Beck T W, Housh T J, Johnson G O, Weir J P, Cramer J T, Coburn J W, Malek M H
Department of Nutrition and Health Sciences, Human Performance Laboratory, Center for Youth Fitness and Sports Research, University of Nebraska-Lincoln, Lincoln, Nebraska 68588-0229, USA.
Electromyogr Clin Neurophysiol. 2004 Oct-Nov;44(7):431-41.
The purpose of this investigation was to examine the mechanomyographic (MMG) and electromyographic (EMG) amplitude and mean power frequency (MPF) patterns during fatiguing isokinetic muscle actions of the biceps brachii. Ten adults [three women (mean +/- SD age = 20 +/- 2 yrs) and seven men (mean +/- SD age = 23 +/- 3 yrs) ] volunteered to perform 50 consecutive maximal, concentric isokinetic muscle actions of the biceps brachii at 180 degrees x s(-1). The percent decline (mean +/- SD) in isokinetic peak torque (PT) was 70 +/- 17% and polynomial regression analyses indicated a cubic relationship (R2 = 0.994) between PT and repetition number. Both MMG amplitude and MMG MPF decreased linearly (r2 = 0. 774 and 0.238, respectively) across repetitions. The results for EMG amplitude demonstrated a cubic (R2 = 0.707) pattern across repetitions, where EMG amplitude increased during repetitions 1-20, remained stable during repetitions 20-40, and increased during repetitions 40-50. There was a quadratic (R2 = 0. 939) reduction in EMG MPF throughout the test. The decreases in MMG amplitude and MMG MPF may have been due to de-recruitment of fast fatiguing motor units, a reduction in muscular compliance, or the effects of "muscle wisdom." The results for EMG amplitude may have reflected nonmaximal efforts by the subjects and/or peripheral fatigue. The factor(s) determining the decrease in EMG MPF are unclear, although a reduction in muscle fiber action potential conduction velocity may have been partially responsible.
本研究的目的是检测肱二头肌疲劳等速肌肉运动过程中的肌肉机械肌电图(MMG)和肌电图(EMG)的幅度以及平均功率频率(MPF)模式。十名成年人[三名女性(平均±标准差年龄 = 20±2岁)和七名男性(平均±标准差年龄 = 23±3岁)]自愿以180度/秒的速度连续进行50次肱二头肌最大等速向心肌肉运动。等速峰值扭矩(PT)的下降百分比(平均±标准差)为70±17%,多项式回归分析表明PT与重复次数之间呈三次方关系(R2 = 0.994)。MMG幅度和MMG MPF在重复过程中均呈线性下降(r2分别为0.774和0.238)。EMG幅度的结果显示在重复过程中呈三次方模式(R2 = 0.707),其中EMG幅度在重复1 - 20次期间增加,在重复20 - 40次期间保持稳定,并在重复40 - 50次期间增加。在整个测试过程中,EMG MPF呈二次方下降(R2 = 0.939)。MMG幅度和MMG MPF的下降可能是由于快速疲劳运动单位的失用、肌肉顺应性降低或“肌肉智慧”效应。EMG幅度的结果可能反映了受试者的非最大努力和/或外周疲劳。尽管肌肉纤维动作电位传导速度降低可能部分起作用,但尚不清楚决定EMG MPF下降的因素。