School of Human Kinetics and Recreation, Memorial University of Newfoundland, St. John's Newfoundland and Labrador (NL), Canada.
Faculty of Physical Education & Sport Sciences, University of Tehran, Tehran, Iran.
J Sports Sci Med. 2022 Jun 1;21(2):214-223. doi: 10.52082/jssm.2022.214. eCollection 2022 Jun.
The occurrence and mechanisms underlying non-local or crossover muscle fatigue is an ongoing issue. This study aimed to investigate crossover fatigue of the plantar flexor muscles. Sixteen recreationally active males (n = 6) and females (n = 10) visited the laboratory for four sessions and performed a single 5-s pre-test maximal voluntary isometric contraction (MVIC) with each plantar flexors muscle. Thereafter, the fatigue intervention involved two 100-s MVICs (60-s recovery) with their dominant plantar flexors or rested for 260-s (control). Subsequently, in two separate sessions, Hoffman reflexes (H-reflex) were evoked in the non-dominant, non-exercised, leg before and following the dominant leg fatigue or control intervention (Fatigue-Reflex and Control-Reflex conditions). MVIC forces and volitional (V)-waves were monitored in the non-dominant leg in the other two sessions (Fatigue-MVIC and Control-MVIC) before and after the intervention (fatigue or control) as well as during 12 repeated MVICs and immediately thereafter. Despite the force reduction in the dominant leg (42.4%, = 0.002), no crossover force deficit with single (F = 0.02, = 0.88, = 0.003) or repeated (F = 0.006, ) MVIC testing were observed. The H-reflex did not change after the fatigue (F = 0.51; = 0.49; 0.06) or repeated MVICs (F = 0.27; = 0.61; 0.03). There were also no crossover effects of fatigue on the V-wave with single (F = 3.71, ) or repeated MVICs (F = 1.45, ). Crossover fatigue was not evident with the plantar flexors nor any significant changes in H-reflex and V-waves in the soleus muscle. This finding suggests that crossover fatigue may not necessarily occur in slow-twitch predominant muscle groups.
非局部或交叉肌肉疲劳的发生和机制是一个持续存在的问题。本研究旨在探讨足底屈肌的交叉疲劳。16 名有运动习惯的男性（n=6）和女性（n=10）分 4 次到实验室进行测试，每次测试均对双侧足底屈肌进行 5 秒最大自主等长收缩（MVIC）预测试。随后，疲劳干预包括两次 100 秒的 MVIC（60 秒恢复期），分别用优势侧和非优势侧足底屈肌进行，或者休息 260 秒（对照组）。接着，在另外两个独立的测试中，在优势侧疲劳或对照组干预（疲劳反射和对照组反射条件）前后，分别在非优势、未运动的腿上诱发非优势侧、未疲劳腿的 Hoffmann 反射（H-反射）。在其他两个测试中，在干预（疲劳或对照组）前后以及在 12 次重复 MVIC 测试期间和之后，在非优势腿上监测 MVIC 力量和随意（V）波。尽管优势腿的力量下降（42.4%， = 0.002），但在单次（F = 0.02， = 0.88， = 0.003）或重复（F = 0.006，）MVIC 测试中并未观察到交叉力量缺陷。疲劳后 H-反射没有变化（F = 0.51； = 0.49； 0.06）或重复 MVICs（F = 0.27； = 0.61； 0.03）。疲劳也没有对 V 波产生交叉效应，无论是单次（F = 3.71，）还是重复 MVICs（F = 1.45，）。在足底屈肌中，没有明显的交叉疲劳，也没有在比目鱼肌中观察到 H-反射和 V-波的显著变化。这一发现表明，在慢肌纤维占主导地位的肌肉群中，交叉疲劳可能不一定会发生。
