When people train one leg at a time, that leg gets much stronger than the other leg, even if the other leg didn’t do any training.

Scientific Claim

Twelve weeks of progressive heavy resistance training is associated with a 17% increase in unilateral 1 RM strength in the trained leg and a 10–11% increase in the untrained leg among individuals performing unilateral training, indicating greater transfer of strength gains to the trained limb.

Original Statement

“The average relative increases of 17±11% (P<0.001) and 14±14% (P<0.001) in unilateral 1 RM values of the right and left leg in all UNIL trained subjects were greater (P<0.05) than those of 10±18% (P<0.001) and 11±11% (P<0.001) recorded for all BIL trained subjects, respectively.”

From study:Neuromuscular adaptations during bilateral versus unilateral strength training in middle-aged and elderly men and women.

Evidence Quality Assessment

Claim Status

overstated

Study Design Support

Design cannot support claim

Appropriate Language Strength

association

Can only show association/correlation

Assessment Explanation

The study design lacks confirmed randomization, so causal claims about 'producing' or 'leading to' specific transfers are unsupported. Only associations can be stated.

More Accurate Statement

“Twelve weeks of progressive heavy resistance training is associated with a 17% increase in unilateral one-repetition maximum (1 RM) strength in the trained leg and a 10–11% increase in the untrained leg among individuals performing unilateral training, indicating greater strength gains in the trained limb.”

Evidence from Studies

Supporting (0)

No supporting evidence found

Contradicting (1)

Neuromuscular adaptations during bilateral versus unilateral strength training in middle-aged and elderly men and women.

Randomized Controlled Trial

Human

1996 Sep

The study found that when people trained one leg, both the trained and untrained leg got stronger — almost equally — so the claim that the trained leg gets much stronger isn’t backed up.

Source Study

Neuromuscular adaptations during bilateral versus unilateral strength training in middle-aged and elderly men and women.

Score: 46

DOI: 10.1046/j.1365-201x.1996.523293000.x

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