20.500.12556/DiRROS-22244 Twenty-one days of bed rest alter motor unit properties and neuromuscular junction transmission in young adults Previous studies showed that properties of higher‐threshold motor units (MUs) and neuromuscular junction (NMJ) function are preserved during short‐term disuse. This study aimed to test how a longer disuse period affects MU properties, NMJ transmission, and NMJ morphology remodeling. Nine young healthy males (age: 18‐29 years) underwent 21 days of horizontal bed rest. Pre‐ (BR0) and post‐bed rest (BR21), quadriceps maximal voluntary contraction (MVC), and size were assessed. We combined intramuscular electromyography (iEMG) and high‐density surface electromyography (HDsEMG) recordings on the vastus lateralis to assess MU properties at 25% and 50% of MVC. Muscle biopsies and blood samples were also collected. Quadriceps MVC and size decreased at BR21. We found alterations in MU properties at both contraction intensities, including reduced discharge rate, MU potential area changes, and increased complexity. NMJ transmission was found to be reduced at BR21 at 25% MVC. This functional NMJ impairment was biochemically corroborated by an increase in serum C‐terminal agrin fragment concentration, a biomarker of NMJ instability. In addition, a direct assessment of NMJ morphology revealed the presence of some denervated NMJs exclusively at BR21. In conclusion, 21‐day bed rest altered MU properties across different contraction intensities and impaired NMJ transmission with initial signs of remodeling/denervation. Disuse duration appears to be a critical factor, as previous shorter studies failed to detect some of these changes. We believe these findings are clinically relevant for disuse after trauma, surgery, or illness, and may support the development of effective countermeasures. disuse unloading physical inactivity electrophysiology electromyography neuporaba razbremenitev fizična neaktivnost elektrofiziologija elektromiografija true false true Angleški jezik Slovenski jezik © 2025 The Authors Neznano 2025-05-13 12:52:46 2025-05-13 12:52:46 2025-10-24 03:50:54 0000-00-00 00:00:00 2025 0 0 Nasl. z nasl. zaslona; Opis vira z dne 13. 5. 2025; Soavtorji: Miloš Kalc, Evgeniia S. Motanova, Martino V. Franchi, Daniel Stashuk, Nina Murks, Giacomo Valli, Samuele Negro, Tomaž Prašnikar, Mladen Gasparini, Giovanni Martino, Giuseppe De Vito, Aleš Holobar, Boštjan Simunič3 , Rado Pišot, and Marco V. Narici; str. 1-37 iss. Vol. 2025 0000-00-00 Zaloznikova Objavljeno NiDoloceno 0000-00-00 0000-00-00 2025-01-01 612.741 1522-1601 10.1152/japplphysiol.00178.2025 235704579 25_05_13_101_Kalc_235704579.pdf 25_05_13_101_Kalc_235704579.pdf 1 B4D32D6FF1AC1B0C5F077E0F13E5E1C0 316a7ccfe5754ba9263f1557133a407d3aa88cf9a49e43ce8a118f12b8ebee38 af49b59c-2fe8-11f0-963a-001a4af901a5 https://dirros.openscience.si/Dokument.php?lang=slv&id=32214 https://journals.physiology.org/doi/epdf/10.1152/japplphysiol.00178.2025 1 69d954c3-2fe8-11f0-963a-001a4af901a5 https://dirros.openscience.si/Dokument.php?lang=slv&id=32213 Znanstveno-raziskovalno središče Koper / Centro di Ricerche Scientifiche Capodistria 0 0 0