How Lifting Weights Changes Muscles Inside
Myofibril and Mitochondrial Area Changes in Type I and II Fibers Following 10 Weeks of Resistance Training in Previously Untrained Men
Not medical advice. For informational purposes only. Always consult a healthcare professional. Terms
Lifting weights makes muscles bigger and stronger by growing the parts inside muscle cells in different ways.
No biological mechanisms were identified in this study. This may be an epidemiological, observational, or survey-based study that reports associations rather than proposing causal biological pathways.
Systematic Reviews & Meta-Analyses
Max 100Randomized Controlled Trials
Max 90Cohort Studies
Max 72Case-Control Studies
Max 58Cross-Sectional Studies
Max 44Case Reports & Case Series
Max 30Expert Opinion & Narrative Reviews
Max 531 / 72
Evidence Score
Groups of people are followed over time to see who develops an outcome. Strong for identifying risk factors and associations, but cannot prove causation as firmly as RCTs.
Not medical advice. For informational purposes only. Always consult a healthcare professional. Terms
Lifting weights makes muscles bigger and stronger by growing the parts inside muscle cells in different ways.
No biological mechanisms were identified in this study. This may be an epidemiological, observational, or survey-based study that reports associations rather than proposing causal biological pathways.
Systematic Reviews & Meta-Analyses
Max 100Randomized Controlled Trials
Max 90Cohort Studies
Max 72Case-Control Studies
Max 58Cross-Sectional Studies
Max 44Case Reports & Case Series
Max 30Expert Opinion & Narrative Reviews
Max 531 / 72
Evidence Score
Groups of people are followed over time to see who develops an outcome. Strong for identifying risk factors and associations, but cannot prove causation as firmly as RCTs.
Publication
Authors
Ruple BA, Godwin JS, Mesquita PHC, Osburn SC, Sexton CL, Smith MA, Ogletree JC, Goodlett MD, Edison JL, Ferrando AA, Fruge AD, Kavazis AN, Young KC, Roberts MD
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Claims (6)
When scientists measure changes in muscle cells after strength training using two different methods, the results don't match up well - so they should be looked at separately rather than compared directly.
When young guys who haven't lifted weights before do strength training for 10 weeks, their muscle fibers grow in a way that makes them stronger, not just bigger with extra fluid. It's like building real muscle instead of just puffing it up.
When young guys who don't exercise start lifting weights for 10 weeks, the energy-producing parts inside their muscles grow faster than the muscles themselves.
When untrained young men do strength training, a special scan called pQCT can show changes in muscle density that match changes in muscle fiber size, suggesting this scan might help track muscle growth without surgery.
In young men who don't exercise, slow-twitch muscle fibers have more energy-producing parts than fast-twitch fibers to start with, and even after 10 weeks of weight training—which boosts these parts overall—the slow-twitch ones still keep their lead.