Optimized peripheral tremor suppression could address many limitations of surgical or medicinal treatments of Essential Tremor, however it is not well understood how the tremorogenic activity is distributed among the muscles of the upper limb, and therefore how to optimize such suppression. We recorded electromyographic (EMG) activity in the 15 major superficial muscles from the shoulder to the wrist while subjects performed postural and kinetic tasks similar to activities of daily living. We calculated the power spectral density and computed the total power in the tremor band (4"12 Hz) for each muscle, from which we determined the distribution of tremorogenic activity among the 15 muscles for various conditions. Differences in distribution between conditions were quantified as Pearson correlation coefficients. All 15 muscles exhibited some tremorogenic activity. The anterior deltoid exhibited by far the most power, the wrist extensors had more power than other distal muscles, and the triceps longus showed the least power. Distributions among muscles was highly consistent across repetitions (r = 0.91 ± 0.07) and somewhat stereotyped across subjects (r = 0.58 ± 0.31). Differences in task (postural vs. kinetic), limb configuration, and subject characteristics (sex; tremor severity, onset, and duration) had little effect on distribution (r =0.84). Interestingly, the distribution of tremorogenic activity was highly correlated (r = 0.94 ± 0.08) with the distribution of voluntary activity (power between 0.5 and 4 Hz). In particular, muscles opposing gravity had the highest amount of tremorogenic activity. This may explain in part why the distribution of tremorogenic activity was stereotyped across subjects.
College and Department
Ira A. Fulton College of Engineering and Technology; Mechanical Engineering
BYU ScholarsArchive Citation
Standring, David Jordan, "Distribution of Tremorogenic Activity among the MajorSuperficial Muscles of the Upper Limb inSubjects with Essential Tremor" (2019). Theses and Dissertations. 7557.
essential tremor, EMG, tremor distribution, upper limb, PSD