Mechanomyographic responses in quadriceps muscles during fatigue by continuous cycle exercise

Abstract

The present study examined whether the mechanomyogram (MMG) could assess the fatigue-related changes in muscle mechanical properties during cycle exercise. In eight male subjects, the MMG signals were measured in vastus lateralis and rectus femoris by electret condenser microphones. It was found that the integrated MMG (iMMG) showed non linear increase against workload during continuous, incremental cycle exercise and the onset of abrupt changes in iMMG coincided with the ventilatory threshold (VT). Specifically, iMMG in vastus lateralis showed a significant decrement in the rate of increase against workload above VT, reflecting the fatigue-induced impairment of contractile properties of the fibers of active motor units. These results suggest that the MMG measured by electret condenser microphone could be practically used to retrieve the fatigue-related changes in muscle mechanical properties during cycle exercise.

Novel insights into skeletal muscle function by mechanomyography: from the laboratory to the field

“…Eleven studies over twenty used an ACC to detect MMG signal [2,[16][17][18][89][90][91][92][93][94], seven used a PIZ [82,[95][96][97][98][99][100], and two utilized an MIC [101,102].…”

Mechanomyographic responses are not influenced by the innervation zone for the vastus medialis

“…8,9,32,33 For example, Malek and colleagues 9 reported that the patterns of responses for the normalized MMG amplitude were linear (R ¼ 0.933-0.995) for the vastus lateralis and rectus femoris muscles for all subjects (8 of 8) performing a two-legged knee-extensor exercise, but linear (4 of 8), quadratic (3 of 8), or cubic (1 of 8) for those same subjects performing cycle ergometry. Although Kimura et al 34 reported that the MMG amplitude vs. power output was curvilinear during incremental cycle ergometry for the vastus lateralis and rectus femoris muscles, they did not use polynomial regression but instead described the patterns of responses based on the graphical representation of time vs. MMG amplitude. More recently, however, Zuniga et al 18 reported that the MMG amplitude vs. power output relationship differed within each subject (%27% of all subjects) for the proximal and distal sites on the vastus lateralis muscle.…”

The effect of accelerometer mass in mechanomyography measurements

“…Furthermore, MMG MF is associated with muscle fatigue [4, [26][27][28]. It is known that muscle fatigue decreases the MMG MF [26,27]. When the accelerometer mass increases, the reduction in MMG MF can be incorrectly perceived as muscle fatigue.…”

“…According to this model, the natural frequency is inversely proportional to the mass of the spring. Furthermore, MMG MF is associated with muscle fatigue [4, [26][27][28]. It is known that muscle fatigue decreases the MMG MF [26,27].…”