Department of Electrical and Electronical Engineering, Universidad Pública de Navarra D.I.E.E., Campus de Arrosadía s/n, 31006, Pamplona, Spain.
Department of Physiology, Institute of Sport Sciences, University of Lausanne, Lausanne, Switzerland.
Eur J Appl Physiol. 2021 May;121(5):1315-1325. doi: 10.1007/s00421-021-04613-8. Epub 2021 Feb 14.
The effects of muscle contractions on muscle fibre conduction velocity have normally been investigated for contractions of a given duration and intensity, with most studies being focused on the decline on conduction velocity during/after prolonged contractions. Herein, we perform a systematic analysis of the changes in conduction velocity after voluntary contractions of different durations and intensities.
Conduction velocity was estimated in the vastus lateralis before and after knee extensor isometric maximal voluntary contractions (MVCs) of 1, 3, 6, 10, 30 and 60 s, and after brief (3 s) contractions at 10, 30, 50, 70, and 90% of MVC force. Measurements were made during the 10-min period following each contraction.
(1) Conduction velocity was increased immediately after (1 s) the MVCs of brief (≤ 10 s) duration (12 ± 2%, P < 0.05), and then returned rapidly (within 15 s) to control levels; (2) the extent of the increase in conduction velocity was similar after the 3-s, 6-s, and 10-s MVCs (P > 0.05); (3) the magnitude of the increase in conduction velocity after a brief contraction augmented with the intensity of the contraction (increases of 4.6, 7.7, 11.4, 14.8, and 15.2% for contractions at 10, 30, 50, 70, and 90% of MVC force, respectively); (4) conduction velocity was not decreased immediately after the 30-s MVC (P > 0.05); and (5) conduction velocity did not reach its minimum 1 s after the long (≥ 30 s) MVCs.
Brief (≤ 10 s) muscle contractions induce a short-term increase in conduction velocity, lasting 15 s, while long (≥ 30 s) contractions produce a long-term decrease in conduction velocity, lasting more than 2 min.
肌肉收缩对肌纤维传导速度的影响通常是在给定的收缩持续时间和强度下进行研究的，大多数研究都集中在长时间收缩过程中/之后传导速度的下降上。在此，我们对不同持续时间和强度的自愿收缩后传导速度的变化进行了系统分析。
在股外侧肌进行膝关节伸肌等长最大自主收缩（MVC）之前和之后，分别测量 1、3、6、10、30 和 60 秒的传导速度，以及在 10、30、50、70 和 90%MVC 力的短暂（3 秒）收缩后测量传导速度。测量在每次收缩后的 10 分钟期间进行。
（1）持续时间短暂（≤10 秒）的 MVC 后即刻（1 秒），传导速度增加（12±2%，P<0.05），然后迅速（15 秒内）恢复至对照水平；（2）3 秒、6 秒和 10 秒 MVC 后，传导速度的增加幅度相似（P>0.05）；（3）短暂收缩后传导速度的增加幅度与收缩强度成正比（在 10、30、50、70 和 90%MVC 力的收缩中，分别增加 4.6、7.7、11.4、14.8 和 15.2%）；（4）30 秒 MVC 后即刻，传导速度没有降低（P>0.05）；（5）长时间（≥30 秒）MVC 后，传导速度没有在 1 秒后达到最小值。
短暂（≤10 秒）的肌肉收缩会引起 15 秒的短暂传导速度增加，而长时间（≥30 秒）的收缩会导致长时间的传导速度下降，持续时间超过 2 分钟。
