Goodall Stuart, Charlton Kayleigh, Howatson Glyn, Thomas Kevin
1Faculty of Health and Life Sciences, Department of Sport, Exercise and Rehabilitation, Northumbria University, Newcastle, UNITED KINGDOM; and 2Water Research Group, School of Environmental Sciences and Development, Northwest University, Potchefstroom, SOUTH AFRICA.
Med Sci Sports Exerc. 2015 Mar;47(3):528-36. doi: 10.1249/MSS.0000000000000443.
This study aimed to determine the pattern of neuromuscular fatigability that manifests during repeated-sprint running exercise.
Twelve male participants (mean ± SD: age, 25 ± 6 yr; stature, 180 ± 7 cm; body mass, 77 ± 7 kg), currently training and competing in intermittent sprint sports, performed a repeated maximal sprint running protocol (12 × 30 m, 30-s rest periods). Pre- and postexercise twitch responses to transcutaneous motor point stimulation and transcranial magnetic stimulation were obtained to assess knee extensor neuromuscular and corticospinal function, respectively. Throughout the protocol, during alternate rest periods, blood lactate samples were taken and a single knee extensor maximal voluntary contraction (MVC) of the knee extensors was performed, with motor point stimulation delivered during and 2 s after, to determine voluntary activation (VA) and peripheral fatigue.
The repeated-sprint protocol induced significant increases in sprint time and blood [lactate] from the third sprint onwards (P < 0.001). Furthermore, knee extensor MVC, resting twitch amplitude, and VA were all significantly reduced after two sprints and reached their nadir after sprint 10 (Δ12%, Δ24%, Δ8%, P < 0.01, respectively). In line with a reduction in motor point-derived VA, there was also a reduction in VA measured with transcranial magnetic stimulation (Δ9%, P < 0.05) immediately after exercise.
These data are the first to demonstrate the development of neuromuscular fatigability of the knee extensors during and immediately after repeated-sprint exercise. Peripheral and central factors contributing to muscle fatigability were evident after two maximal sprints, and over half of the drop in postexercise MVC was due to supraspinal fatigue. Thus, peripheral, central, and supraspinal factors all contribute to the performance decrement and fatigability of the knee extensors after maximal repeated-sprint activity.
本研究旨在确定重复冲刺跑运动中表现出的神经肌肉疲劳模式。
12名男性参与者（平均±标准差：年龄，25±6岁；身高，180±7厘米；体重，77±7千克），目前从事间歇性冲刺运动的训练和比赛，进行重复最大冲刺跑方案（12次×30米，休息30秒）。运动前和运动后分别通过经皮运动点刺激和经颅磁刺激获得抽搐反应，以评估膝伸肌神经肌肉功能和皮质脊髓功能。在整个方案中，在交替的休息期间，采集血乳酸样本，并对膝伸肌进行单次最大自主收缩（MVC），在收缩期间和之后2秒进行运动点刺激，以确定自主激活（VA）和外周疲劳。
从第三次冲刺开始，重复冲刺方案导致冲刺时间和血乳酸显著增加（P<0.001）。此外，两次冲刺后膝伸肌MVC、静息抽搐幅度和VA均显著降低，并在第10次冲刺后达到最低点（分别为Δ12%、Δ24%、Δ8%，P<0.01）。与运动点衍生的VA降低一致，运动后立即经颅磁刺激测量的VA也降低（Δ9%，P<0.05）。
这些数据首次证明了重复冲刺运动期间及之后立即出现的膝伸肌神经肌肉疲劳的发展。两次最大冲刺后，导致肌肉疲劳的外周和中枢因素明显，运动后MVC下降的一半以上是由于脊髓上疲劳。因此，外周、中枢和脊髓上因素均导致最大重复冲刺活动后膝伸肌的性能下降和疲劳。
