20.500.12556/DKUM-90160 Motor unit discharge rate modulation during isometric contractions to failure is intensity- and modality-dependent The physiological mechanisms determining the progressive decline in the maximal muscle torque production capacity during isometric contractions to task failure are known to depend on task demands. Task-specificity of the associated adjustments in motor unit discharge rate (MUDR), however, remains unclear. This study examined MUDR adjustments during different submaximal isometric knee extension tasks to failure. Participants performed a sustained and an intermittent task at 20% and 50% of maximal voluntary torque (MVT), respectively (Experiment 1). High-density surface EMG signals were recorded from vastus lateralis (VL) and medialis (VM) and decomposed into individual MU discharge timings, with the identified MUs tracked from recruitment to task failure. MUDR was quantified and normalised to intervals of 10% of contraction time (CT). MUDR of both muscles exhibited distinct modulation patterns in each task. During the 20% MVT sustained task, MUDR decreased until ∼50% CT, after which it gradually returned to baseline. Conversely, during the 50% MVT intermittent task, MUDR remained stable until ∼40–50% CT, after which it started to continually increase until task failure. To explore the effect of contraction intensity on the observed patterns, VL and VM MUDR was quantified during sustained contractions at 30% and 50% MVT (Experiment 2). During the 30% MVT sustained task, MUDR remained stable until ∼80–90% CT in both muscles, after which it continually increased until task failure. During the 50% MVT sustained task the increase in MUDR occurred earlier, after ∼70–80% CT. Our results suggest that adjustments in MUDR during submaximal isometric contractions to failure are contraction modality- and intensity-dependent. muscle contractions high-density EMG signals electromyiograms elektromiogrami signali EMG kontrakcija mišic true false true The Physiological Society, Wiley Angleški jezik Slovenski jezik https://physoc.onlinelibrary.wiley.com/journal/14697793 © 2024 The Authors Članek v reviji 2024-08-23 12:39:43 2024-08-23 12:39:44 2026-01-13 08:50:47 0000-00-00 00:00:00 2024 0 0 Str. 2287-2314 iss. 10 Vol. 602 2024 0000-00-00 Zaloznikova Objavljeno NiDoloceno 2023-12-14 2024-03-25 2024-04-13 61:004.8 192788739 10.1113/JP286143 1469-7793 The_Journal_of_Physiology_-_2024_-_Valencic_-_Motor_unit_discharge_rate_modulation_during_isometric_contractions_to_failure.pdf The_Journal_of_Physiology_-_2024_-_Valencic_-_Motor_unit_discharge_rate_modulation_during_isometric_contractions_to_failure.pdf 1 89E25EBBC3D02CD031078552DDA3C59D dffada3d2e41dbf4399a305d5277d8ad3be45cb4d9d207b04d3adb9a5230a50c 64a79e66-613c-11ef-84e9-00155d000105 https://dk.um.si/Dokument.php?lang=slv&id=183186 https://physoc.onlinelibrary.wiley.com/doi/10.1113/JP286143 1 1e68b7de-613c-11ef-84e9-00155d000105 https://dk.um.si/Dokument.php?lang=slv&id=183185 Fakulteta za elektrotehniko, računalništvo in informatiko 0 0 0