PURPOSE This study aimed to evaluate whether motor-respiratory coupling exists in rhythmic isometric handgrip exercises and its effect on endurance performance. In addition, the mechanism underlying observed effects was to be investigated if higher motor-respiratory coupling rate could enhance endurance performance. METHODS Eleven subjects completed three rhythmic isometric handgrip trials to task failure in a randomized manner. After one pretraining session to determine personal grip frequency, one trial was performed without respiration requirement (CON), and two trials were performed with inspiration-motor coupling (IMC) or expiration-motor coupling. Changes in maximal voluntary contraction (MVC) and EMG were used to measure neuromuscular fatigue. Force data during test were used to assess exercise intensity. Another 10 subjects completed electrical stimulation-induced finger flexion and extension during normal inspiration, normal expiration, fast inspiration, fast expiration, and breath holding. Force changes of different breathing conditions were compared. RESULTS Normalized exercise time to exhaustion was significantly longer in IMC (1.27 ± 0.23) compared with expiration-motor coupling (0.82 ± 0.18) and CON (0.91 ± 0.18, P < 0.001). ΔMVC, grip frequency, force, and EMG indices were not different among conditions (all P > 0.05). Electrical stimulation-induced finger extensor force was significant higher during fast inspiration (1.11 ± 0.09) than normal respiration (1.00 ± 0.05) and fast expiration (0.94 ± 0.08, P < 0.05). CONCLUSIONS IMC is an effective way to improve endurance performance of rhythmic handgrip exercise. This is likely due to a reduction in the energy consumption of motion control, as evidenced by similar peripheral fatigue in different conditions and modulation of corticospinal excitability by respiration.

中文翻译：

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运动呼吸耦合可提高节奏等长握力运动期间的耐力表现。


目的本研究旨在评估有节奏的等长握力练习中是否存在运动呼吸耦合及其对耐力表现的影响。此外，如果较高的运动-呼吸耦合率可以增强耐力表现，则需要研究观察到的影响的机制。方法 11 名受试者以随机方式完成了 3 项有节奏的等长握力试验，直至任务失败。经过一次预训练以确定个人握力频率后，进行了一项无呼吸要求 (CON) 的试验，并进行了两次吸气-运动耦合 (IMC) 或呼气-运动耦合的试验。最大随意收缩（MVC）和肌电图的变化用于测量神经肌肉疲劳。测试期间的力数据用于评估运动强度。另外10名受试者在正常吸气、正常呼气、快速吸气、快速呼气和屏气期间完成了电刺激​​引起的手指弯曲和伸展。比较不同呼吸条件下的力变化。结果 与呼气运动耦合组 (0.82 ± 0.18) 和 CON (0.91 ± 0.18，P < 0.001) 相比，IMC 组的标准化运动至力竭时间 (1.27 ± 0.23) 显着更长。 ΔMVC、握力频率、力量和 EMG 指数在不同条件下没有差异（所有 P > 0.05）。电刺激引起的手指伸肌力在快速吸气期间（1.11±0.09）显着高于正常呼吸（1.00±0.05）和快速呼气（0.94±0.08，P < 0.05）。结论 IMC 是提高节奏性握力训练耐力表现的有效方法。 这可能是由于运动控制的能量消耗减少，不同条件下类似的外周疲劳以及呼吸对皮质脊髓兴奋性的调节证明了这一点。