Linearity and reliability of the mechanomyographic amplitude versus dynamic constant external resistance relationships for the biceps brachii

The purpose of this study was to examine the linearity and reliability of the mechanomyographic (MMG) amplitude versus concentric and eccentric dynamic constant external resistance (DCER) relationships for the biceps brachii. Nineteen healthy men (mean ± SD age = 22.9 ± 2.5 years) performed submaximal to maximal unilateral DCER muscle actions of the dominant forearm flexors on two occasions separated by at least 48 h. During each muscle action, the surface MMG signal was detected from the biceps brachii with an accelerometer. The coefficients of determination ranged from 0.01 to 0.90 for the concentric muscle actions and 0.14 to 0.88 for the eccentric muscle actions, thus demonstrating a wide range of linearity. The intra-class correlation coefficients and standard errors of measurement for the linear MMG amplitude versus DCER slope coefficients were 0.361 (48.0%) for the concentric muscle actions and 0.512 (35.5%) for the eccentric muscle actions, indicating poor reliability. These findings demonstrated that the MMG amplitude versus concentric and eccentric DCER relationships were not consistently linear or reliable.