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House of Hypertrophy

TL;DR

The evidence shows mixed support for shoulder-extended curls being superior to preacher curls for biceps growth, with some studies favoring incline curls for upper biceps development while others show no difference.

We checked the science

our breakdown of the video

10 claims, each mapped to its moment in the video

When you move your arm backward, it stretches your biceps because the muscle runs over your shoulder joint — and when you move your arm forward, the biceps gets shorter.

Multiple causal studies (RCTs / meta-analyses) support this claim.

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Just because a study doesn’t find a clear difference in arm muscle growth between two curl types, it doesn’t mean there isn’t a real difference — the study might just be too small to catch it.

Multiple causal studies (RCTs / meta-analyses) support this claim.

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Small studies might miss real differences just because they don’t have enough people in them — it’s like trying to hear a whisper in a noisy room.

Strong evidence from clinical studies backs this claim.

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Doing bicep curls on an incline bench builds more muscle in the upper part of your biceps than preacher curls do.

Strong evidence from clinical studies backs this claim.

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Doing preacher curls might build more muscle in a specific lower part of your upper arm than incline curls do.

Strong evidence from clinical studies backs this claim.

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Doing bicep curls on an incline bench might build your biceps muscle better than doing preacher curls, especially in the middle part of your upper arm.

Strong evidence from clinical studies backs this claim.

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If you do leg extensions while leaning back, it might build more muscle in the top part of your front thigh compared to doing them upright.

Evidence contradicts this claim.

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If you stretch your hips back while doing leg extensions, your quad muscle gets longer and grows more—especially in the middle and upper parts—than if you do the exercise with your hips bent.

Evidence contradicts this claim.

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Working your biceps with your arms stretched back might grow the upper part of the muscle a bit more than doing curls with your arms already in front of you.

Evidence contradicts this claim.

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If you mix up your workouts for the same muscle, you’ll grow that muscle more evenly than if you always do the same exercise.

Evidence contradicts this claim.

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Key Takeaways

  1. 1Problem: It's unclear which biceps exercise—preacher curls or shoulder-extended curls like incline or Bayesian curls—is best for building bigger arms.
  2. 2Core methods: Shoulder-extended curls (e.g., incline dumbbell curls, Bayesian cable curls), preacher curls (shoulder-flexed position), resistance profile matching, regional muscle measurement, and comparison across multiple studies.
  3. 3How methods work: Shoulder-extended curls stretch the biceps more because the arm is behind the body, which may help it grow better, especially in the upper part. Preacher curls shorten the biceps and may better target the brachiialis. Matching resistance ensures fair comparison, and measuring different muscle regions shows where growth happens.
  4. 4Expected outcomes: Shoulder-extended curls may lead to slightly more biceps growth, especially in the upper portion, while preacher curls may better develop the brachiialis and brachioradialis. Overall, both work, but extended-position curls might have a small edge.
  5. 5Implementation timeframe: Results observed after 8–10 weeks of consistent training, 2–3 times per week with 3–5 sets of 8–12 reps to near failure.

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