Analysis Version
v1
History
Back to Study: Small muscle mass exercise enhances muscular adapt...
causal
Analysis v1
61
Pro
0
Against

Doing bicep curls with one arm makes that arm stronger for one-arm curls, but doesn’t make you stronger for two-arm curls or the other arm.

Scientific Claim

In untrained young women, the magnitude of strength adaptation from unilateral biceps curl training is specific to the trained movement pattern and does not translate to improved bilateral strength or contralateral limb strength.

Original Statement

“U-BC exhibited greater changes in 1RM UNI right arm [∆ 0.75 (0.22, 1.27) kg], but no between-group difference was observed in 1RM UNI left arm [∆ 0.43 (-0.24, 0.93) kg]. The 1RM BIL changes were not different between groups [∆ -0.28 (-1.23, 0.66) kg].”

From study:Small muscle mass exercise enhances muscular adaptations? Effects of unilateral and bilateral biceps curl on maximum strength and muscle size changes.

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 directly tested multiple strength outcomes (bilateral, left unilateral, right unilateral) and found differential effects, allowing definitive conclusions about movement- and limb-specific adaptation.

Evidence from Studies

Supporting (1)

61
61

Small muscle mass exercise enhances muscular adaptations? Effects of unilateral and bilateral biceps curl on maximum strength and muscle size changes.

Randomized Controlled Trial
Human
2025 Dec 8

People who trained one arm at a time got stronger in that arm, but not much stronger in the other arm or when using both arms together — so training one side doesn’t automatically help the other side or both sides at once.

Contradicting (0)

0
No contradicting evidence found

Source Study

Small muscle mass exercise enhances muscular adaptations? Effects of unilateral and bilateral biceps curl on maximum strength and muscle size changes.

Score: 61
DOI: 10.1007/s00421-025-06033-4

Similar Assertions

Training your right arm alone makes your right arm stronger, but doesn’t help your left arm get stronger — the benefit stays on the side you trained.

61
0
92%

Training one arm at a time doesn’t make you stronger when lifting with both arms together — your total strength gain is the same as training both arms at once.

61
0
88%

Doing bicep curls one arm at a time makes your right arm stronger than doing them with both arms together, but doesn't make your biceps bigger than using both arms.

61
0
82%

Whether you lift weights with one arm or both at the same time, your biceps grow about the same amount after 8 weeks of training.

61
0
78%

Training one arm with heavy eccentric curls makes the other arm stronger too—even though it didn’t lift any weights—by about 10%, while the trained arm gets even stronger, by nearly 20%.

46
0
75%