| Title: | Inter-person differences in isometric coactivations of triceps surae and tibialis anterior decrease in young, but not in older adults after 14 days of bed rest |
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| Authors: | ID Divjak, Matjaž (Author)
ID Sedej, Gašper (Author)
ID Murks, Nina (Author)
ID Gerževič, Mitja (Author)
ID Marušič, Uroš (Author)
ID Pišot, Rado (Author)
ID Šimunič, Boštjan (Author)
ID Holobar, Aleš (Author) |
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| Files: |  URL - Source URL, visit https://doi.org/10.3389/fphys.2021.809243
 PDF - Presentation file, download (4,31 MB)
MD5: D08A3FAF45654AA8D615EF2664B816BF
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| Language: | English |
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| Typology: | 1.01 - Original Scientific Article |
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| Organization: |  ZRS Koper - Science and Research Centre Koper
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| Abstract: | We examined activation patterns of the gastrocnemius medialis (GM), gastrocnemius lateralis (GL), soleus (SO), and tibialis anterior (TA) muscles in eight older (58.4 ± 3.3 years) and seven young (23.1 ± 2.9 years) participants, before and after 14 days of horizontal bed rest. Visual feedback on the exerted muscle torque was provided to the participants. The discharge patterns of individual motor units (MUs) were studied in three repetitions of isometric plantar flexion at 30 and 60% of Maximum Voluntary Contraction (MVC), before, and 1 day after the 14-day bed rest, respectively. In the GL and GM muscles, the older participants demonstrated higher MU discharge rates than the young, regardless of the contraction level, both before and after the bed rest. In the TA and SO muscles, the differences between the older and young participants were less consistent. Detailed analysis revealed person-specific changes in the MU discharge rates after the bed rest. To quantify the coactivation patterns we calculated the correlation coefficients between the cumulative spike trains of identified MUs from each muscle, and measured the root mean square difference of the correlation coefficients between the trials of the same session (intra-session variability) and between different sessions (inter-session variability) in each participant (intra-person comparison) and across participants (inter-person comparison). In the intra-person comparison, the inter-session variability was higher than the intra-session variability, either before or after the bed rest. At 60% MVC torque, the young demonstrated higher inter-person variability of coactivation than the older participants, but this variability decreased significantly after the bed rest. In older participants, inter-person variability was consistently lower at 60% than at 30% MVC torque. In young participants, inter-person variability became lower at 60% than at 30% MVC torque only after the bed rest. Precaution is required when analyzing the MU discharge and coactivation patterns, as individual persons demonstrate individual adaptations to aging or bed rest. |
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| Keywords: | high density electromyography, muscle disuse, motor units, discharge rate, aging |
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| Publication status: | Published |
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| Publication version: | Version of Record |
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| Article acceptance date: | 24.12.2021 |
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| Publication date: | 28.01.2022 |
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| Year of publishing: | 2022 |
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| Number of pages: | str. 1-14 |
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| Numbering: | Vol. 12, art. 809243 |
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| PID: | 20.500.12556/DiRROS-15445  |
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| UDC: | 612.74:004.8 |
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| ISSN on article: | 1664-042X |
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| DOI: | 10.3389/fphys.2021.809243 |
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| COBISS.SI-ID: | 95552515 |
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| Copyright: | © 2022 Divjak, Sedej, Murks, Geržević, Marusic, Pišot, Šimunič and
Holobar. |
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| Note: | Nasl. z nasl. zaslona;
Soavtorji: Gašper Sedej, Nina Murks, Mitja Gerževič, Uros Marusic, Rado Pišot, Boštjan Šimunič and Aleš Holobar;
Opis vira z dne 31. 1. 2022;
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| Publication date in DiRROS: | 05.09.2022 |
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| Views: | 1092 |
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| Downloads: | 571 |
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