, you can generally lift more total weight than you could with a single arm. This can be advantageous for stimulating strength adaptations, though the load per arm might be less than what a single arm could handle in isolation.
• Simplicity and Accessibility: Bilateral movements are often more straightforward to set up and execute, especially for beginners or those using barbells.

Potential Disadvantages of Bilateral Curls:

• Potential for Compensatory Movements/Cheating: When both arms are working, it's easier for the dominant arm to compensate for the weaker arm, or for the back and shoulders to assist in the lift, reducing the isolation on the biceps.
• Masks Muscular Imbalances: If one arm is significantly weaker, it may contribute less to the lift, but this imbalance goes unnoticed as the stronger arm picks up the slack.
• Reduced Core Engagement: With a stable base and two points of contact, the core stabilizing demands are typically lower compared to unilateral movements.
• Less Focus on Individual Arm Performance: It's harder to gauge the effort and contraction quality of each bicep independently.

The Role of Specificity: When to Choose Which

The "better" method truly depends on your specific training objectives:

• For Addressing Muscular Imbalances: Unilateral curls are superior for identifying and correcting strength or size discrepancies between your arms.
• For Maximizing Hypertrophy (Muscle Growth) and Strength (Efficiently): A combination of both is often optimal. Bilateral curls can help you move heavier loads and accumulate high training volume quickly, while unilateral curls ensure balanced development and strict form.
• For Enhancing Core Stability and Functional Strength: Unilateral curls are excellent for improving core engagement and anti-rotational strength, which has carryover to many athletic movements and daily activities.
• For Beginners Learning Form: Starting with lighter unilateral curls can help beginners develop a stronger mind-muscle connection and understand proper bicep isolation before progressing to heavier bilateral lifts.
• For Advanced Athletes/Bodybuilders: Incorporating both methods strategically allows for comprehensive development, targeting different adaptations and preventing plateaus.

Integrating Both into Your Routine

A well-rounded training program will often include both unilateral and bilateral exercises. Here are a few strategies for integration:

• Alternating Cycles: Dedicate specific training blocks or mesocycles to primarily unilateral or bilateral work.
• Supersets/Combinations: Perform a bilateral exercise (e.g., barbell curls) followed by a unilateral variation (e.g., dumbbell hammer curls) in the same workout or as a superset.
• Prioritization: Start your bicep workout with unilateral movements to address imbalances and ensure quality work on each arm, then follow with bilateral movements for higher volume and heavier loads.
• Weak Link First: If you have a noticeable imbalance, always start with your weaker arm on unilateral exercises to ensure it receives adequate stimulus before fatigue sets in.

Proper Form Remains Paramount

Regardless of whether you choose unilateral or bilateral curls, proper form is non-negotiable. Avoid swinging the weight, using momentum from your back or shoulders, or allowing your elbows to drift excessively forward or backward. Focus on a controlled concentric (lifting) phase and an equally controlled eccentric (lowering) phase to maximize muscle activation and minimize injury risk.

Conclusion

There is no single "better" way to curl your arms. Both unilateral and bilateral bicep curls are effective tools in your strength training arsenal, each offering unique benefits. Unilateral training excels in addressing imbalances, enhancing core stability, and fostering a strong mind-muscle connection. Bilateral training provides efficiency, allows for higher overall volume, and can facilitate lifting heavier combined loads. For comprehensive development and to continually challenge your muscles, the most effective strategy is often to incorporate both methods into your training program, strategically choosing based on your current goals and individual needs.