About this Research Topic
Neuromuscular fatigue is commonly defined as a reduction in maximum force-generating capacity of a muscle induced by physical exercise. Two main aspects are generally involved in this phenomenon: (i) a central component that includes all the events spanning from the motor cortex activation, motor drive passage through supraspinal and spinal pathways toward the neuromuscular junction; and (ii) a peripheral component that encloses all the electrochemical and mechanical factors occurring downstream the neuromuscular junction until the force transmission at the tendon insertion point. Although a consistent body of literature focused on neuromuscular fatigue, there is still limited information on the exact mechanisms underlying the reduction in the force-generating capacity, due to the different approaches used to induce fatigue and points of observation where force generation and transmission can be affected.
The physiology of neuromuscular fatigue has been mainly investigated by focusing only on single aspects of fatigue, providing only partial (albeit deep) explanations of the mechanisms underlying such a multifaceted phenomenon. More recently, the progress in technological and methodological means, such as the transcranial magnetic stimulation, the functional magnetic resonance, the magnetic resonance spectroscopy, the shear wave elastography, the accelerometers and the high-density surface electromyography has expanded our knowledge in the contribution of the neural, electrochemical and mechanical factors to force output impairment during and after a fatiguing task. These new technologies/approaches permitted to study the phenomenon of neuromuscular fatigue under a multilevel point of view. As examples, (i) the combined use of transcranial magnetic stimulation, nerve stimulation and surface electromyography allows to investigate the effect of fatigue at several sites of the cortico-spinal pathway, (ii) the use of high-density surface electromyography and the analysis of the obtained signal permits to estimate the contribution of the synergistic muscles included in a given movement in contrasting fatigue, and (iii) the combined analysis of the surface electromyogram, mechanomyogram (or high frame rate ultrasound) and force signals during a fatiguing contraction allows to evaluate the effect of fatigue on the electrochemical events linked to the excitation-contraction coupling and the mechanical events linked to the force transfer at the tendon insertion point. Notably, only a limited number of studies used an experimental set up for inducing fatigue during and after real-life sports performance (e.g. endurance runs or team sports matches or repeated individual competitions) or daily activities (e.g. night-shift workers). The present research topic would aim to shed a light on the mechanisms underpinning neuromuscular fatigue by combining different technologies/methodologies and using approaches reflecting possible real-life contexts.
The aim to this Research Topic will be to include original articles that assess the phenomenon of neuromuscular fatigue with a translational approach, trying to define a multilevel perspective of the topic. Moreover, studies adopting designs to study the occurrence of neuromuscular fatigue in real-life sports performance or daily activities contexts are welcome. Lastly, literature reviews and metanalysis including studies that have investigated the neuromuscular fatigue under a multilevel point of view and/or in real-life contexts will be also considered.
Keywords: Skeletal muscle fatigue, new technologies, real-life sport performance, daily activities
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