Iron Culture presented by MASS Ep 366 - New Studies: Long Muscle Lengths & Muscle Swelling
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Feb 18, 2026 They dissect new research on training at long muscle lengths and whether emphasizing stretched positions truly changes growth. They debate how muscle swelling and transient pump can confound hypertrophy measurements. They unpack sampling variance, study limitations, and why small studies sometimes give mixed results. They also compare full range-of-motion training to partials and practical implications for training choices.
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PRIME Study Praised For MRI And Muscle Selection
- Eric Helms praises Jeremy Ethier's PRIME study for using MRI and varied muscles like rear delts, pecs, glutes, and biceps.
- He notes the study found equivalent hypertrophy between length-biased conditions and highlights good internal validity.
Target Tension, Not Muscle Labels
- Don’t overgeneralize muscle-specific claims; consider anatomy, joint count, and who can actually reach longer sarcomere lengths.
- Aim to maximize tension at longer relative lengths when practically achievable, rather than assuming a tissue-level exception.
Most Small-Effect Studies Will Be Null
- In modeled 10×10 trials with a true small effect (~d=0.2), ~90% of individual studies will be null and ~10% positive by chance.
- Correlation and sample size heavily influence study-level variability.
