If you’re into strength training, working to build muscle and gain strength, you might have wondered whether unilateral exercises (working one limb at a time) or bilateral exercises (both limbs working together) are better for achieving your fitness goals.
Thanks to a recent systematic review and meta-analysis by Kassiano et al., published in the Sports Medicine journal, we now have a clearer picture of how these two approaches compare in terms of muscle growth and strength gains.1
Let’s unpack the findings and figure out what this means for your workouts.
Unilateral vs. Bilateral Exercises: What’s the Difference?
Unilateral Exercises
Unilateral exercises focus on one limb at a time, often requiring greater balance and stability. Examples include:
They are great for:
- Addressing muscular imbalances.
- Improving stability and coordination.
- Enhancing unilateral strength (duh).
Bilateral Exercises
Bilateral exercises work both limbs simultaneously, allowing for heavier loads. Think:
These exercises are often staples in strength training programs because they:
- Work large muscle groups at the same time.
- Allow for maximal force production.
- Promote tremendous strength development in large parts of the body,
A New Study: What Does the Science Say?
Kassiano et al.’s recent review included nine studies comparing unilateral and bilateral training methods. Here’s what the science revealed:
- Muscle Hypertrophy (Growth)
- Dynamic Strength Gains
Key Findings:
- Muscle Growth:
- Both unilateral and bilateral exercises are equally effective for muscle hypertrophy. The choice of exercise doesn’t seem to matter much when it comes to building muscle—both can lead to gains as long as training volume and intensity are high enough.
- Strength Gains:
- Bilateral Strength (e.g., squats): Bilateral exercises lead to greater improvements in bilateral strength. If you want to hit a personal record in your squat or deadlift, stick with bilateral training.
- Unilateral strength (e.g., split squats): Unilateral exercises are more effective for improving unilateral strength. Want to impress your date with how many single-leg pistol squats you can do, or want to get better at a sport that requires a lot of single-leg movements? Focus on unilateral training.
These findings align with the principle of specificity: training adaptations are specific to the type of movement you practice.
The Principle of Specificity
Strength adaptations follow the principle of specificity: you get better at what you train.
If you train both legs together (e.g., squats), you’ll see greater strength gains in movements requiring bilateral effort. Similarly, training one leg at a time boosts your unilateral strength more effectively.
- Bilateral exercises allow you to lift heavier weights and engage more muscle groups at once, leading to better bilateral strength gains. However, they can mask imbalances, as your dominant side may compensate for your weaker side.
- Unilateral exercises emphasize balance, coordination, and stability, often recruiting smaller stabilizing muscles. They also help address asymmetries and force each limb to work independently for balanced strength development.
Another factor is neural adaptation—your nervous system learns to optimize the movement patterns you practice. Bilateral exercises improve your ability to generate force using both limbs together, while unilateral exercises fine-tune your ability to stabilize and move with one limb.
Practical Takeaways: What Should You Do?
Here’s how to apply these findings to your workout routine:
- For Strength Goals:
- Prioritize bilateral exercises (e.g., squats, deadlifts, rows, and bench presses) if your goal is to lift heavier weights.
- Include some unilateral exercises as accessory movements to address imbalances and improve stability.
- For Muscle Growth:
- Both styles are equally effective, so choose based on your preferences or needs. If you enjoy split squats and find them challenging and fun (yeah, right), they can work just as well as back squats for building muscle.
- For Athletic Performance:
- Build a foundation of strength with compound bilateral movements like squats, but also incorporate unilateral exercises into your routine.
- Many sports involve single-limb actions (think kicking, throwing, or running), and unilateral training can improve your performance beyond what staying with only good old squats and bench presses can.
- For Any Goal:
- If you’re short on time, bilateral exercises allow you to train multiple muscle groups quickly.
- If you’re rehabbing an injury or correcting imbalances, unilateral exercises can be the best option.
Why Not Both?
Why not both indeed.
Personally, I have a love/hate relationship with unilateral exercises. And I know plenty of others do, too. I know they are awesome, but they are often hard (and sometimes I’m a bit lazy in the gym), and once you’ve completed one side, you have one to go.
The good news is that you don’t have to choose one over the other
A well-rounded training program can (and probably should) include both unilateral and bilateral exercises. That way, you’re covering all bases—maximizing strength, improving balance and stability, and building muscle to the best of your ability.
- Bilateral exercises for maximal strength and efficiency.
- Unilateral exercises for balance, injury prevention, and sport-specific functionality.
- Whatever floats your boat for building muscle, as long as you can practice progressive overload and get close to muscular failure.
Final Rep
The key takeaway from this new meta-analysis is that both approaches are valuable depending on your goals. They each offer benefits that can help you gain more strength, muscle mass, and athletic prowess.
