The Study
Mixing Up Muscle Lengths: The Effects of Training at Different Muscle Lengths in the Elbow Flexors
This study compares two types of arm curl exercises by testing both on the same people. It shows what happened during the study, but can't prove one method is better for everyone because it's small and we don’t know if the people or testers knew which exercise was which.
Analysis score
Maximum 90 for a randomized controlled trial.
Where the score came from
One arm did only long-muscle curls, the other did a mix of long and short curls. After 8 weeks, both got stronger and a bit bigger, but the long-muscle workout might have helped muscles grow a little more.
Where does this study sit?
Reviews of RCTs (Meta-analyses)
Max 100Randomized Trials
Max 90Reviews of Cohort Studies
Max 85Cohort Studies
Max 72Reviews of Case-Control Studies
Max 63Case-Control Studies
Max 58Cross-Sectional & Case Series
Max 50Expert Opinion
Max 547 / 100
Quality score
Participants are randomly assigned to treatment or control groups, minimizing bias. The gold standard for testing whether an intervention causes an effect.
Key takeaways
Summary
Based on the study abstract and findings.
- 1The muscle size and strength gains are real, but the difference between the two workouts is small and may not matter much in real life.
- 2Muscle size went up by 6.01 cm² in the long-length group and 3.18 cm² in the mixed group.
- 3The long-length group gained 0.89 mm more in arm thickness at the bottom of the arm.
- 4Strength went up by about 7 kg in both groups when doing long curls.
Score breakdown, methodology, conflicts of interest, evidence analysis & raw study data
Publication
Authors
Seth Hinson, Jacob F. Remmert, Zac P. Robinson, Joshua C. Pelland, Shawn Dinh, Ethan Elkins, Caitlyn Meehan, David Diaz, Brian Benitez, Christian Macarilla, Michael Morgan, Michael C. Zourdos
Related Content
Videos (2)
Claims (10)
When people who regularly lift weights perform exercises that stretch their muscles fully, they gain more strength in movements that involve those stretched positions, such as bending the elbow while the muscle is lengthened.
Doing resistance exercises with the elbow muscles stretched out or in varied positions leads to a measurable increase in the size of the elbow flexor muscles in people who regularly work out but are not elite athletes.
When performing resistance exercises that stretch the elbow flexor muscles more, the muscles grow larger in cross-sectional area than when the same exercises are done with less stretch.
When people who exercise recreationally train with their muscles stretched more during movements, they gain a bit more muscle size compared to training with varied muscle lengths, but both approaches lead to the same improvement in strength.
There is not enough scientific research yet to determine whether training muscles at longer or shorter lengths leads to better muscle growth.
When people who already train regularly perform resistance exercises until they can no longer complete another repetition, and they do enough total work, their muscles grow larger, no matter which exercises they choose.
Not medical advice. For informational purposes only. Always consult a qualified healthcare professional before making health decisions.