Differentiation of skeletal muscle fibers into fast and slow twitch appears to be under control of the stimulation pattern imparted by motoneurons innervating these muscle fibers. Fast twitch muscle fibers receive intense stimulation for brief periods of time while slow twitch muscle fibers receive less intense stimulation for much longer periods of time. This study examined thickness of Zlines in dually innervated skeletal muscle fibers of slow twitch soleus muscle following transplantation of the fast extensor digitorum longus (EDL) nerve onto the surface of the soleus. Eight individual dually innervated fibers were dissected from four transplanted mouse soleus muscles and examined with a transmission electron microscope. Z-lines in these dually innervated fibers were thinner (mean = 83 nm) than control soleus (mean = 123 nm) and thicker than control EDL (mean = 57 nm). A significant difference (p< .002) was also found between Z-line thickness near the foreign EDL endplate (mean = 81 nm) versus the original soleus endplate (mean = 85 nm). These results suggest the factors controlling protein synthesis in skeletal muscle fibers have both a global and localized effect. / Department of Physiology and Health Science

A computer model simulating the electrical activity of muscles of the upper arm during elbow motion is presented. The output of the model is an Electromyographic (EMG) signal. System identification is performed on the EMG signals using autoregressive moving average (ARMA) modelling. The calculated ARMA coefficients are then used as the feature set for pattern recognition. Pattern recognition is performed on the EMG signals to attempt to identify which of four possible motions is producing the signal. The results of pattern recognition are compared with results from pattern recognition of real EMG signals. The model is shown to be useful in predicting general trends found in the real data, but is not robust enough to predict accurate quantitative results. Simplifying assumptions about the filtering effects of body tissue, and about the size and position of muscles, are conjectured to be the most likely reasons the model is not quantitatively accurate. / Graduation date: 1992