Heavy or light: is muscle fiber growth load-specific? A systematic review and meta-regression.
4 affiliations
- 1Faculty of Kinesiology, University of Zagreb, Zagreb, Croatia.
- 2Department of Sports Science and Physical Education, Nord University, Levanger, Norway.
- 3Academy for Personal Training, Fredrikstad, Norway.
- 4Department of Sports Science and Physical Education, Faculty of Education, The Chinese University of Hong Kong, Hong Kong, Hong Kong SAR, China.
Abstract
Introduction
Training load, expressed as a percentage of one-repetition maximum (%1RM), is an important variable in resistance training. Prior studies comparing low- and high-load training on muscle fiber hypertrophy reported conflicting findings, and the load-specific relationship has not been analyzed in a continuous manner. This systematic review and meta-regression explored the relationship between training load and muscle fiber hypertrophy.Methods
A systematic search was conducted in PubMed/MEDLINE, Scopus, and SPORTDiscus databases. Standardized mean changes (SMC) were calculated and analyzed using multilevel meta-regressions with cluster-robust variance estimation, with exploratory sensitivity and interacting moderator analyses. Eight studies involving 195 participants were included.Results
In the fiber-type specific model, pairwise contrast estimates were negative at low loads (20-30% 1RM: -0.147 to -0.088 SMC) and positive at higher loads (60-90% 1RM: 0.089-0.265 SMC). However, the 95% confidence intervals included zero for all pairwise contrasts.Conclusion
The observed model estimates suggested a potential fiber-type specific pattern across loading ranges. However, these findings should be considered preliminary and interpreted with caution given the small number of included studies and wide 95% confidence and prediction intervals, indicating a degree of uncertainty and imprecision.
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BibTeX
@article{varovic2026heavy,
title = {{Heavy or light: is muscle fiber growth load-specific? A systematic review and meta-regression.}},
author = {Dorian Varovic and Stian Larsen and Jozo Grgic},
journal = {Frontiers in physiology},
year = {2026},
month = oct,
doi = {10.3389/fphys.2026.1953601},
url = {https://europepmc.org/article/MED/42903128},
note = {CC BY},
}
RIS
TY - JOUR
TI - Heavy or light: is muscle fiber growth load-specific? A systematic review and meta-regression.
AU - Dorian Varovic
AU - Stian Larsen
AU - Jozo Grgic
PY - 2026
DA - 2026/10/06
JO - Frontiers in physiology
DO - 10.3389/fphys.2026.1953601
UR - https://europepmc.org/article/MED/42903128
AB - Introduction Training load, expressed as a percentage of one-repetition maximum (%1RM), is an important variable in resistance training. Prior studies comparing low- and high-load training on muscle fiber hypertrophy reported conflicting findings, and the load-specific relationship has not been analyzed in a continuous manner. This systematic review and meta-regression explored the relationship between training load and muscle fiber hypertrophy.Methods A systematic search was conducted in PubMed/MEDLINE, Scopus, and SPORTDiscus databases. Standardized mean changes (SMC) were calculated and analyzed using multilevel meta-regressions with cluster-robust variance estimation, with exploratory sensitivity and interacting moderator analyses. Eight studies involving 195 participants were included.Results In the fiber-type specific model, pairwise contrast estimates were negative at low loads (20-30% 1RM: -0.147 to -0.088 SMC) and positive at higher loads (60-90% 1RM: 0.089-0.265 SMC). However, the 95% confidence intervals included zero for all pairwise contrasts.Conclusion The observed model estimates suggested a potential fiber-type specific pattern across loading ranges. However, these findings should be considered preliminary and interpreted with caution given the small number of included studies and wide 95% confidence and prediction intervals, indicating a degree of uncertainty and imprecision.
SN - 1664-042X
ER -