Jotta Bruno, Cavalcanti Garcia Marco Antonio, Visintainer Pino Alexandre, De Souza Marcio Nogueira
Laboratório de Instrumentação Biomédica (LIB) - PEB/COPPE/UFRJ, Cidade Universitária, Ilha do Fundão, Rio de Janeiro, Brazil.
Departamento de Biociências da Atividade Física - EEFD/UFRJ Cidade Universitária, Ilha do Fundão, Rio de Janeiro, Brazil.
Acta Bioeng Biomech. 2015;17(4):73-84.
Lateral (X) and longitudinal (Y) mechanical oscillations of muscle fibers that take place during muscular contraction seem to contain information additionally to the myoelectric activity, which can contribute to the interpretation of some muscle gradation force mechanisms. However, no previous study was found that had investigated the relationship between the muscle force and features associated to the mechanomyographic (MMG) signal obtained by means of a biaxial accelerometer in three different muscles. Therefore, the aim of this study was to evaluate the relationship between the force output at different load levels (20% to 100%) of the maximum voluntary isometric contraction (%MVIC) and the two signals supplied by a biaxial accelerometer and, in addition, the so-called resultant (R) acceleration signal derived from the two signals mentioned previously. Twenty seven male volunteers participated in this study.
The force output related to the right biceps brachii, soleus and gastrocnemius medialis muscles was studied by means of linear regression models fit to log-transformed of the root mean square (RMS) values of the MMG signals in X, Y, and R axes versus each %MVIC. The phase angle of R acceleration (PhaseR) and anthropometric data were also considered.
The angular coefficient a and the antilog of y-intercept b from the log-transformed of MMG data values versus force output were able to distinguish partially motor unit strategies during isometric contractions in the three muscles studied.
The findings suggest that biaxial accelerometer seems to be an interesting approach in the assessment of muscle contraction properties.
肌肉收缩过程中肌肉纤维的横向（X）和纵向（Y）机械振荡似乎除肌电活动外还包含信息，这可能有助于解释某些肌肉分级力机制。然而，未发现之前有研究调查过在三种不同肌肉中通过双轴加速度计获得的机械肌电图（MMG）信号相关特征与肌肉力量之间的关系。因此，本研究的目的是评估在最大自主等长收缩（%MVIC）的不同负荷水平（20%至100%）下的力输出与双轴加速度计提供的两个信号之间的关系，此外还包括从上述两个信号导出的所谓合成（R）加速度信号。27名男性志愿者参与了本研究。
通过将MMG信号在X、Y和R轴上的均方根（RMS）值进行对数转换后，与每个%MVIC进行线性回归模型拟合，研究与右侧肱二头肌、比目鱼肌和腓肠肌内侧肌肉相关的力输出。还考虑了R加速度的相位角（PhaseR）和人体测量数据。
MMG数据值的对数转换后与力输出的角系数a和y轴截距b的反对数能够部分区分所研究的三块肌肉在等长收缩期间的运动单位策略。
研究结果表明，双轴加速度计似乎是评估肌肉收缩特性的一种有趣方法。
