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Effects of low-load resistance training with blood flow restriction on muscle fiber myofibrillar and extracellular area
Roberts, Michael D
Roberts, Michael D
Abstract
Blood flow restriction applied during low-load resistance training (LL-BFR) induces a similar increase in the cross-sectional area of muscle fibers (fCSA) compared to traditional high-load resistance training (HL-RT). However, it is unclear whether LL-BFR leads to differential changes in myofibrillar spacing in muscle fibers and/or extracellular area compared to HL-RT. Therefore, this study aimed to investigate whether the hypertrophy of type I and II fibers induced by LL-BFR or HL-RT is accompanied by differential changes in myofibrillar and non-myofibrillar areas. In addition, we examined if extracellular spacing was differentially affected between these two training protocols. Twenty recreationally active participants were assigned to LL-BFR or HL-RT groups and underwent a 6-week training program. Muscle biopsies were taken before and after the training period. The fCSA of type I and II fibers, the area occupied by myofibrillar and non-myofibrillar components, and extracellular spacing were analyzed using immunohistochemistry techniques. Despite the significant increase in type II and mean (type I + II) fCSA ( < 0.05), there were no significant changes in the proportionality of the myofibrillar and non-myofibrillar areas [∼86% and ∼14%, respectively ( > 0.05)], indicating that initial adaptations to LL-BFR are primarily characterized by conventional hypertrophy rather than disproportionate non-myofibrillar expansion. Additionally, extracellular spacing was not significantly altered between protocols. In summary, our study reveals that LL-BFR, like HL-RT, induces skeletal muscle hypertrophy with proportional changes in the areas occupied by myofibrillar, non-myofibrillar, and extracellular components.
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2024-02-20
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Frontiers
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fphys-15-1368646.pdf
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vascular occlusion
Citation
Libardi CA, Godwin JS, Reece TM, Ugrinowitsch C, Herda TJ, Roberts MD. Effects of low-load resistance training with blood flow restriction on muscle fiber myofibrillar and extracellular area. Front Physiol. 2024 Feb 20;15:1368646. doi: 10.3389/fphys.2024.1368646. PMID: 38444764; PMCID: PMC10912282