INSERM UMR1093-CAPS, Université de Bourgogne, UFR des Sciences du Sport, Dijon, France.
Geriatrics Internal Medicine Department, University Hospital of Dijon Bourgogne, Dijon, France.
J Appl Physiol (1985). 2023 May 1;134(5):1093-1104. doi: 10.1152/japplphysiol.00601.2022. Epub 2023 Mar 17.
The purpose of this study is to investigate if a continuous muscle contraction (CON) is more fatiguing than an intermittent exercise (INT) performed until task failure. To get a more comprehensive picture of neuromuscular fatigability, in addition to the commonly used maximal voluntary contraction (MVC), we assessed the maximal torque sustainability (i.e., the ability to maintain a high level of torque for 1 min). Fourteen subjects performed a plantar flexors MVC of 1-min duration (MVC) before and after CON or INT contractions at 40% MVC until task failure. Despite a greater torque-time integral for the INT task, a similar MVC reduction was found after both exercises. On the contrary, a greater torque loss during the MVC was observed after the CON exercise and it was positively correlated to the mean exercise torque. These results reveal that, for exercises performed until exhaustion, the contraction pattern (i.e., CON vs. INT) affects the ability to maintain a high level of torque, but does not influence the maximal torque production capacity. Thus, we demonstrate that maximal torque production and sustainability are two distinct and complementary characteristics of neuromuscular fatigability. Consequently, when considering both capacities, it results that, an exhausting CON contraction is more fatiguing than an exhausting INT effort. This highlights the importance of simultaneously evaluating both capacities when exploring neuromuscular fatigability. This study provides new information about the influence of the contraction pattern (i.e., continuous and intermittent) on the development of neuromuscular fatigability when exercise is performed until exhaustion. Maximal torque production is similarly reduced by both exercises, whereas maximal torque sustainability is impaired only after the continuous exercise. To evaluate neuromuscular fatigability, we then recommend using a sustained maximal voluntary contraction since this measure allows to concurrently collect information on complementary aspects of neuromuscular fatigability.
本研究旨在探究连续肌肉收缩（CON）是否比间歇运动（INT）更易引起疲劳，而间歇运动则一直持续到任务失败。为了更全面地了解神经肌肉疲劳性，除了常用的最大自主收缩（MVC）外，我们还评估了最大扭矩维持能力（即保持高扭矩水平 1 分钟的能力）。14 名受试者在 CON 或 INT 收缩前和后进行了 1 分钟的足底屈肌 MVC（MVC），收缩强度为 40% MVC，直到任务失败。尽管 INT 任务的扭矩时间积分更大，但两种运动后 MVC 减少幅度相似。相反，CON 运动后观察到 MVC 期间的扭矩损失更大，并且与平均运动扭矩呈正相关。这些结果表明，对于直至疲劳的运动，收缩模式（即 CON 与 INT）会影响维持高扭矩水平的能力，但不会影响最大扭矩产生能力。因此，我们证明了最大扭矩产生和维持是神经肌肉疲劳性的两个不同且互补的特征。因此，当考虑这两种能力时，令人筋疲力尽的 CON 收缩比令人筋疲力尽的 INT 运动更疲劳。这强调了在探索神经肌肉疲劳性时同时评估这两种能力的重要性。本研究提供了有关收缩模式（即连续和间歇）对疲劳运动时神经肌肉疲劳性发展影响的新信息。两种运动都会使最大扭矩产生量减少，但只有连续运动后才会损害最大扭矩维持能力。为了评估神经肌肉疲劳性，我们建议使用持续的最大自主收缩，因为这种测量方法可以同时收集神经肌肉疲劳性互补方面的信息。
