Wavelet-based intensity analysis of the mechanomyograph and electromyograph during the H-reflex

Purpose

The relationship between mechanomyography (MMG) and electromyography (sEMG) during electrically evoked muscle contraction was examined using the von Tscharner “intensity analysis,” which describes the power of a non-stationary signal as a function of both frequency and time.

Method

Data for 8 college-aged participants (3 males; 5 females) with measurable H-reflexes were analyzed. Recruitment curves for H-reflex (H), M-wave (M) using sEMG, and peak-to-peak MMG (MMG_p–p) were elicited through incremental tibial nerve stimulation. The maximum peak-to-peak values for H and M for each sample were summed (HM); and maximum intensity values were measured for MMG, H, and M following the intensity analysis and computation of total intensity (MMG_CvT, H_CvT, M_CvT). H_CvT and M_CvT were subsequently added together (HM_CvT) for comparisons.

Results

Correlations of HM:MMG_p–p, HM:MMG_CvT, HM_CvT:MMG_CvT, HM_CvT:MMG_p–p, were low (r = 0.34, 0.33, 0.09, and 0.12, respectively, p < 0.001); and correlations of HM:HM_CvT, MMG_CvT:MMG_p–p, were moderate-to-high (r = 0.69 and 0.97, respectively, p < 0.001). Correlations for individuals ranged from 0.61 to 0.99 across comparisons. The time at which maximal intensities occurred reflected the transition from a predominant H-reflex to the onset of the M-wave and declining lag times were noted with increasing intensity.

Conclusions

The intensity analysis provides insight into the frequency characteristics of the H-reflex and M-wave not seen in traditional analysis of the H-reflex. The intensity analysis may be a useful tool in studying individual variations and changes in the contraction velocities of skeletal muscle.