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.

Scientific Claim

Twelve weeks of unilateral knee extension training in young, recreationally active women increases unilateral isometric strength by 21.4% and muscle electrical activity in the quadriceps by 39.9%, significantly more than bilateral training, which shows only 10.3% and 12.0% increases, respectively, indicating that unilateral training specifically enhances neural activation and strength in the trained limb.

Original Statement

“The UG demonstrated greater unilateral isometric strength increase than the BG (21.4 ± 10.5% vs. 10.3 ± 11.1%, respectively) and only the UG increased muscle electrical activity.”

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 study is a randomized controlled trial with pre-post measurements and statistical significance (p ≤ 0.05), allowing definitive causal claims within the studied population and exercise.

Evidence from Studies

Supporting (1)

Neuromuscular Adaptations to Unilateral vs. Bilateral Strength Training in Women

Randomized Controlled Trial

Human

2016 Jul

This study found that training one leg at a time made that leg stronger and more electrically active than training both legs together, which is exactly what the claim says.

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

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.

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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.

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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.

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If you train one leg at a time, that leg gets much stronger than the other when tested alone — but if you train both legs together, both legs get stronger at the same rate, with no one leg getting ahead.

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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.

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