The Study
Differential changes in muscle architecture and neuromuscular fatigability induced by isometric resistance training at short and long muscle-tendon unit lengths.
This study looked at how two different ways of doing leg exercises might change your muscles and how tired they get. It found that one way made your muscles look a little different and that change was kind of linked to how long you could keep exercising — but it’s not clear if the exercise actually caused the change.
Analysis score
Maximum 90 for a randomized controlled trial.
Where the score came from
People did leg exercises holding their muscle stretched out vs. bunched up for 8 weeks. One way made muscle fibers longer; the other made them thicker and angled. Neither way made people much less tired, but the changes in muscle shape were linked to how tired they felt.
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 546 / 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 changes in muscle shape were clear, but the effect on feeling less tired was too small to be sure it mattered in real life.
- 2Fascicle length increased by ~4% with long-length training.
- 3Pennation angle increased by ~6% with short-length training.
- 4Fatigue resistance improved by ~20% (short) and ~51% (long), but not significantly (P = 0.081).
- 5Correlations: r = 0.739 (positive) and r = -0.568 (negative).
Score breakdown, methodology, conflicts of interest, evidence analysis & raw study data
Publication
Journal
Journal of applied physiology
Year
2020
Authors
R. Akagi, Avery Hinks, Geoffrey A. Power
Related Content
Claims (6)
Doing 8 weeks of strength training with your muscle either stretched or bunched up doesn’t make you much better at resisting fatigue — the improvement is very small and not clearly real.
Doing strength exercises with your muscle stretched out for 8 weeks can make the muscle fibers longer, but doing them with your muscle bunched up doesn’t change their length.
Doing strength exercises with your muscle bunched up for 8 weeks can make the muscle fibers angle more sharply, which might help them generate more force.
When people train with their muscles bunched up, the more their muscle fibers angle upward, the longer they can keep pushing hard before getting tired.
When people train with their muscles stretched out, the longer their muscle fibers get, the more quickly they tire out during repeated efforts.
Isometric contractions performed at longer muscle lengths produce greater muscle hypertrophy than isometric contractions performed at shorter muscle lengths.
Not medical advice. For informational purposes only. Always consult a qualified healthcare professional before making health decisions.