Norberto Matheus Silva, de Arruda Tarine Botta, Papoti Marcelo
Postgraduate Program in Health Sciences Applied to the Locomotor System, Ribeirão Preto Medical School, University of São Paulo, Ribeirão Preto, Brazil.
School of Physical Education and Sport of Ribeirão Preto, University of São Paulo, Ribeirão Preto, Brazil.
Front Physiol. 2020 Sep 23;11:553296. doi: 10.3389/fphys.2020.553296. eCollection 2020.
Neuromuscular fatigue evaluation is widely performed on different muscles through the conventional protocol using maximum voluntary contraction (MVC) with electrical stimuli in the analyzed muscle. In an attempt to use this protocol on elbow extensor musculature, previous studies and pilot studies showed co-contraction effects from antagonist musculature during muscular stimulations. The aim of this study was to propose a new neuromuscular fatigue protocol evaluation on elbow extensor musculature. Twenty participants preformed exercises to induce central (CenFat) and peripheral fatigue (PerFat). Neuromuscular fatigue was evaluated on knee extensor muscles by a conventional protocol that provides Twitch Superimposed (TS) and Twitch Potentiated (TP), central and peripheral parameters respectively. For elbow extensor muscles, the protocol used sustained submaximal contraction at 10, 20, 30, 40, and 50% of MVC. The neuromuscular fatigue in upper limbs was identified by Twitch Potentiated (TP) and multiple Twitch Superimposed (TS) parameters. Using the relationship between MVC (%) and evoked force, the proposed protocol used several TS to provide slope, y-intercept and . It is proposed that slope, , and y-intercept change may indicate peripheral fatigue and the identified relationship between y-intercept and may indicate central fatigue or both peripheral and central fatigue. The results were compared using the non-parametric analyzes of Friedmann and Wilcoxon and their possible correlations were verified by the Spearmann test (significance level set at < 0.05). After PerFat a decrease in TP (57.1%, < 0.001) was found but not in any TS, indicating only peripheral fatigue in upper limbs. After CenFat a decrease in TP (21.4%, : 0.008) and TP (20.9%, < 0.001) were found but not in TS, indicating peripheral fatigue in upper and lower limbs but not central fatigue. A non-significant increase of 15.3% after CenFat and a statistical reduction (80.1%, : 0.001) after PerFat were found by slope. Despite showing differences after both exercises ( < 0.05), it showed a recovery behavior after CenFat (: 0.016). Although PerFat provided only peripheral fatigue, CenFat did not provide central fatigue. Considering the procedural limitations of CenFat, parameters resulting from the proposed protocol are sensitive to neuromuscular alteration, however, further studies are required.
神经肌肉疲劳评估通过常规方案在不同肌肉上广泛进行，该方案使用最大自主收缩（MVC）并在被分析肌肉中施加电刺激。为了在肘伸肌组织上应用此方案，先前的研究和初步研究表明，在肌肉刺激过程中拮抗肌组织存在共同收缩效应。本研究的目的是提出一种针对肘伸肌组织的新的神经肌肉疲劳方案评估方法。20名参与者进行了诱导中枢（CenFat）和外周疲劳（PerFat）的运动。通过一种常规方案对膝伸肌进行神经肌肉疲劳评估，该方案分别提供叠加抽搐（TS）和增强抽搐（TP），即中枢和外周参数。对于肘伸肌，该方案采用在MVC的10%、20%、30%、40%和50%下进行持续次最大收缩。上肢的神经肌肉疲劳通过增强抽搐（TP）和多次叠加抽搐（TS）参数来识别。利用MVC（%）与诱发力之间的关系，所提出的方案使用多个TS来提供斜率、y轴截距和 。提出斜率、 和y轴截距的变化可能表明外周疲劳，并且所确定的y轴截距与 之间的关系可能表明中枢疲劳或外周和中枢疲劳。使用Friedmann和Wilcoxon的非参数分析对结果进行比较，并通过Spearman检验验证其可能的相关性（显著性水平设定为 < 0.05）。在PerFat后，发现TP降低（57.1%，< 0.001），但任何TS均未降低，表明上肢仅存在外周疲劳。在CenFat后，发现TP降低（21.4%，: 0.008）和TP降低（20.9%，< 0.001），但TS未降低，表明上肢和下肢存在外周疲劳但不存在中枢疲劳。通过斜率发现，CenFat后有15.3%的非显著性增加，PerFat后有统计学上的降低（80.1%，: 0.001）。尽管 在两次运动后均显示出差异（< 0.05），但在CenFat后显示出恢复行为（: 0.016）。虽然PerFat仅导致外周疲劳，但CenFat并未导致中枢疲劳。考虑到CenFat的程序局限性，所提出方案产生的参数对神经肌肉改变敏感，然而，还需要进一步研究。
