Whether you train one leg or both legs at once for 12 weeks, your legs get just as big and strong overall — the way you do the exercise doesn’t change how much muscle you build or how strong you become in general.

Scientific Claim

Unilateral and bilateral knee extension training produce equivalent increases in overall muscle thickness (quadriceps) and dynamic strength (1RM) in young women after 12 weeks, demonstrating that training modality does not influence muscle growth or general strength gains in this population.

Original Statement

“Both UG and BG increased similarly their unilateral 1RM (33.3 ± 14.3% vs. 24.6 ± 11.9%, respectively), bilateral 1RM (20.3 ± 6.8% vs. 28.5 ± 12.3%, respectively), and isometric strength (14.7 ± 11.3% vs. 13.1 ± 12.5%, respectively). Muscle thickness increased similarly for both training groups.”

From study:Neuromuscular Adaptations to Unilateral vs. Bilateral Strength Training in Women

Evidence Quality Assessment

Claim Status

appropriately stated

Study Design Support

Design supports claim

Appropriate Language Strength

definitive

Can make definitive causal claims

Assessment Explanation

The RCT design with pre-post measurements and statistical analysis confirms no difference between groups for these outcomes, supporting definitive language about equivalence.

Evidence from Studies

Supporting (1)

Neuromuscular Adaptations to Unilateral vs. Bilateral Strength Training in Women

Randomized Controlled Trial

Human

2016 Jul

Both one-legged and two-legged leg exercises made women’s thighs equally thicker and their overall leg strength equally stronger after 12 weeks, so it doesn’t matter which one you pick if your goal is general muscle growth and strength.

Contradicting (0)

No contradicting evidence found

Source Study

Neuromuscular Adaptations to Unilateral vs. Bilateral Strength Training in Women

Score: 47

DOI: 10.1519/jsc.0000000000001125

Similar Assertions

Even though people who trained one leg at a time ended up lifting heavier weights than those who trained both legs together, both groups ended up with the same muscle size and overall strength — so lifting heavier with one leg doesn’t automatically make you stronger overall.

89%

Doing leg extensions one leg at a time for 12 weeks makes each leg stronger and more active when tested alone, better than doing both legs together — even though both methods improve overall leg strength similarly.

87%

Training one leg at a time makes it harder for both legs to work together at full power, while training both legs together makes them work better together — the way you train changes how your legs coordinate.

85%

To get stronger, it matters more how heavy the weight is than whether you push to your absolute limit—lifting heavier weights makes you stronger, no matter if you stop short of failure.

78%

Even if you only do squats, you still get almost as strong at leg extensions as someone who only does leg extensions—so squats aren’t useless for that movement.

78%