Research

Mixed

Muscle typology (determined by muscle carnosine levels) does not explain inter-individual variability in resistance training-induced increases in muscle volume, maximal dynamic strength, or fiber cross-sectional area when training is performed to failure at 60% 1RM.

If you are new to resistance training, your muscle fiber type (whether you are naturally 'fast' or 'slow') does not determine how much muscle or strength you will gain. As long as you train to failure with a moderate load (around 60% of your max), you will see similar improvements regardless of your genetics. Focus on consistency and effort rather than trying to tailor your program to your fiber type.

GoodRefutesHIGH confidence
The training response for total muscle volume (+3 to +14%), fiber size (-19 to +22%) and strength (+17 to +47%) showed considerable inter-individual variability, but these could not be attributed to differences in muscle typology.
Kim Van Vossel et al. · The Journal of Physiology · 2023

Why this rating

Randomized controlled trial with a within-subject design, objective MRI and biopsy measures, and clear exclusion criteria.

Source

Can muscle typology explain the inter‐individual variability in resistance training adaptations?

Kim Van Vossel et al. · The Journal of Physiology · 2023

DOI 10.1113/jp284442

rct · n=50Cited 26×
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DOI resolved against Crossref · corpus check 2026-06-10

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