Switching up your shoulder position during bicep curls makes your muscles fire more, even if you're lifting the same total weight.

Scientific Claim

Muscle activation during biceps curls is higher when glenohumeral joint angles are varied across sets compared to a fixed neutral position, even when volume load is matched, suggesting that movement variation enhances motor unit recruitment.

Original Statement

“Our results demonstrated that VAR condition produced greater total muscle activation compared to CON (e.g., 95%-CI: 8.4% to 23.3%, p = 0.0001).”

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 EMG normalization and statistical significance supports definitive causal language for acute neuromuscular response.

Evidence from Studies

Supporting (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

When people did bicep curls with their arms in different shoulder positions during the workout, their biceps worked harder overall than when they kept the same position the whole time—even though they lifted the same total weight.

Contradicting (0)

No contradicting evidence found

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

Changing the angle of your shoulder while doing bicep curls makes your biceps work harder during the workout, even if you're lifting the same total weight.

86%

Even when you change your shoulder position during bicep curls, you still lift the same total amount of weight — your total workout effort doesn’t go up or down.

83%

Just because changing your shoulder angle makes your biceps work harder during one workout doesn’t mean it will make your muscles bigger over time — this study didn’t test that.

83%

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

79%