Angelidis Angelos, Drzymała-Celichowska Hanna, Kryściak Katarzyna, Vandenboom Rene, Celichowski Jan
Department of Kinesiology, Centre for Bone and Muscle Health, Brock University, 1812 Sir Isaac Brock Way, St. Catharines, ON, L2S 3A1, Canada.
Department of Neurobiology, Poznan University of Physical Education, Poznan, Poland.
Sci Rep. 2025 Jul 2;15(1):23085. doi: 10.1038/s41598-025-07607-0.
During contractile activity, force can be reduced (i.e., fatigue/performance fatigability) or increased (i.e., potentiation) in a stimulation frequency and task-dependent manner, through the parallel action of various potentiating and fatiguing mechanisms. Potentiation and fatigue can be observed concomitantly, with the most characteristic example being increased submaximal force in parallel with maximal tetanic force reduction. The majority of these observations come from isolated whole muscle models, with less data available at the motor unit level. Here, we investigated the coexistence of fatigue and potentiation in rat medial gastrocnemius fast fatigable (i.e., FF) and fast fatigue resistant (i.e., FR) motor units in situ, using a 180-s repetitive isometric contractile protocol including twitches, unfused tetani of different fusion degrees (30 Hz, 40 Hz) and maximal tetanic contractions (150 Hz). Potentiation of twitch and unfused tetanic force was apparent in both motor unit types in parallel with reduced maximal tetanic force. Considerable overlap in potentiation magnitude between FF and FR units was observed, across stimulation frequencies. FF units exhibited potentiation more rapidly compared to FR units.
在收缩活动期间，通过各种增强和疲劳机制的并行作用，力可以以刺激频率和任务依赖的方式降低（即疲劳/性能疲劳性）或增加（即增强）。增强和疲劳可以同时观察到，最典型的例子是次最大力增加，同时最大强直收缩力降低。这些观察结果大多来自分离的整块肌肉模型，在运动单位水平上可用的数据较少。在这里，我们使用180秒的重复性等长收缩方案，包括单收缩、不同融合程度（30Hz、40Hz）的非融合强直收缩和最大强直收缩（150Hz），研究了大鼠内侧腓肠肌快疲劳型（即FF）和快抗疲劳型（即FR）运动单位中疲劳和增强的共存情况。在两种运动单位类型中，单收缩和非融合强直收缩力的增强都很明显，同时最大强直收缩力降低。在不同刺激频率下，观察到FF和FR单位之间的增强幅度有相当大的重叠。与FR单位相比，FF单位表现出更快的增强。
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