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Differential motor unit firing rate and hypertrophic adaptations of the vastus lateralis despite similar strength increases following high-load versus combined high- and low-load resistance training interventions.

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Τίτλος: Differential motor unit firing rate and hypertrophic adaptations of the vastus lateralis despite similar strength increases following high-load versus combined high- and low-load resistance training interventions.
Συγγραφείς: Olmos AA; Department of Molecular Biology and Chemistry, Christopher Newport University, Newport News, VA, 23606, US., Lawson DJ; Fitomics, Alabaster, AL, 36849, US., Sontag SA; School of Kinesiology, Louisiana State University, Baton Rouge, LA, 70803, US., Richardson LD; Applied Neuromuscular Physiology Laboratory, Department of Health and Human Performance, Oklahoma State University, 191 CRC, Stillwater, OK, 47074, US., Roth BL; Applied Neuromuscular Physiology Laboratory, Department of Health and Human Performance, Oklahoma State University, 191 CRC, Stillwater, OK, 47074, US., Jeon S; Department of Health and Human Performance, Northwestern State University, Natchitoches, LA, 71497, US., Redinger AL; Neuromuscular Research Laboratory/Warrior Human Performance Research Center, University of Pittsburgh, Pittsburgh, PA, 15203, US., Gamache SM; Department of Molecular Biology and Chemistry, Christopher Newport University, Newport News, VA, 23606, US., Trevino MA; Applied Neuromuscular Physiology Laboratory, Department of Health and Human Performance, Oklahoma State University, 191 CRC, Stillwater, OK, 47074, US. michael.a.trevino@okstate.edu.
Πηγή: Experimental brain research [Exp Brain Res] 2026 Jun 21; Vol. 244 (7). Date of Electronic Publication: 2026 Jun 21.
Τύπος έκδοσης: Journal Article
Γλώσσα: English
Στοιχεία περιοδικού: Publisher: Springer Verlag Country of Publication: Germany NLM ID: 0043312 Publication Model: Electronic Cited Medium: Internet ISSN: 1432-1106 (Electronic) Linking ISSN: 00144819 NLM ISO Abbreviation: Exp Brain Res Subsets: MEDLINE
Imprint Name(s): Original Publication: Berlin : Springer Verlag
Ιατρικοί όροι (MeSH): Resistance Training*/methods , Adaptation, Physiological*/physiology , Quadriceps Muscle*/physiology , Muscle Strength*/physiology , Action Potentials*/physiology , Recruitment, Neurophysiological*/physiology , Motor Neurons*/physiology, Isometric Contraction/physiology ; Humans ; Male ; Electromyography ; Young Adult ; Adult
Περίληψη: While the role of resistance training-induced muscle hypertrophy on early strength gains is still debated, it is unclear whether the specificity of training, such as high-load (H) training for increasing strength, results in different motor unit (MU) adaptations than combined high- and low-load (H + L) training for increasing strength and hypertrophy. Therefore, this study examined the effects of six weeks of either H- or H + L-training on leg press 1-repetition maximum (1-RM), isometric knee extensor strength via maximal voluntary contraction (MVC), and muscle cross-sectional area (mCSA) and MU behavior of the vastus lateralis (VL) in untrained males that were pseudorandomized into a H (n = 18), H + L (n = 17), or a control group (n = 11). Surface electromyographic (sEMG) signals for a 40% MVC were recorded from the VL and decomposed for analysis of MU: recruitment thresholds (RTs), action potential amplitudes (MUAPAMPs), and mean firing rates (MFRs). Normalized EMG amplitude (N-EMGRMS) at 40% MVC was also calculated. Despite a 21% increase in mCSA for H + L compared to 4% for H, both training groups had similar increases for 1-RM and MVC. Additionally, H + L exhibited hypertrophied muscle fibers for MUs with RTs ≥ 20% MVC, decreased MFR of those MUs, and lower N-EMGRMS at 40% MVC, whereas H increased MFRs of the lower-threshold MUs with no change in MU size or N-EMGRMS. The findings of this study provide support that early changes in MU behavior are sensitive to specificity of training and/or changes in muscle morphology, whereas early strength gains are not necessarily driven by increases in mCSA.
(© 2026. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.)
Competing Interests: Declarations. Competing intersts: The authors declare no conflicts of interest, financial or otherwise.
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Contributed Indexing: Keywords: Motor unit; Muscle hypertrophy; Resistance training; Vastus lateralis
Entry Date(s): Date Created: 20260621 Date Completed: 20260621 Latest Revision: 20260701
Update Code: 20260701
DOI: 10.1007/s00221-026-07334-6
PMID: 42323749
Βάση Δεδομένων: MEDLINE
Περιγραφή
ISSN:1432-1106
DOI:10.1007/s00221-026-07334-6