When you do bicep curls with your shoulder stretched back, the lower part of your bicep shows more signs of stress on ultrasound right after the workout than when you keep your shoulder neutral.

Scientific Claim

Echo-intensity in the distal region of the biceps brachii increases more after resistance training with varied glenohumeral angles than with constant angles, suggesting greater localized muscle strain or fluid accumulation in the lengthened position.

Original Statement

“For distal echo-intensity (DEI), there was a significant main time effect (p = 0.0001)... ES analysis suggests that magnitude of effect was larger in the VAR when compared to CON condition (ES; 1.04 vs. 0.60), respectively.”

From study:The Effects of Varying Glenohumeral Joint Angle on Acute Volume Load, Muscle Activation, Swelling, and Echo-Intensity on the Biceps Brachii in Resistance-Trained Individuals

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 quantitative ultrasound analysis and effect size comparison supports a definitive causal claim for acute strain differences in the distal biceps.

Evidence from Studies

Supporting (0)

No supporting evidence found

Contradicting (1)

The Effects of Varying Glenohumeral Joint Angle on Acute Volume Load, Muscle Activation, Swelling, and Echo-Intensity on the Biceps Brachii in Resistance-Trained Individuals

Randomized Controlled Trial

Human

2019 Sep 4

The study found that changing arm angles during bicep curls made muscles work harder, but it didn’t find that one part of the muscle got more swollen or strained than another — so the claim about extra strain in stretched positions isn’t backed up.

Source Study

The Effects of Varying Glenohumeral Joint Angle on Acute Volume Load, Muscle Activation, Swelling, and Echo-Intensity on the Biceps Brachii in Resistance-Trained Individuals

Score: 51

DOI: 10.3390/sports7090204

Similar Assertions

The middle part of your bicep gets a little more 'hazy' on ultrasound after a workout, but it clears up by the next day — and it doesn’t matter if you changed your shoulder angle.

92%

Doing bicep curls with your arm stretched behind you makes the lower part of your bicep feel more strained right after the workout than doing them with your arm at your side.

89%

Whether you change your shoulder angle or not during bicep curls, your muscles recover at the same speed over the next three days.

80%

After a tough bicep workout, your arm gets a little swollen, but it goes back to normal by the next day — and it doesn’t matter if you changed your shoulder angle during the workout.

79%

The second time people do a tough arm workout, their muscles show less 'swelling' on ultrasound scans, meaning there's probably less damage or inflammation.

78%