Coherent behavior of neuromuscular oscillations between isometrically interacting subjects: experimental study utilizing wavelet coherence analysis of mechanomyographic and mechanotendographic signals

Figures

• 

  Figure 1. Setting of interacting subjects. Interaction of two subjects during measurement of the abdominal external oblique and triceps brachii muscles and the triceps tendon by piezoelectric MMG-sensors. The signals are conducted across an amplifier to an A/D-converter and are recorded by the software NI DIAdem 10.2 on the measurement notebook (see in26).

• 

  Figure 2. Wavelet spectra. The diagrams show exemplary the wavelet spectra of all three MMG- and MTG-signals of subject (A) (left) and subject (B) (right) during one trial of isometric interaction at 80% of the MVC. The right scale describes the power. The left panel displays the summation of the power in the wavelet spectrum over time, thus, is equivalent to a smoothed PSD.

• 

  Figure 3. Exemplary wavelet coherence spectra (interpersonally). The diagrams show the wavelet coherence spectra of all three MMG- and MTG-signals of one pair (subject A and B) during one trial of isometric interaction at 80% of the MVC. The intensity of coherence (right scale) in the frequency range of 3 to 30 Hz (y-axis) over the time in s (x-axis) is displayed. The black bordered areas show pointwise significant areas of coherence.

• 

  Figure 4. Exemplary wavelet coherence spectra (intrapersonally). The diagrams show the wavelet coherence spectra of the intrapersonal signal pairs of triceps muscle vs. its tendon (above) and of the triceps tendon vs. the abdominal external oblique muscle (bottom) of subject B during isometric interaction of subject A and B at 80% of the MVC.

• 

  Figure 5. Wavelet coherence spectrum of random matched signals. Exemplary coherence wavelet spectrum of two random matched MMG-signals of the triceps muscle of two different subjects (not paired) of different trials during 80% of the MVC. As the spectrum implies, the durations of the coherence patches are significantly shorter than the real pairs. The patches can be interpreted as spurious coherent behavior.

• 

  Figure 6. Coherence parameters of interpersonal pairings. The diagrams show the parameters Sum4Patches (left; in s) and Sum4PaD (right; in %) concerning the wavelet coherence analysis (mean and standard deviation) of the interpersonal measurements at 80% of the MVC, differentiated concerning the signal pairs and sized.

• 

  Figure 7. Sum4Patches and Sum4PaD: real vs. randomly matched pairs. The left panel shows the Sum4Patches, the right one the parameter Sum4PaD between the randomly selected n = 13 real pairs and n = 13 randomly matched pairs at each measuring position (mean and standard deviation) of the trials at 80% of the MVC. *p = 0.000 **p = 0.002 ***p = 0.003.