膝关节伸肌最大等速向心和离心收缩运动前后神经肌肉疲劳的研究

A Study on the Neuromuscular Fatigue before and after Maximal Isokinetic Concentric and Eccentric Contractions of Knee Extensor

目的:采用电刺激检测技术对膝关节伸肌最大等速向心和离心收缩运动后神经肌肉功能进行检测,探索向心和离心收缩运动前后神经肌肉疲劳的变化及产生部位。方法:15名青年男性受试者在等速肌力测试仪(Iso Med 2 000)上分别完成膝关节伸肌最大等速向心收缩运动和离心收缩运动试验(角速度:60(°)/s;5组×10次,组间间歇时间1 min;离心收缩运动试验在向心收缩运动试验1周后进行)。每次试验前后测量受试者最大随意收缩力量(MVC),记录运动过程中每次收缩平均力矩和平均做功的值;运动前后使用电刺激检测技术对受试者进行神经肌肉功能检测,对MVC、RFD-MVC、Pt、RFD-Pt、RHR-Pt、Pt10/Pt100及中枢激活水平Va进行提取和分析。结果:(1)在离心收缩运动过程中各组平均力矩和平均做功显著高于向心收缩运动(P<0.01);膝关节平均力矩和平均做功在向心收缩运动过程中随运动持续呈下降趋势,在离心收缩运动过程中呈上升趋势,但变化均不显著(P>0.05)。(2)向心收缩运动后MVC由运动前(277.05±54.21)Nm下降到(231.14±48.49)Nm(P<0.01),离心收缩运动后MVC由运动前(276.14±43.21)Nm下降到(252.85±31.45)Nm(P<0.05)。(3)向心收缩运动后Pt由运动前(58.23±9.25)Nm下降到(46.07±9.32)Nm(P<0.01),离心收缩运动后Pt由运动前(58.52±10.01)Nm略上升为(59.07±4.57)Nm,二者无显著性差异(P>0.05)。向心收缩运动后Pt10/Pt100无显著性变化,离心运动后Pt10/Pt100由运动前106.10±8.47下降为91.81±3.8(P<0.01),Pt10/Pt100下降率为(13.47±2.76)%,显著高于向心运动Pt10/Pt100的下降率(P<0.01)。(4)向心收缩运动后Va由运动前(80.92±5.31)%下降至(78.78±1.41)%(P<0.05),离心收缩运动后Va由运动前(81.10±3.54)%下降至(75.62±1.01)%(P<0.01),离心收缩Va下降率为(6.90±0.98)%,显著高于向心收缩运动后Va的下降率(2.66±0.63)%(P<0.05)。结论:膝关节伸肌50次最大等速向心、离心收缩运动过程中,离心收缩肌肉做功高于向心收缩,且离心收缩力矩高于向心收缩力矩,表明离心收缩运动可能比向心收缩运动更耐疲劳;向心、离心运动后肌肉产生明显神经肌肉疲劳,且向心收缩运动后疲劳程度高于离心收缩运动;向心收缩运动的外周疲劳程度高于离心收缩运动,离心收缩运动的中枢疲劳程度更大。

Objective：Electrical stimulation test was used to detect the neuromuscular function after maximal isokinetic concentric and eccentric contraction ofknee extensors,and to explore the changes of neuromuscular fatigue before and after concentric and eccentric contraction exercises and the site of their produc-tion. Methods：Fifteen young male subjects completed respectively maximal isokinetic concentric contraction and eccentric contraction exercises（angular veloci-ty：60（°）/s;5 groups×10 repetitions,1 min of intermittent interval;the eccentric contraction exercise experiment was performed one week after the concentriccontraction exercise experiment）of knee extensor muscle on the isokinetic dynamometer（Iso Med2000）.The maximal voluntary contraction torque（MVC）of thesubjects was measured before and after each experiment,and the average torque and work of each contraction during the exercise was recorded. The neuromuscu-lar function of the subjects was measured by electrical stimulation before and after exercise. The related indexes such as MVC,RFD-MVC,Pt,RFD-Pt,RHR-Pt,Pt10/Pt100 and voluntary activation（Va）were extracted and analyzed. Results：1）In the process of eccentric contraction,the average torque and average workof each group were significantly higher than those of the concentric contraction respectively（P0.01）;The average torque and work in the process of concentriccontraction exercise showed downtrend along with the continuing exercise,while showed uptrend in the process of eccentric contraction exercise,but no signifi-cant change（P0.05）.2）The MVC was reduced to（231.14±48.49）Nm from（277.05±54.21）Nm（P0.01）after the concentric contraction,and reduced to（252.85±31.45）Nm from（276.14±43.21）Nm（P0.05）after eccentric contraction.3）The Pt decreased from（58.23±9.25）Nm to（46.07±9.32）Nm（P0.01）afterconcentric contraction,and slightly increased from（58.52 ± 10.01）Nm to（59.07±4.57）Nm after eccentric contraction with no significant difference（P0.05）.Pt10/Pt100 decreased significantly from 106.10±8.47 to 91.81±3.8（P0.01）after eccentric contraction,and the decrease rate of Pt10/Pt100 was（13.47±2.76）%,which was significantly higher than that decrease rate of Pt10/Pt100 after concentric exercise（P0.01）.4）The Va decreased from（80.92±5.31）% to（78.78±1.41）%（P0.05）after concentric contraction,and decreased from（81.10±3.54）% to（75.62±1.01）%（P0.01）after eccentric contraction. The decreaserate of Va after eccentric contraction was（6.90±0.98）%,which was significantly higher than that（2.66±0.63）%,the decrease rate of Va after concentric con-traction（P0.05）. Conclusions：In the process of knee extensor isokinetic 50 maximum concentric and eccentric contraction exercises,the muscle work of eccen-tric contraction is higher than that of concentric contraction,and the torque produced by eccentric contraction higher than that of concentric contraction,indicat-ing that eccentric contraction may be more fatigue resistible than concentric contractions;both concentric and eccentric contractions after exercise produced sig-nificant neuromuscular fatigue,and the fatigue extent produce by concentric contraction was higher than that produce by eccentric contraction;The peripheral fa-tigue extent produce by concentric contraction was higher than that produce by eccentric contraction;The central fatigue extent produce by eccentric contractionwas higher than that produce by concentric contraction.