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Updated: Jun 13, 2025
Isolation, Culture, Characterization, and Differentiation of Human Muscle Progenitor Cells from the Skeletal Muscle Biopsy Procedure
Published on: August 23, 2019
Individual muscle hypertrophy response is affected by the overload progression model and is associated with changes
Maíra C Scarpelli1,2, João G A Bergamasco1,2, Joshua S Godwin2
1MUSCULAB - Laboratory of Neuromuscular Adaptations to Resistance Training, Department of Physical Education, Federal University of São Carlos - UFSCar, Rod. Washington Luiz, km 235 - SP 310, São Carlos, SP, CEP 13565-905, Brazil.
Purpose:
We aimed to compare individual hypertrophic responses to resistance training in which overload progressed either by adjusting the load (LOADProg) or by increasing the number of repetitions (REPSProg). Furthermore, we investigated whether greater responsiveness to one protocol was associated with chronic changes in myonuclei and satellite cells, proteolysis and extracellular matrix (ECM) remodeling biomarkers.
Methods:
Thirty-seven untrained participants had their legs randomized into LOADProg and REPSProg and underwent 10 weeks of training. Muscle cross-sectional area (mCSA) ultrasound and muscle biopsies were performed pre- and post-training. Based on mCSA changes between protocols, we applied a criterion of 2 typical errors (5.7%) to create 4 clusters.
Results:
Twelve participants (~ 34%) showed greater mCSA increases after REPSProg (14.2 ± 7.6%) than LOADProg (3.4 ± 8.7%, p = 0.004). Seven participants (~ 19%) responded better to LOADProg (21.5 ± 7.5% vs. 12 ± 7.5%, p = 0.041). Thirteen participants (~ 35%) showed no differences between protocols (p = 0.852). Five participants were nonresponders (mCSA changes smaller than the 5.7% threshold) for both protocols. There were no significant differences (p > 0.05) in myonuclear content, proteolysis, or ECM remodeling markers within any of the clusters. However, for those who responded better to REPSProg, this protocol promoted greater satellite cell changes (108.6 ± 77.0%) than LOADProg (48.9 ± 63.1%, p = 0.015).
Conclusion:
Our findings suggest that overload progression models may influence individual responsiveness to RT-induced muscle hypertrophy. Additionally, progression through increased repetitions was associated with a chronic addition of satellite cells. However, responsiveness was not explained by chronic changes in myonuclei, proteolysis or ECM remodeling biomarkers.
Trial Registration:
This study is registered in the Brazilian Registry of Clinical Trials (RBR-57v9mrb).
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