The Study
Muscle fiber hypertrophy, hyperplasia, and capillary density in college men after resistance training.
This study shows what happened to 12 college guys' muscles after they did weight training for 12 weeks. It can tell us that muscle size went up, but it can't prove the training was the only reason — it's like saying 'I ate ice cream and then I felt happy,' but we don't know if the ice cream really caused it.
Analysis score
Maximum 44 for a cross-sectional study.
Where the score came from
Men did weight training for 12 weeks. Scientists checked their arm muscles before and after to see how they changed.
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 531 / 100
Quality score
Snapshots of a population at a single point in time, or descriptions of small groups. Can identify correlations and prevalence, but cannot determine cause and effect.
Key takeaways
Summary
Based on the study abstract and findings.
- 1The muscle got stronger and bigger, but it did so by growing existing fibers, not by adding new ones.
- 2Strength went up 25%.
- 3Muscle size went up 12.7%.
- 4Muscle fibers got bigger but didn’t increase in number.
- 5Capillaries per fiber went up, but not per area.
Score breakdown, methodology, conflicts of interest, evidence analysis & raw study data
Publication
Journal
Journal of applied physiology
Year
1996
Authors
G. McCall, W. Byrnes, A. Dickinson, P. Pattany, S. Fleck
Related Content
Claims (6)
When you lift weights, your muscles get bigger not because you're growing new muscle fibers, but because the ones you already have are getting thicker. Scientists don't think you actually create new muscle fibers from training.
Lifting weights for three months makes the muscle fibers in young men's biceps get bigger — both the endurance-type and power-type fibers.
Lifting weights for three months increases the number of tiny blood vessels in arm muscles of young men, and the growth keeps up with how much the muscle fibers get bigger.
If college guys who've lifted weights before do a specific 12-week workout plan—3 times a week, 8 exercises, 3 sets each—they'll get 25% stronger in their arms, based on how much they can lift in one go on a curl machine.
Lifting weights for three months can make the upper arm muscle about 13% bigger in young college guys.
Lifting weights for three months didn’t increase the number of muscle fibers in young guys’ biceps, so their muscles got bigger without adding new fibers.
Not medical advice. For informational purposes only. Always consult a qualified healthcare professional before making health decisions.