Beck T W, Housh T J, Fry A C, Cramer J T, Weir J P, Schilling B K, Falvo M J, Moore C A
Department of Nutrition and Health Sciences, Human Performance Laboratory University of Nebraska-Lincoln Lincoln, Nebraska 68583-0806, USA.
Electromyogr Clin Neurophysiol. 2007 Jul;47(4-5):221-32.
The purpose of this investigation was to examine the influence of muscle fiber type composition on the patterns of responses for electromyographic (EMG) and mechanomyographic (MMG) amplitude and mean power frequency (MPF) during a fatiguing submaximal isometric muscle action. Five resistance-trained (mean +/- SD age = 23.2 +/- 3.7 yrs) and five aerobically-trained (mean +/- SD age = 32.6 +/- 5.2 yrs) men volunteered to perform a fatiguing, 30-sec submaximal isometric muscle action of the leg extensors at 50% of the maximum voluntary contraction (MVC). Muscle biopsies from the vastus lateralis revealed that the myosin heavy chain (MHC) composition for the resistance-trained subjects was 59.0 +/- 4.2% Type IIa, 0.1 +/- 0.1% Type IIx, and 40.9 +/- 4.3% Type I. The aerobically-trained subjects had 27.4 +/- 7.8% Type IIa, 0.0 +/- 0.0% Type IIx, and 72.6 +/- 7.8% Type I MHC. The patterns of responses and mean values for absolute and normalized EMG amplitude and MPF during the fatiguing muscle action were similar for the resistance-trained and aerobically-trained subjects. The resistance-trained subjects demonstrated relatively stable levels for absolute and normalized MMG amplitude and MPF across time, but the aerobically-trained subjects showed increases in MMG amplitude and decreases in MMG MPE The absolute MMG amplitude and MPF values for the resistance-trained subjects were also greater than those for the aerobi-cally-trained subjects. These findings suggested that unlike surface EMG, MMG may be a useful noninvasive technique for examining fatigue-related differences in muscle fiber type composition.
本研究的目的是检验在次最大等长肌肉疲劳动作期间，肌纤维类型组成对肌电图（EMG）和肌机械图（MMG）振幅及平均功率频率（MPF）反应模式的影响。五名进行抗阻训练的男性（平均±标准差年龄 = 23.2±3.7岁）和五名进行有氧训练的男性（平均±标准差年龄 = 32.6±5.2岁）自愿参与，以最大自主收缩（MVC）的50%进行腿部伸肌的30秒次最大等长疲劳肌肉动作。来自股外侧肌的肌肉活检显示，抗阻训练受试者的肌球蛋白重链（MHC）组成中，IIa型占59.0±4.2%，IIx型占0.1±0.1%，I型占40.9±4.3%。有氧训练受试者的MHC组成中，IIa型占27.4±7.8%，IIx型占0.0±0.0%，I型占72.6±7.8%。在疲劳肌肉动作期间，抗阻训练和有氧训练受试者的绝对和标准化EMG振幅及MPF的反应模式和平均值相似。抗阻训练受试者的绝对和标准化MMG振幅及MPF随时间表现出相对稳定的水平，但有氧训练受试者的MMG振幅增加，MMG MPE降低。抗阻训练受试者的绝对MMG振幅和MPF值也高于有氧训练受试者。这些发现表明，与表面肌电图不同，肌机械图可能是一种用于检查肌纤维类型组成中与疲劳相关差异的有用非侵入性技术。
